START Magazine/START VOL 3 NO 8.st/SEURDOCS.ARC/SEURAT.DOC

Text File | 1988-12-07 | 107.7 KB | 2,089 lines

U S E R ' S    G U I D E   for   S E U R A T
Copyright 1988, by S. K. Webb, SKWare One, Inc.

                       WHAT YOU NEED TO RUN SEURAT

    SEURAT requires the SEURAT.DAT file to run. It must be in the root
directory of whatever disk it is on. The program disk may also contain
whatever folders you wish, but folders may be placed on the data disk
containing your images, or on a disk of their own. The first thing
SEURAT does when it is loaded is to load in data from the SEURAT.DAT
file. After this is accomplished and the main menu is displayed, the
data file will not be needed again until the next time you load SEURAT.
The disk may then be changed for a data disk for images.

    The other thing you need to do is to read this manual at least
once, however cursorily, before attempting to use SEURAT.  Please...

MAIN MENU

    After data-loading is complete, SEURAT presents the user with the
main menu from which all functions of the program are accessible. The
currently selected image, or paint screen, is displayed by clicking the
right mouse button or by pressing Escape. You may return to the main
menu from the paint screen by the same means: clicking the right mouse
button or by pressing the Escape (with certain exceptions noted below).

    In low resolution, the main menu displays fill the screen. In
medium and high resolutions, these same buttons and options leave a
considerable portion of the center of the menu screen available for a
view window, configured much like the zoom screen view window, through
which the currently active paint screen can be seen.

    Forty-six fill patterns are displayed around the border of the main
menu. The currently active fill pattern is shown in the active fill
selection display, which is located at the central left-hand edge of
the screen.

    Immediately to the right of this active fill selection display is a
stack of four buttons:  COLOR and MONO, which toggle the peripheral
display of 46 fill patterns between the two fill types, the TEXT button
and a button that calls a pop-out menu, which will appear over the
brush selector boxes.

    Below the active fill display are the buttons for setting the WRITE
MODE, and above it the buttons for selecting a paint function or
operation.

    To the right of this block of buttons is a vertical column of
buttons labeled A through H. These are the paint screen selector boxes.

    In the upper right-hand portion of the main menu is the palette
display. The colors are arranged from the screen background color
(color 0) at the upper-left to the writing color (color 15, or 3, or 1,
depending on the resolution) at the lower-right.

    Just below the currently active palette is the FRE memory line, a
continuously updated register showing the program's available free
memory in decimal numbers.

    Below the FRE ledger line are three buttons controlling the INK,
CLIP and AUTO functions. Beneath them, in the lower right-hand area of
the main menu are the brush selector boxes.

    The current selection of functions and operations are shown by
highlighting the buttons in the usual GEM manner. There should always
be one paint function (or text) button, one currently selected write
mode, one active brush selection, one active paint screen selection,
and one fill type selection highlighted at all times.

    The actual relative placement of the buttons and features of the
main menu varies somewhat with the resolution in which the program is
running. The low resolution screen is quite full, the medium less
crowded, and the high resolution menu screen is rather sparsely
settled.

    A detailed description of all features follows:

    VIEW WINDOW: The view window displays a 5:4 upright rectangle which
reveals 25.1% of the paint screen. The view window can be scrolled up,
down, left and right one pixel at a time by clicking on the directional
arrows in the corner boxes of the view window border. (Note: The arrows
refer to the direction of movement of the window, not the movement of
image in the window.)

    The view window can also be shifted much more rapidly by dragging
with the left mouse key on the vertical or horizontal sliders seen in
the upper and left-hand portions of the view window's border. (Note:
the sliders alone are not able to reach the last few pixels at the edge
of the paint screen, but the arrows can shift the image to the very
edge. In general, some "fine tuning" by the arrows is necessary for
precision positioning.)

    The X and Y coordinates of the upper-left-hand corner of the
screen area which is currently displayed in the view window are shown
in the lower border of the view window.

    CURSORS: SEURAT's cursor shapes are configured to provide the user
with status information. The cursor configuration alters according to
the routine in which the user is operating: the file cursor in file
functions, the grid cursor in the grid color changing routine, the
palette cursor in palette mode, etc. Specific cursor shapes are
described in each appropriate section below.

    Additionally, there is a cursor that is "normal" in form but that
contains the currently selected color.

    WRITE MODE: There are four write modes available for graphic
operations on the ST. All user graphic operations except block placements
are carried out in the user's currently selected write mode.

    The four modes are:

    1) OVERWRITE (which GEM calls replace), in which all new pixels
replace any existing pixels that might be present at that screen
location.

    2)  TRANSPARENT, in which all new pixels of color 1 or higher
replace existing pixels, but new pixels of the screen background color
(color 0) are treated as "transparent," allowing existing old pixels to
"show through;" that is, they are not replaced.

    3) XOR (Exclusive Or), in which the new pixel is xor'ed with the
existing pixel. The rule of the xor is: one or the other but not both.
Or, 1 xor 1 = 0, 1 xor 0 =1, 0 xor 1 = 1, and 0 xor 0 = 0 (at least in
monochrome; the results are less predictable in color).

    (Note: xor behaves differently in block placements than in the
other graphic operations, because of the distinction made between 0
pixels that have been set to 0 and 0 pixels that have not been set; see
below.) The chief usefulness of xor lies in the fact that a bit pattern
xor'ed to the same place twice restores the original pattern of pixels
present before the two operations.

    4) REVERSE TRANSPARENT, in which new set pixels which overlap old
set pixels are unset (color 0) and unset pixels are transparent with
regard to old set pixels. It is the "reverse" of the transparent mode.

    If the write modes sound confusing to the user, don't be too
discouraged, because they are both confusing and confused! Complicating
the picture is the that that GEM distinguishes between set and unset
pixels. That's no problem, unless you're talking about pixels of the
screen background color (color 0). Oddly enough, the distinction
between set and unset color 0 pixels is only observed in operations on
blocks, where unset pixels are ignored, while in all other operations,
all pixels of color 0, set and unset alike, are affected. I cannot say
whether this is a pecularity of GFA BASIC or GEM itself.

    From a practical standpoint, the thing to do is play around with
the effect of each write mode on the operations you perform, as it is
often difficult to predict what the result will be. Experiment with the
many combinations, as some startling effects are possible.

    The write mode may be set on the main menu by clicking on one of
the four write mode selector buttons. Write mode may also be set or
altered any number of times during a graphic operation (that is, while
the paint screen is displayed) by pressing the 1, 2, 3 or 4 keys on the
keyboard. (Keypresses are valid only while the paint screen is "up,"
not from the main menu. Please note the single exception: the write
mode cannot be changed by keypress while you are entering text, since
keypresses in the text routine are routed to the text string, except
for Escape and Backspace.)

    Selecting the TEXT operation or choosing BLOCK as the paint
operation automatically toggles the write mode to transparent, the most
usual choice for those operations. However, the write mode may be
reset at any time. The write mode is not toggled back when another
option besides block or text is selected; it must be reset by the user.

    BLOCK: The block function allows the user to "get" a piece of the
paint screen and place it somewhere else on that paint screen or on
another paint screen. When you first toggle on the block function and
go to the paint screen, the mouse will be replaced by a full screen
cross-hair cursor.

    Placing the cursor center (where the two lines cross) and pressing
and holding the left mouse button will mark the upper-left-hand corner
of the block you are selecting. Still holding the left mouse button
down, drag the mouse down and away (to the right) to where you want the
lower-right-hand corner of the block to be. A box will be dragged
around the block as you do so.

    When you release the left mouse button, a copy of that portion of
the paint screen will be "cut out" as a block. In low and medium
resolutions, the mouse will briefly reappear as the "busy bee" while
the program unleaves the bit planes of the image and combines them to
construct a monoplane mask of the block. In high resolution this
operation is unnecessary (since the image is already monoplane), so
there is virtually no delay. The time delay varies inversely with the
size of the block and the number of bit planes to be combined, but the
slight delay is hardly noticeable until you "pull" a block larger than
a quarter-screen or so.

    When masking is complete, a free-floating copy of the block
appears, attached at its center to the cursor point. This free-floater
is shown in the transparent mode, for a maximally unobstructed view of
the rest of the paint screen, regardless of which write mode is
currently selected.

    In monochrome, the transparent "floater" can become entirely
invisible, particularly when it is on a large area of not-the-screen-
background color. To avoid this problem, press the Help key. This will
toggle the floater into being displayed in the overwrite mode (regardless
of which write mode is selected; the selected write mode remains active),
thus making it visible everywhere on the screen. Another press of the
Help key will toggle the floater back to transparent display, and so
forth. The Help key works (and is necessary) this way only in high
resolution when block is the paint function, as it key has another
function in all other operations.

    Once you have the block as a floater, you may place it wherever you
wish. The block can be moved off the edge of the paint screen (as far
as its midpoint) in any direction. A single click of the left mouse
button will affix a copy of the block (or that portion on the screen)
at its current location. The block will printed to the paint screen in
whatever write mode you have selected.

    As mentioned earlier, the four write modes available generally
throughout SEURAT for graphic operations are not implemented in the
same manner for block placement. Overwrite and transparent function in
the same manner as for graphic operations, but the xor mode affects
only set pixels and is not executed on unset pixels.

    Because a true reverse transparent write mode would be of limited
usefulness for block placement, SEURAT substitutes inverse transparent
as the fourth write mode for blocks. In the inverse transparent mode,
he block is printed to the screen transparently (with pixels of color 0
"transparent" to the background) but with the set pixels printed in
inverse (If color>0 Then NOT Color).

    Additionally, if you press the 4 key in a for the inverse transparent
mode and then hold down the Alternate key while placing the block with a
left mouse click, the block will be printed to the paint screen in the
not transparent mode (the block is "transparent" to the background, but
the background that "shows through" is printed in inverse (not color) as
well as the set pixels of the block).

    These two new write modes more than make up for the absence of the
not-terribly-useful (for blocks) reverse transparent mode. A wide range
of graphically intriguing effects are possible with the inverse
transparent and not transparent modes. Experiment with them!

    Additionally, it is often very useful to have user access to the
block mask alone, without the accompanying block. For example, in the
case when the block has a number of transparent "holes" which are
supposed to be dark shadows in the image, but through which a bright
distracting background shows. Holding down the Control key while
placing a block will result in the block mask alone being printed to
the screen in whichever write mode is currently selected (in write mode
4, an inverse mask is printed). Thus, one can "paste" a copy of the
mask to an empty paint screen (with the same palette), fill in the
"holes" quickly with a brush, fill the mask with a dark color, "pull"
the mask as a block itself, use it to black out the background in the
position where the desired block is to be placed, go "pull" the desired
block, and align it over the black-out mask to produce a shadow.

    Those familiar with the ST will know that placement of screen
portions is implemented by means of sixteen "primitive" graphic modes,
in which two screen areas are combined according to variety of logical
operations. These 16 modes can be selected for block operations by
pressing the keys A through P (either upper or lower case permitted).

    Again, holding down the Control key while clicking with the left
mouse button will result in the block mask, rather than the block,
being placed in whichever of the sixteen modes you have selected.

    This A-through-P key press is a one-time only operational mode;
only the next block placement after such a key press is performed in
one of the sixteen logical modes. These logical modes are as follows:

        A (0) - DELETE DESTINATION AREA
        B (1) - NEW AND OLD
        C (2) - NEW AND (NOT OLD)
        D (3) - NEW {OVERWRITE}
        E (4) - (NOT NEW) AND OLD {IMP}
        F (5) - OLD {DO NOTHING}
        G (6) - NEW XOR OLD
        H (7) - NEW OR OLD
        I (8) - NOT (NEW OR OLD) {NOR}
        J (9) - NOT (NEW XOR OLD) {EQV}
        K (10) - NOT OLD {INVERSE}
        L (11) - NEW OR (NOT OLD)
        M (12) - NOT NEW {INVERSE OVERWRITE}
        N (13) - (NOT NEW) OR OLD
        O (14) - NOT (NEW AND OLD) {NAND}
        P (15) - SOLID COLOR 1 FILL DESTINATION AREA

    Further copies of the block can be placed elsewhere. If you return
to the main menu and switch paint screens, when you enter the new paint
screen, the block will follow (as long as you are still in the block
function), and copies may be placed there or in any paint screen.

    Pressing the Escape key indicates that you wish to select another
block. The full-screen cross-hair cursor will reappear and the process
may be repeated. The selection of a new block may take place in any
paint screen, but you must have selected the block function to do so.

    Blocks, once placed, can be removed from the paint screen by
pressing Undo. Repeated keypresses of the Undo key will progressively
remove blocks in the inverse order of their placement. Block Undo
utilizes its own stack memory for block erasure. In order to conserve
free memory, the block undo stack can be cleared after a succesion of
operations by pressing Backspace. This must be done while block is the
active paint function and while the paint screen is up, rather than the
main menu is showing). For a complete description of how the block undo
works, read the section on ERASE AND UPDATE carefully (below).

    Blocks may be manipulated in a variety of ways. They may be
rotated, resized, and mapped to skew lines, arcs, distorted (in one
dimension) in a freeform fashion, distorted trapezoidially in one
dimension or the other, or in both dimensions at once. The complete
description of block manipulations is to be found in the section on the
BLOCK MENU (below).

    To return to the main menu, press the right mouse button (not
Escape, which would select a new block!).

    FILL: Place the cursor at any point on the paint screen and press the
left mouse button down firmly. Beginning at that point and proceeding in
all directions from it, portions of the paint screen having the same
color value as the selected point and continuously connected to it will
be printed in the currently active fill pattern.

    Fill can easily leak into an area through diagonal gaps or staggers
in a drawn figure, flooding it with fill. Immediately before executing
a fill is a good time to update the paint screen with the Insert key,
so that a faulty fill or series of fills can be undone. Consult the
section on ERASE AND UPDATE for the operation of Insert-Undo.

    A right mouse click or pressing Escape returns you to the main
menu.

    FILL SELECTION: A fill pattern may be selected by clicking on the
appropriate box from the 46 fill display boxes around the circumference
of the main menu. Only one fill type is shown at a time (COLOR or
MONO). The user may change the fill type by a left mouse click on the
COLOR or MONO buttons, which will trigger a redraw of the fill patterns
to that fill type.

    The status of the INK option also effects the selection of fill
pattern, by toggling the fill selection to MONO solid fill (number 7).
See the explanation of INK given below. (Note: fills referred to by
number in this manual are numbered from the upper-left-hand corner,
proceeding clockwise around the main menu. The numbers used are 0 to
45.)

    The first 36 mono fills are those supplied by GEM. The remaining
mono fills and all the color fills are built into SEURAT. All 92 fills
are also included in the fill disk files, so that any fills replaced
during the course of program operation can be reloaded if needed. The
first color fills are "toners," i.e., half-tone patterns of Colors 1
through the color just below the writing color mixed with the writing
color itself. A separate set of color fills are supplied by SEURAT for
operations in medium resolution; the medium resolution toners are
combinations of all four colors with each other.

    Fills, whether in filled figures or used as area fills, are printed
to the screen in the currently selected write mode, hence it is
possible to fill one fill pattern with another fill pattern, to
"overlay" an image with a "transparent" fill. Monoplane fills in a
variety of colors can be combined with each other. Color fills as well
as monoplane fills are printed in the currently selected write mode,
thus a color fill which contains a background of the screen background
color may be utilized in transparent mode.

    Again, as the effect of different write modes on fill patterns is
far from predictable, I suggest you experiment with a variety of
combinations of effects.

    A left mouse double-click on the COLOR or MONO buttons calls up the
appropriate color or mono fill editor, which allows fill patterns to be
created, erased, modified, shifted, inverted, flipped, and SAVEd to and
LOADed from disk.

    For a complete description, see the section on the FILL EDITOR
(below).

    FILL EDITOR: Double-clicking on either the COLOR or the MONO fill
type selector button calls up the appropriate fill editor. It consists
of a) a 16x16 enlarged pixel input screen, b) seven function buttons,
c) an  actual-size fill display and d) a color selector.

    When the fill editor is called, it loads the currently selected
fill pattern into the input screen, where the user can modify it. A
left mouse click on one of the color selectors lets the user draw on
the input screen in that color with the left mouse button. The mouse
changes color to show the color selected. The right mouse button will
erase an enlarged pixel on the input screen by converting it to the
screen background color.

    The altered fill pattern is displayed in its actual size and in
sufficient multiples for the user to gauge its appearance in a fill
display box to the lower-right of the input screen. The fill display is
updated as the fill pattern is altered. The color selector boxes are
arranged from the screen background color at the top to the writing color
at the bottom.

    Color fill patterns are palette dependent; that is, they change
with every change in the palette that involves the colors of which they
are composed. Thus, color fills may have to be edited for their best
appearance in any image with a different palette than the default
palette. SEURAT speeds the process of reassigning colors with the AUTO
COLOR CHANGE feature.

    Double-clicking on one of the color selectors causes every pixel in
the fill pattern which is the selected color (the color of the cursor)
to be redrawn in the color the user double-clicked on. These changes
are made both on the input screen and in the actual size fill display.
Note that the cursor color has not been changed. Remember: that's
single-click on the color to be changed, and double-click on the color
to change it to.

    Fill patterns may be geometrically manipulated. Clicking on the
INVERT button causes the fill pattern to be inverted, that is, turned
upside down. Clicking on the FLIP button reverses the fill pattern from
left-to-right. Additionally, the four cursor keys will shift the fill
pattern one pixel in their direction. The ERASE button will clear the
fill pattern.

    Fill patterns are SAVEd to disk as a 16-word-per-bit-plane string.
Hence, mono-plane fills (file extension .FIL) take 32 bytes, medium
resolution two-plane fills (file extention .FL2) take 64 bytes, and low
resolution four-plane fills (file extension .FL1) are 128 bytes in
length.

    Fill patterns may also be SAVEd to or LOADed from disk. (For numerous
small files such as these, folders are practically a neccessity; however,
SEURAT does not require them.)

    Once a fill pattern has been modified or created, clicking on OK
will cause the new fill to become the active fill pattern. It replaces
the fill pattern that was selected when the user entered the fill
editor.

    CANCEL aborts all changes made and restores the fill to that fill
pattern which was selected before entering the fill editor.

    The fill editor functions identically in MONO and COLOR fill types,
except, of course, that in MONO only the screen background color and
the writing color are active.

    BRUSH:  The "brush" is a geometric pattern of pixels which can be
painted to the screen. In the lower right-hand corner of the main menu
is an array of brush selector boxes. The default brush is the minimum
brush: a single pixel. This option might be called "Pencil" or "Draw"
in another program.

    When the brush function is active, the paint screen cursor is a
"register mark," or an open cross-hair, which can be seen on any color
background. The brush shape itself is not shown. In the default brush
(one pixel), the brush's register-mark cursor allows for very fine and
accurate placement of single pixels in precise position with reference
to nearby pixels.

    The selected brush pattern paints in the currently active fill
pattern unless the INK option is active, in which case it paints in the
currently selected solid color. The brush function is the only
color-dependent function which does not indicate the selected color by
its cursor color, so you will have to toggle on the palette display if
you want to check the color selection. (Press Help while on a paint
screen.)

    There are 36 brushes shown in the brush selector boxes. A brush
pattern is selected by a left mouse click on the appropriate box. The
active brush pattern is highlighted. Clicking on a brush selector box
will switch the paint function into brush. The selected brush remains
highlighted at all times, even when brush is not the paint function.

    The user will note that the bottom row of boxes in the array of
brush patterns are empty. These six boxes are reserved for user-defined
brushes. When you first click on an empty user-defined brush box, a
brush pattern editor will be called up with which you can define a
brush. (See section on BRUSH EDITOR below.)

    User-defined brushes can utilize any or all the colors of the
active palette in a single brush pattern, that is, these brushes can be
multi-color brushes. User-defined brushes are painted to the screen in
the currently selected fill pattern unless the INK function is active,
in which case they are painted to the screen in the colors in which
they were originally defined. (They may also be painted in solid
colors, but the user must select MONO fill number 7 manually, without
engaging the INK option.)

    (Note: In low and medium resolution, the multi-colored user-defined
brush is not highlighted or printed in inverse to show that it has been
selected, as this would distort the colors. Instead, the brush selector
box's border is set to the selector color, that is, the color used for
pop-out menu frame cursors and around the borders of selected buttons.)

    I must caution you that user-defined brushes are unhappily slow
when used as brush shapes alone, that is, when the Ink function is off.
However, with Ink on (in the multi-color mode), they are the fastest of
all the brushes. The brushes in SEURAT do not have their positional
changes buffered. This means that if you move the mouse too rapidly,
the brush (like a real paint brush) will "skip" or fail to print at
aboslutely every intervening position between the beginning and end of
a very, very rapid mouse movement.

    Any selected block of any size may also be used as a brush. A
double-click of the left mouse button on the BLOCK button with BRUSH as
the active function will select the currently defined block as the
selected brush pattern. If no block is currently defined, an alert will
advise the user. When block is selected as the brush pattern the BLOCK
button will have a cross-hatched background and no brush pattern in the
brush selector boxes will be highlighted. The block-as-brush option can
be deselected by another double-click on the BLOCK button. The last
selected brush pattern in the brush selector boxes will be highlighted.

    A right mouse click or press of Escape returns you to the main
menu.

    BRUSH EDITOR: The brush editor functions in every regard like the
fill editor. The brush editor is called up whenever the user clicks on
one of the user-defined brush selector boxes when no brush has yet been
defined. The brush editor may also be called up by double-clicking on
one of the user-defined brush selector boxes when it displays an
already defined brush, thus allowing that brush to be altered or
replaced.

    The brush editor will construct multi-colored brushes using the
full palette allowed by the resolution the user is working in. These
brushes may be up to 16x16 pixels in size.

    Brushes are SAVEd and LOADed in a 256-byte format in the ASCII
value of the color numbers of the pixels, from the upper-left-hand
corner, proceeding in left-to-right and top-to-bottom.

    RAY:  Ray places a number of lines all drawn to a single center.
Place the cursor at the point where you wish the center of the ray
operation to be and click the left mouse button once to establish the
center. Move the cursor to another location and click the left mouse
button again. A line will be drawn to the center.

    Holding the left mouse button down as you move the mouse causes
continuous printing of rays to the center. A right mouse click indicates
that you are voiding the existing center location and wish to choose
another center with a further left mouse click.

    While the INK function is active, the lines drawn by ray will be in
solid colors, the color selected being indicated by the mouse color.
When the INK function is off, the lines drawn by ray will be in the
currently selected fill pattern, color or mono.

    Since a single right mouse click is used to allow the selection of
new center locations without a return to the main menu, an additional
right mouse click is required to exit the paint screen (or Escape).

    LINE:  Lines are always drawn in the currently selected solid
color (as indicated by the mouse color), never in the active fill
pattern. A single left mouse click indicates the location of the
starting point of the line to be drawn. An xor'ed line then follows the
cursor around while the line end-point is being chosen. A second left
mouse click fixes the line. A right mouse click voids the choice of
starting point and allows a new starting point to be chosen.

    A right mouse click or Escape returns you to the main menu. Two
right mouse clicks may be necessary if you have just voided a starting
point.

    POLYLINE:  Polyline draws connected lines in a closed figure
(polygon). A single left mouse click indicates the location of the
starting point of the polyline to be drawn. An xor'ed line then follows
the cursor around while the next line point is being chosen. A second
left mouse click draws the finished line to that intermediate point.
This process continues until the right mouse button is pressed, which
causes the next line segment to be drawn to the starting point, closing
the figure.

    If the Alternate key is held down while the starting point is
selected, the completed figure will be filled with the currently
selected fill pattern. The Alternate key need not be held down with
each successive left mouse click, only the starting point selection
click.

    A second right mouse click or Escape returns you to the main menu.

    BOX:  By box, SEURAT means an unfilled rectangle, or line figure. A
single left mouse click indicates the location of the upper-left-hand
point of the box to be drawn. An xor'ed box then follows the cursor
while the lower-right-hand corner of the box is being chosen. A second
left mouse click fixes the box in place. A right mouse click before the
box is fixed voids the operation and allows a new upper-left-hand
corner to be chosen.

    If the Alternate key is held down while the upper-left-hand corner
is being selected, the completed box generated will be what is called a
round-cornered box, although the actual figure is more like a clipped-
cornered box.

    Boxes, like lines, are always drawn in the currently selected solid
color, never the fill pattern. A right mouse click or Escape will
return you to the paint menu.

    SOLID: By solid, SEURAT means a filled rectangle, or solid prism.
The fill is always the currently active Fill Pattern. The resulting
figure has no single-color perimeter.

    A single left mouse click indicates the location of the
upper-left-hand point of the solid box to be drawn. An xor'ed box then
follows the cursor while the lower-right-hand corner of the solid is
selected. A second left mouse click fixes the solid in place. A right
mouse click before the solid is fixed voids the operation and allows a
new upper-left-hand corner to be chosen.

    If the Alternate key is held down while the upper-left-hand corner
is being selected, the solid generated will be a round-cornered filled
box.

    The solid is completely analogous to the box option in its
operation. A right mouse click or Escape will return you to the main
menu.

    CIRCLE:  Circle (and disc) are analogous to box (and solid) in
their operation. The figure drawn is actually an ellipse. A single left
mouse click indicates the location of the center point of the ellipse
to be drawn. An xor'ed ellipse surrounded by a dimension-box then
follows cursor movement. The vertical and horizontal distances of the
cursor position to the center determine the horizontal and vertical
axes of the ellipse. A second left mouse click fixes the ellipse in
place and removes the dimensioning box. A right mouse click before the
ellipse is fixed voids the operation and allows a new center point to
be chosen.

    If you wish a "true" circle, you must dimension it to what
is "true" by your own eye. However, two other useful options are
provided.

    Holding down Alternate while selecting the center point of the
circle or disc being drawn allows subsequent left mouse clicks to draw
circles or discs with the same center as the first. These subsequent
circles and discs also possess the same shape as the first circle or
disc drawn. This allows for the easy generation of concentric circles
and discs.

    Holding down Control while selecting the center point of the circle
or disc to be drawn allows subsequent left mouse clicks to draw circles
or discs which possess the same horizontal and vertical sizes as the
first drawn, but can be placed anywhere on the screen. This allows for
the easy multiplication of identical circles and discs.

    A right mouse click is the signal that the user wishes to draw
another set or type of circle or disc. Because of this use of the right
mouse click, you must use Escape to return to the main menu from
the circle (or disc) option.

    DISC: All procedures and options described above apply equally to
the drawing of discs. The disc is merely a filled circle. The fill is
the currently selected fill pattern. No solid color border is created
with the figure (no visible perimeter).

    As with the circle option, a right mouse click is the signal that
the user wishes to draw another set or type of disc. Because of this
use of the right mouse click, you must use Escape to return to the main
menu from the disc option.

    O-BOX AND O-CIRCLE:  O-Box and O-Circle are a box and circle that
is drawn in the currently selected color and which erases everything
underneath the box or circle as it is drawn. Unlike the conventional
box or circle, O-Boxes and O-Circles are drawn by depressing
and dragging the left mouse button.

    The results of drawing an O-Box or O-Circle in a write mode other
than overwrite are usually not intuitively obvious. Experiment with
some of these widely varying outcomes. With a little practice and some
mouse control, they can be quite striking.

    A right mouse click or Escape will return you to the main menu.

    AIRBRUSH:  The airbrush "sprays" pixels in a circular random
pattern weighted toward the center, much as an actual airbrush or spray
can would.

    The circular area in which the airbrush is active is set by the
user by depressing Control prior to holding down the left mouse button.
A variable diameter circle will appear which can be sized up or down by
mouse movement away from or toward the circle's center. The left mouse
button must be kept depressed during this operation.

    If the airbrush is not "sized" by the user, it has a default
diameter of six pixels. The airbrush is turned on by the left mouse
button and remains active while that key is depressed.

    The speed with which an area fills up with pixels depends solely on
the size of the active circular area selected while "sizing" the brush;
larger is slower overall. When the active circular area is very small
(about 3 pixels in diameter), the airbrush produces a very rapidly
drawn "fuzzy" line.

    The airbrush paints in the currently selected fill pattern unless
the INK function is on (highlighted), in which case it paints in the
selected solid color (as indicated by the cursor color). The airbrush
cursor is the normal arrow, but it is not printed to the screen during
the airbrush's operation.

    If Alternate is held down when the left mouse key is first
depressed, it does not "spray" pixels on the screen but rather "picks
up" a pixel at random and exchanges it for another pixel at a different
location, also selected at random. This randomization, or "smear
"effect, (also called stipple in some programs) can be used to blend
borders and blur too-sharp outlines. It produces a wide variety of
effects depending on the size of the area affected. The area size is
the same as the airbrush diameter (chosen with Control option).

    A right mouse click or Escape will return you to the main menu.

    TEXT:  The text option allows the placement of input text on the
paint screen. The cursor is a character cell approximately the size of
the largest character in the typestyle you have selected.

    To input text, enter it in the conventional fashion, through the
keyboard. The entered text is shown on the paint screen as a "floater"
(just as the selected block is shown). The backspace key deletes the
last entered character. Escape clears the line of type completely. All
other keypresses are appended to the text string being displayed.

    Text cannot be "pushed off" the screen by the text cursor. Its
placement must remain with the screen boundaries. (Note: Move the mouse
in a controlled fashion when nearing the edge of the screen with a text
"floater," as too rapid movement of the mouse at the edges of the
screen can cause the text "floater" to get "stuck" on the screen edge,
leaving a mess. Do not despair! The Insert-Undo erasure-and-update
system works during the text option, too.)

    Maneuver the text "floater" into position and affix it to the paint
screen with a left mouse click. A right mouse click (not Escape, which
clears the text string) returns you to the main menu.

    A single left mouse click on the TEXT button on the main menu will
select the text option. A double-click on this TEXT button calls up the
text dialog box. Type styles are selected by clicking on the type style
buttons in the upper portion of the text dialog box. Selection of any
type style except NORMAL turns off the NORMAL button. The other type
style attributes (italic, outline, bold, underlined, lightened) may
be selected in combination with each other, i.e., bold italic. Clicking
on NORMAL will clear all the other buttons.

    (The middle set of buttons, those for text rotation, are not
currently implemented. All text is printed to the screen in the
"normal" orientation.)

    The dot height selector allows values from 4 to 32. The currently
selected dot height is shown in the window between the two arrows.
Clicking on the left-hand arrow will reduce the dot height, and
clicking on the right-hand arrows will increase it. The numerical range
is modular, that is, trying to reduce the dot height from 4 to 3
results in 32, and trying to increase it from 32 to 33 results in 4.
The "canonical" sizes for text are 4, 6, 12, 24, 13, and 26 dots in
height; text of other heights may not have a pleasing appearance.

    The type style selected is displayed in the strip window below the
three sets of buttons. When the selected type color is the screen
background color, the box is filled with the writing color. Every
change made to the type attributes is reflected immediately in the type
style display. Below the type style display is a color palette for
choosing the text color; select with a single left mouse click.

    The text dialog box is exited by a right mouse click.

    The text dialog box can be accessed from the paint screen while
entering text. Simply press the up arrow cursor key and the text
dialog box will appear. All changes made to the type attributes in the
text dialog box are reflected in the "floater" type string when you
exit the text dialog box. Thus, all type attributes may be modified
before the user prints the text to the screen.

    The full 256-character ASCII set of the ST is available in SEURAT.
To access characters not assigned keys on the keyboard, simply press
the down arrow cursor key and a full ASCII set selector box will
appear. Select a character with a left mouse click. Up to nine
characters (at each call of the ASCII set selector box) may be appended
to the text string.

    Your selections are confirmed and the ASCII set selector box is
exited by a right mouse click.

    To exit the paint screen from the text option, you must use a right
mouse click (not Escape).

    PAINT SCREEN SELECTOR: Up to eight paint screens may be used in
SEURAT; the precise number available depends on the memory capacity of
your ST. Screens which are not available are shown with lightened
letters; these paint screen selector boxes will not respond to mouse
clicks.

    Each paint screen is a self-contained graphic entity with its own
color palette, which becomes active when that paint screen is selected.
Elements may be transferred between paint screens by means of the block
function. This is a simple matter when the two paint screens involved
have the same palette. In the case of differing palettes, the block may
be "pasted" to an unused paint screen having the same palette as the
destination paint screen and modified using the the color map routine
(see the section on color map below).  The active paint screen is
selected by a left mouse click on one of the paint screen selector boxes
"A" through "H." Each paint screen has its own palette which becomes
active when that paint screen is selected.

    Additionally, the selected paint screen may be changed while the
paint screen rather than the paint menu screen is displayed. The function
keys switch paint screens, with F1 corresponding to screen A, etc.
Calling a paint screen that doesn't exist (like F6 when you only have
five screens active) has no effect.  Switching paint screens without
returning to the paint menu screen forces an automatic update of the
paint screen you are switching from, just as if you had keyed Insert
before switching.  A double click on the active paint screen selector box
calls up a dialog box which allows the user to copy the currently
selected paint screen and its active palette into any other paint screen.
This function will totally erase any elements already contained in the
destination paint screen.  The screen copy dialog box (like the screen
assignment dialog box in the image load process) shows the filenames of
any images loaded into the eight paint screens. The destination paint
screen is chosen by a left mouse click on the appropriate screen label
button.  The user's action is reflected in the message line, the screen
status display which registers which screens are copies and which screens
were loaded from files, and by the highlighted button. Click the right
mouse to confirm and exit.  A double click on the active paint screen
selector box made while the Alt key is depressed calls up a dialog box
which allows the user to import any other paint screen's active palette
to the selected paint screen. This function will replace the selected
paint screen's palette with the palette of the source paint screen.  The
palette copy dialog box functions in an analogous manner to the screen
copy dialog box explained above.  Clicking on the last or highest paint
screen selector box while the Control key is depressed will cause that
paint screen to be voided and removed from further access for the purpose
of freeing up memory resources.  See the section on memory management for
a discussion of reducing the number of paint screens available, in order
to increase memory freespace.

    PALETTE DISPLAY:  The colors are arranged from the screen background
color (color 0) at the upper-left-hand color box to the writing color
(color 15, or 3, or 1, depending on the resolution) at the lower-
right-hand color box.

    A left mouse click will log in, or select, a color. The mouse will
turn the color currently selected and remain that color until another
color is selected.

    A double click on any of the color boxes in the palette display
will call up the palette editor dialog, in which palettes may be set,
modified, and SAVEd to and LOADed from the disk. See the section on the
palette editor (below).

    One of the most laborious aspects of any paint program is having to
flip back and forth to-and-from a menu screen in order to reselect
colors. SEURAT allows the user to make color selections without
flip-flop, directly from the paint screen.

    Simply press the Help key and the palette display will be printed to
the paint screen in the same location that it is to be found on the paint
menu screen. Select a color with a left mouse click. The mouse will
change color correspondingly. Then, a right mouse click unprints the
palette display. (The palette display must be unprinted before you can
proceed with any operation!)

    This process can be repeated as often as is required without leaving
the paint screen. When you return to the paint menu screen, the selected
color will be restored to the color that was selected when you entered
the paint screen.

    PALETTE EDITOR: The palette editor screen displays the full color
palette in a format arranged as the color palette is shown on the paint
Menu Screen and the Zoom Screen. In addition, it shows the color Number
and intensity values for each color.

    The color currently selected is indicated by the color of the palette
mouse (a palette with the abbreviation PAL beside it), except in the
screen background color, when the palette mouse has the writing color.
The action point of this mouse is in the center of the figure.

    The selected color number is shown in a box at the upper center of
the palette editor screen. Beside this box are the two color system
selector boxes. Color intensities may be shown in either the RGB system
native to the ST or in the Cyan-Magenta-Yellow system as used in color
photography. A left mouse click on the appropriate color system selector
box toggles the numerical display into that color system. Choice of color
system in no way affects the actual operation of the program; it is
merely a convenience for those more accustomed to the photographic frame
of reference.

    Individual color intensities may be altered by clicking on the
appropriate digits in the numerical display.

    Below the numerical display, the View button allows the user to see
the effect on the paint screen image of any changes made. The user may
return to the palette editor from the full-screen view by a right mouse
click or the Esc key. While the image is in the view mode, no mouse is
visible.

    Palettes may be SAVEd or LOADed by clicking on the buttons so
designated. Palette files have the file extension .PL1, .PL2, or PL3.
They are 32 bytes in length and are in the same form as used in the 3rd
through 34th bytes of the DEGAS picture format.

    The RESTORE button sets the palette back to whatever values it had
when the user entered the palette editor.

    The palette editor implements a color swap feature, similiar in its
usage to the auto color change feature of the fill editor. Double-
clicking on any color display box will swap that color in the palette
with the color currently selected. The selected color remains selected.
This feature is useful for swapping the screen background color with the
writing color, for example, as well as for easier rearrangement of the
palette.

    The palette editor must be exited with a right mouse click or by
keying Esc.

    While running SEURAT in monochrome, the palette editor is not
accessible, for obvious reasons, but several additional functions beyond
choosing black or white are available!

    In monochrome, double-clicking on the first color box of the palette
display (the screen background color) will cause it to reverse, thus
producing a paint screen image that is a "negative" or inverse of the
original image.

    Also in monochrome, double-clicking on the first color box (color 0)
of the palette display while you are holding down the Alt key will
reverse both the monochrome "color palette" and the image itself, thus
allowing a palette swap without altering the image. These two features
function only in high resolution (monochrome monitors).

     INK:  Clicking on the INK button toggles the fill selection to MONO
solid fill (number 7). INK is turned off by a) another left mouse click
on the INK button, b) chosing any other MONO fill pattern besides SOLID,
or c) clicking on the COLOR fill selector button. When INK is on, most
painting and drawing functions are performed in solid colors.
Additionally, when INK is on, the active user-defined brush (bottom row
of the brush selector boxes) are printed to the screen in the multi-color
mode. When INK is off these brushes are printed in the currently active
fill pattern. (See the section on brushes or the brush editor.) The INK
button is highlighted when the INK function is on.

     CLIP:  Clipping restricts all graphic functions to a predefined
rectangular area of the screen. Clipping is what GEM uses to limit
graphic output to windows, for example. SEURAT places control of clipping
in the user's hands. A double click on the CLIP button calls up the paint
screen with a thich crosshair mouse. Dragging with the left mouse key
held down will define an active area for graphic operations.

    After the clipped area has been defined, a click of the right mouse
key will return you to the paint menu. You will notice that the CLIP
button has not highlighted by setting the clipping coordinates. A single
click with the left mouse key on the CLIP button toggles the clip
function on and off. The CLIP button is highlighted when clip is active.

     If you attempt to turn clip on without setting  clipping coordinates
first, an alert box will inform you that no coordinates have been set.
Once the clipping coordinates are set, they are retained by SEURAT until
they are reset. This is true whether the clip function is on or off; that
is, clipping coordinates do not have to be set every time clipping is
turned on.

    The clipping coordinates may be displayed on the paint screen at any
time by pressing the "C" (or "c") key. The clipping rectangle will be
displayed until removed with a right mouse click. No operations are
possible until the clipping rectangle display is removed.

    AUTO: (See the section on ERASE AND UPDATE, below.)

    POP-OUT MENU:  Pop-out menus are called by clicking on the
appropriate menu button. Once they appear, the mouse must enter the menu
panel. A frame cursor follows the mouse from item to item. If the mouse
exits the menu panel without selecting an item the pop-out menu
disappears and no action is taken. If an item is selected by a left mouse
click, the menu panel is removed and the selection is acted upon.

    (Note: the frame cursor is normally printed in the frame or border
color, the second highest color number. Should this color be similar to
the screen background color and hard to see, it may be changed to the
writing color by pressing the Esc key. Another press of the Esc key
toggles back to the frame color. The frame cursor must be moved before it
will be printed in the new color.)

    The MENU button on the paint menu screen calls up a pop-out menu
containing the following options: Erase, which erases the paint screen;
Zoom, which allows individual pixels to be drawn; File, which calls up
the file function dialog box; block menu, a further pop-out menu which
accesses block manipulations;  Transforms,  a subroutine to perform
geometric transformations on entire paint screens; color map, a
subroutine to remap the color number assignments of pixels; and Quit,
the program exit.

    QUIT:  There are more reasons than neatness for exiting the program
by way of the Quit option. The program closing routine restores your ST
to whatever configuration was set when you entered the program:  drives,
Desktop palette, clipping coordinates, some poking around down into the
basement of the memory where pokes do strange things. Besides, there's no
other way out, except to (arghh!) reset or turn the machine off. (Don't
do it!)

    The File option calls up the file function dialog box, which offers
five disk routines. They are: a) Load an image file, b) Save an image
file, c) Delete any file, d) Set currently active disk drive, and e)
Format a disk (in the currently selected drive). Any number of file
operations may be carried out from the file function dialog box without
the user having to call it up again. The file function dialog box is
exited by a right mouse click.

    While operating out of the file function dialog box, the cursor is
configured like a floppy disk with the word "File" on it. The action
point of this mouse is in the center of the figure.

    LOAD IMAGE FILE: When loading an image file, the user will be
presented with the GEM file selector box. The file specification demands
an image file in the uncompressed DEGAS format with the file extension
.PI1, .PI2, or .PI3, depending on the resolution in which the program is
being run. In low resolution, SEURAT will load a NEOchrome image file
with the file extension .NEO; however, such files, once loaded, will be
only be saved in the DEGAS format.

    After the user has selected an image and its presence on the disk has
been verified, SEURAT with present the user with the image assignment
dialog box. The user must assign the image to be loaded to one of the
valid paint screens. A screen status table keeps track of which files
have been loaded into which paint screens.

    The paint screen selection may be changed any number of times before
confirming and exiting the image assignment dialog box with a right mouse
click. The message line and the screen status table are updated
continuously prior to exit. Assigning a loaded file to a paint screen
erases all preexisting contents of the paint screen. The user is not
querried or alerted to this possibility. When the image file is loaded to
a paint screen, that paint screen becomes the currently selected paint
screen.

    AUTO-LOAD OPTION: Often, work on a single image will extend over many
sessions with the program. To facilitate the multi-session work on a
single picture, I added the auto-load option. Any image file named
PICTURE.PI? (the ? indicates the appropriate boot resolution) will be
automatically loaded into paint screen A when SEURAT is loaded and run.
The PICTURE.PI? file must be on the root directory of the disk, not in a
folder.

    SAVE IMAGE FILE: The save image option always saves the currently
selected paint screen. The GEM file selector box called up will show as
default filename the filename the image was loaded under, if the image
was originally loaded into the currently selected paint screen.

    If the filename you have supplied does not already exist on the disk,
SEURAT will check the disk space available before attempting to write the
file to disk and you will be alerted if disk free space is less than the
required 32034 bytes. If the filename supplied by the user already exists
on the disk,  it will be overwritten without any further query of the
user.

    FILE DELETE:  Any file on the disk may be deleted by choosing it
with the GEM file selector box. The user will be asked to confirm the
deletion operation.

    SET DRIVE:  The drive selector dialog box shows the sixteen potential
drives supported by GEM. Unavailable drives are indicated in lightened
letters. Drives A and B always exist, even on a single drive system, as
logical drives. The user's selection is shown by the highlighted drive
box. No selection is validated until the Drive selector dialog box is
exited by clicking on "OK." Should a non-connected drive be selected by
the user, the choice is invalidated just as would occur had the user
clicked on "CANCEL."

    FORMAT DISK:  The disk format dialog box is virtually identical with
the GEM format dialog box and functions in the same way. The disk to be
formatted should not be inserted until SEURAT prompts you to do so.  The
format operation must take place in drive A. Any errors encountered  in
the formatting operation (or the hopeful absence thereof) are reported
after the operation is complete. The formatting operation may be repeated
as many times as desired without exiting the disk format dialog box.

    For  a  discussion  of the other  pop-out  menu  functions  (zoom,
transform and color map), see the relevent sections below.

    BLOCK MENU:  This option on the principal paint menu screen pop-out
menu calls up another pop-out menu, above the first, containing options
for the manipulation of blocks, as well options to LOAD and SAVE blocks
to disk.

    They are: a) Rotate block, b) Re-size block, c) Vertical Freeform
Distort, d) Vertical Arc Distort, e) Vertical Skew Distort, f) Vertical
Trapezoidial Distort, g) Horizontal Freeform Distort, h) Horizontal Arc
Distort, i) Horizontal Skew Distort, j) Horizontal Trapezoidial Distort,
k) Distort, l) Load block, and m) Save block.

    All block manipulation routines use the same mouse protocol. After
the user has indicated the the operation to be performed with the left
mouse button, a right mouse click causes the indicated operation to be
performed. When it is concluded, the user has three options: a left mouse
click voids the completed operation and allows for a repeat operation
on the same block to be performed; a right mouse click confirms the
already-completed operation and causes the modified block to become the
currently selected block, exiting the manipulation routine; and pressing
the Undo key voids the already-completed operation and exits the
manipulation routine with the original form of the block continuing to be
the currently selected block.

    All block manipulations are carried out on a single screen, which
must contain either the original block and the modified block or the
original block and certain modification indicators. This means that there
is a physical limitation upon the size of the block that can be modified
successfully.

    SEURAT does not calculate these size limitations; the rule here
is: if it works, great; if not, try again with a smaller block.

    ROTATE BLOCK:  The block is presented center-screen; above it is
rotation selector box. Rotation is calculated in the natural order of the
trigonometric functions, that is, with the 0° point directly to the right
of the center point and with rotation in the counter-clockwise direction.
Rotation in the clockwise direction is accounted negative rotation.

    Left mouse clicks on the directional arrows set the number of degrees
for the rotation. Holding down the left mouse key will cause the numbers
to advance rapidly. An xor'ed box shows the rotated orientation of the
block.  A right mouse click causes the operation to be performed. The
original block is placed in the upper-left-hand corner of the screen and
the rotated block is formed in the lower-right-hand corner of the screen.

    When the operation is complete, a right mouse click confirms the
new block, a left mouse click causes the operation to be repeated, and
Undo voids the operation without result.

    (Please note that the rotation options on the transform menu produce
vastly superior but slower results for rotations which are modular to 90
degrees.)

    RESIZE BLOCK:  The block is presented in the upper-left-hand corner
of the screen with an outline box showing the right and bottom edges of
the block. Grab the lower-right-hand corner of the block with the left
mouse button and drag it to the position it will occupy in the new block.
When the user releases the left mouse button, the operation will be
performed.  The resize option allows for both enlargement and reduction
of the block.

    If the Alt key is held down while the left mouse button is first
depressed, the resulting block will have the same proportions as the
original block.  If the Control key is held down while the left mouse
button is first depressed, the resulting block will be enlarged or
reduced to the same scale as the last completed resizing operation
performed. This allows a series of different blocks to be resized
identically. This feature is of use when a very large block is to be
segmented, resized, and recombined, also when portions of different paint
screens need to scaled identically.

    When the operation is complete, a right mouse click confirms the
new block, a left mouse click causes the operation to be repeated, and
Undo voids the operation without result.

    FREEFORM MANIPULATION: The following applies to both vertical and
horizontal freeform manipulations. The block is placed to one side of an
orientation line the height or width of the block. By dragging the left
mouse button to one side or the other of the orientation line, the
orientation line is deformed, pixel by pixel, to the path of the mouse.
Do not attempt to move the freeform shape of the orientation line nearer
to the block, but shape it centered on the original position of the
orientation line.

    A right mouse click will cause the block to be distorted to the
outline you have drawn. The freeform distort contour may be manipulated
indefinitely before commencing the operation. After the operation is
completed, it may be repeated by a left mouse click. Undo cancels the
operation and returns without result.

    ARC:  The following applies to both vertical and horizontal arc
manipulations. The block is placed to one side of a gate through which a
circular form squeezes back and forth as the user moves the cursor
without depressing any mouse buttons. The gate is the height or width of
the block.

    When the center of the circle is between the gate and the block, the
block will be distorted to the contour of that portion of the circle that
is on the side of the circle away from the block. In this case, it does
not matter if a portion of the circle passes through the block.

    When the center of the circle is on the side of the gate away from
the block, the block will be distorted to the contour of that portion of
the circle that is on the side of the circle nearest to the block. In
this case, do not allow a portion of the circle to pass through the
block, as the central portion of the new block will not be successfully
modified.

    In the case of a block very large in the dimension to be modified,
some or all of the gate may not be visible on the screen. The operation
will be performed successfully, however, whether the gate is visible or
not.

    Again, a right mouse click will cause the block to be distorted to
the arc you have positioned. The circle may be manipulated indefinitely
before commencing the operation. After the operation is completed, it may
be repeated by a left mouse click. Undo cancels the operation and returns
without result.

    SKEW:  The following applies to both vertical and horizontal arc
manipulations. The block is placed to one side of a gate through which a
skew-line is drawn. The skew-line may be pivoted about the center of the
gate as the user moves the cursor without depressing any mouse buttons.
The gate is the height or width of the block.

    A right mouse click will cause the block to be skewed to the
inclination of the skew-line. After the operation is completed, it may be
repeated by a left mouse click. Undo cancels the operation and returns
without result.

    TRAPEZOIDIAL DISTORT: A box is printed to the dimensions of the
block. The corners of this box may be moved by dragging on them with the
left mouse button depressed. The mouse cursor must approach to within
three pixels of the corner to "grab" it. In the vertical operation, only
the Y- coordinates of the corners may be altered; in the horizontal, only
the X- coordinates.

    A right mouse click will cause the block to be mapped to the
resulting trapezoidial figure. After the operation is completed, it may
be repeated to new parameters by a left mouse click. Undo cancels the
operation and returns without result.

    In the case of extreme distortions, it may happen that curvilinear
patterns of unfilled pixels are found in the distorted image. If the Alt
key is held down when the right mouse button is clicked, the operation is
performed with bigger "transfer pixels." However, this may result in an
increase in "chunkiness" elsewhere in the image.

    DISTORT: This is the all-purpose image manipulation routine.  Unlike
the trapezoidial distort, the four corners of the outline box may be
placed anywhere on the screen. (But do not allow them to intersect the
displayed block itself!) Distort scales up and down in size while
performing rotations and displacements. It is surprizingly fast (well, it
surprised me...) Oddly enough, it can perform a simple rotation faster
than the rotate option and with as great accuracy, but without using
trigonometric functions. Hmm..

    Usage is the same as the trapezoidial distorts (including the
fill-out option of the Alt key; see above).

    LOAD AND SAVE:  Blocks may be saved to disk and loaded from disk.  No
palette is saved with the block. The format of the block file is:  one
word (two bytes) giving the width of the block in pixels, one word (two
bytes) giving the height of the block, and a string of variable length
containing that portion of the screen as stored internally by GFA BASIC.

    GEM MENU ACCESS:  As you have almost certainly guessed by now, from
the descriptions of the various menus or from running the program itself,
SEURAT is not a GEM menu program with the traditional menu bar across the
top of the screen. However, this does not mean that you are denied access
to desk accessories!

    By double-clicking on the MENU button on the paint menu screen, you
can access a pseudo-desktop from which your desk acessories can be
called. This "desktop" will possess the color palette of the desktop from
which you booted SEURAT.

    In addition, under the "File" heading, the file function dialog box
can be called, although the "Load Image" and "Save Image" options are
unavailable through this "desktop." This does allow the user to change
the selected drive, format a disk, or delete any file.

    You can also call the GFA BASIC FILES function for a file directory
of the currently selected drive from the "File" heading on the menu bar.
It will show the presence of folders but not their contents.  (This
feature may result in a rapid scroll-over if there are more than 22 files
and folders present.)

    The option to return to the SEURAT paint menu screen is located just
under the "Desk" heading, where the credits or advert alert is usually
placed. SEURAT can be exited from this "desktop" by the "Quit SEURAT"
option.

    (Note: Calling the Control Panel accessory, or any other accessory
that changes or can change the color palette, will have no effect on
SEURAT's color palettes, which will be reinstated upon return to the
paint menu screen, voiding any changes made from this "desktop.")

    The  availability  of desk acessories  means,  among  other
possibilities, that you can load Print Drivers (Tom Hudson's INSTALL.ACC
in the first issue of START) or load any of a wide variety of alternate
fonts for use with the TEXT option (the public domain FONTRIX.ACC).
Although the Control Panel cannot be used to set the color palette, time
and date marking for files, keyboard delay and repeat rates, and so forth
can be set. The mouse double click speed cannot be set with the Control
Panel, as SEURAT has its own routines for that function. (It can be
adjusted, however; see the discussion of the Zoomscreen below.)

           OPERATIONS ON THE PAINT SCREENS


     ERASE AND UPDATE:  The paint screen can be erased entirely by
selecting the "Erase" option from the pop-up menu, presently the user
with a blank screen. This "Erase" is an irrevocable command and cannot be
undone.

     Controlled deletion of screen elements is left to the user's
management in SEURAT. Screen updating is performed by pressing the Insert
key while the paint screen is displayed. Insert triggers a screen
capture, and no element, once updated, can be undone. The user can, of
course, manually erase any element by painting it with a brush in the
background color, drawing a solid geometric form in the background
color over it, or otherwise tinkering with the pixels.

     Pressing the UNDO key while the paint screen is displayed erases all
operations performed on the paint screen since the last INSERT keypress.
An UNDO cannot be undone, except by performing the operations again.

     Updating of the paint screen is NOT performed automatically by
SEURAT (except by the AUTO function; see below). Therefore, it's a good
idea to acquire the habits of a) concluding every successful operation by
punching the Insert key (rather like keying Enter), or b) making frequent
Insert's, or c) keying Insert before attempting anything you think you
might mess up...

    The Undo-Insert system functions with all paint screen operations
except block, which has its own system.

    Block functions have their own item-by-item undo stack, which is
currently configured to be up to 100 items deep. This can be very handy
in a messy situation, but it can cause a mess, too. Attempting to place
100 2500-byte blocks, will create an Undo stack that uses a
quarter-megabyte of memory. This would almost certainly crash the program
(unless you're running it on a Mega, lucky you...)

    While the block undo stack persists and is always available while the
paint function is block, the two undo systems (block undo and Undo-
Insert) do not take notice of each other. No block operations are a
permanent part of the paint screen until an Insert is pressed. On the
other hand, the block undo can undo a block operation even though the
paint screen has been updated by Insert.

    Block undo removes blocks in the inverse order of their placement.
block undo is valid only for the paint screen where block placement has
been performed, whether the block was drawn from that screen or another.
Block undo is valid for that paint screen even though the user has
switched to another paint screen and back again, as long as no
intervening block placements are made on any other paint screen (since
the undo chomps down the stack in inverse order, destroying the saved
screen portions under the block placements but only restoring those on
the visible paint screen). Of course, it you can remember what order you
placed what blocks on which paint screen, you could unprint them all in
inverse order.

    The block stack works like this: the portion of a paint screen where
a block is to be placed is saved to the stack before block placement and
the stack pointer is incremented. The index of the paint screen is saved
with the block. When the user keys Undo, the stack pointer is decremented
and the screen portion is put back where the block was placed only if the
current paint screen is the same one where the block was originally
placed. If it is not the same paint screen, nothing is done to the paint
screen, but the screen portion is cleared from the block stack, i.e.,
wiped out.

    As you continue to place blocks on various paint screens, you will
notice a steady decline in the amount of free memory shown in the FRE
ledger line as the Undo stack grows. Once you are certain you will not
need to undo any block placements, the block undo stack can be cleared by
pressing the Backspace key.

    Note that the screen portion that replaces the block was saved when
the block was placed, and therefore any other paint operations performed
on the area of the block between the time the block was placed and the
time it is undone are not preserved (unless they were other block
placements).

     The AUTO option toggles on and off the execution of an automatic
paint screen update (just as if the user had keyed Insert). This paint
screen update is performed each time the user switches from the paint
screen to the paint menu screen or to any other paint screen. Activation
of the AUTO mode in no way interferes with the Undo-Insert or block undo
systems. The user may make additional updates by means of Insert at any
time. The AUTO button is highlighted when AUTO mode is active.

    MEMORY MANAGEMENT: At startup, the program creates screens until the
free memory that would be available to the running program falls below
184,000 bytes. This results in a variable memory workspace depending on
the machine configuration, number of active accessories, etc. Currently,
SEURAT running on a 1040ST with no desk accessories active provides 5
paint screens in low, 6 in medium and 7 in high resolution.

    Running the source code through the interpreter allows more screens
than the compiled program, a memory bonus that is more than compensated
for by the often-slower program operation. For the maximum memory
overhead, run SEURAT without any desk accessories active.

    SEURAT is not wasteful of memory resources. It contains its own
"garbage-collection" routines; storage variables are cleared after use,
dimensioned variables are erased when not in use and redimensioned again
when needed, etc.

    The 180,000 to 210,000 bytes that SEURAT allows for workspace is not
sufficient for all operations that can be performed. That is, depending
on the tasks you perform, it is possible for SEURAT to run out of memory!
I emphasize this fact because doing so will cause the program to crash in
flames, that is, terminate. But read on...

    For example, that is not enough memory workspace for the user to
select a block that is three-quarters of a screen in size and resize it
to a full screen. (Block manipulations are the the biggest memory
consumers.)

    What will you do? The answer is: SEURAT allows the user to monitor
and manage its memory requirements from within the running program.
Hmmm...

    Paint screens are provided for in memory when the program is loaded
and run. Each paint screen consumes 32000 bytes of memory. Paint screens
may be deleted from program access and their alloted memory turned back
to the program for other uses.

    To release memory, select the last accessible active screen selector
Box. That is, if "G" is the last paint screen selector box printed in a
normal (not lightened) letter, click on it to highlight (select) it.
Then, with the Control key depressed, double click on it.  The "G" box
will unhighlight, the box immediately above it (in this case, the "F"
box) will highlight and become the selected paint screen. The "G" box
will become unselectable (printed in a lightened letter), and the FRE
memory register will show an increase of 32000 bytes.

    This process may repeated any number of times, but SEURAT will not
allow you to remove the "A" paint screen! A paint screen that has been
made unselectable cannot be returned to active status during the same
run of the program. To regain the full screen capability, you must save
your work and rerun the program.

    So that the user does not have to keep watching the FRE register,
SEURAT provides a low memory warning: a burst of musical noise which
changes pitch with each repetition. This warning is sounded whenever free
memory falls below 64000 bytes.

             THE SEURAT ZOOMSCREEN

    To access the Zoomscreen from the paint menu screen, the user may
select the "Zoom" option from the pop-out menu or press the Clr/Home
key.

    THE SET WORK SCREEN:  If you have not yet entered the Zoomscreen
since the beginning of program operation, you will be presented with the
currently selected paint screen upon which to set the work area to be
enlarged. You'll know that it is the set work screen because the mouse,
while having its normal coloration, is upside-down; it is now a down
arrow instead of an up arrow.

    Set work screen operation is as follows: a left mouse click will
cause the appearance of an xor'ed box twenty pixels square. All SEURAT
work areas are square in configuration.

    This work area may be enlarged to fifty pixels square in low
resolution, a square one hundred by fifty pixels in medium resolution, or
one hundred pixels square in high resolution. To enlarge the original
square, depress the left mouse button and drag it downwards. The work
area may not be enlarged beyond the limits given above no matter how far
you drag the mouse.

    The range of zoom magnifications is 4 power to 10 power for low
resolution and 4 power to 20 power for high resolution. (In medium the
maximum magnification is 20 power along the x-axis and 10 power along the
y-axis.) The magnification selected will be the highest one consistent
with the maximum Zoomscreen size.

    This work area sizing operation may be repeated as many times as
needed. If so, previously drawn boxes will be erased when a new work area
is sized.

    The work area selector box may be positioned by pushing with the
right mouse key depressed. (The mouse is now upsidedown so it can't be
dragging any more, can it?) The work area can be positioned on any pixel
boundary.

    Both operations can be repeated as many times as needed by the user.
The number of each, left mouse and right mouse operations, need not be
equal. On the first use of the set work screen option at least one left
mouse and right mouse operation must be performed, but on subsequent
returns to set work screen the currently selected work area size can be
positioned by right mouse operations alone.

    When the work area has been selected, it will be zoomed when the user
presses the Esc key.

    THE ZOOMSCREEEN:  The maximum area allowed for zoom operations is a
square placed at the left-hand boundary of the screen, a maximum of 62.5%
of the screen area. The number of pixels per side of the work area is not
rationalized to integer multiples of the magnification, so the zoom area
may be somewhat smaller than the maximum. It will always be presented at
the highest magnification possible, however.

    The magnification factor of the zoom ratio is shown just above the
view window in medium and high resolution. In low resolution, it is
displayed just below the menu button where, in the other resolutions,
free memory will be displayed. (In low resolution, this display may be
selected for zoom ratio or free memory display by pressing the "F" or "Z"
keys.)

    The enlarged, or zoom, pixels are presented on the zoomscreen in a
discontinuous rather than continuous format. Their appearance is rather
like electronic graph paper (more about graph paper later). The zoom
pixels are positionally correct; they are merely one pixel less wide than
the magnification ratio. (This looks less confusing than it sounds.)

    A grid may be superimposed on the pixels. SEURAT calculates the
luminousity of the background color and makes an arbitrary decision about
whether or not to grid the first zoom of the first work area. Following
this, the grid may be toggled on and off by keying the F1 (function) key
(the grid toggle may also be selected from the pop-out menu; see below).
SEURAT performs all subsequent zooms in conformity to the last grid
toggle made by the user.

    ZOOMSCREEN VIEW WINDOW: The Zoomscreen view window displays an
upright rectangle which reveals a portion of the paint screen, that
portion which surrounds the work area. The work area itself is marked
with an xor'ed box in the view window.

    The Zoomscreen's view window functions like the paint menu screen's
view window, but with some additional functions. The X and Y coordinates
of the upper-left-hand corner of the work area are displayed in the lower
view window border. (There is also a "Z" box which we'll talk about in a
minute.)

    To select a new work area, the user does not have to return to the
set work screen. The new work area can be selected and zoomed from the
Zoomscreen through the view window.

    The area to become the selected work area can be scrolled up, down,
left and right one pixel at a time by clicking on the directional arrows
in the corner boxes of the view window border. (Note: The arrows refer to
the direction of movement of the window, not the movement of the portion
of the image shown.)

    The work area can also be shifted much more rapidly by dragging with
the left mouse button on the vertical or horizontal sliders seen in the
upper and left-hand portions of the view window's border. (Note: The
sliders alone are not able to reach the last few pixels at the edge of
the paint screen, but the arrows can shift the work area to the very
edge.  In general some "fine tuning" by the arrows may be necessary for
precision positioning, if required.)

    The work area will remain centered in the view window and the paint
screen will be scrolled until such time as the boundaries of the image
are approached. Then, the work area will shift in the view window until
the edge of the paint screen is reached.

    You will note that with the first movement of the work area selection
frame on the view window, that "Z" box that we mentioned just a moment
ago became highlighted. This indicates that the reselection process has
made a new zoom a program requirement. While the "Z" box is highlighted,
no Zoomscreen functions are active except those that relate to work area
selection through the view window.

    This allows you to rove over the entire paint screen if necessary
without zooming each area you pass over. When the work area selection
frame is positioned as desired, a left mouse click on the "Z" box will
zoom the newly selected work area.

    During work area selection, the work area may be resized if needed.
Pressing the up arrow key in the cursor block causes the work area
selection frame to be enlarged one pixel at a time until the maximum
permissible size is reached. The down arrow key reduces the size of the
work area selection frame one pixel at a time until the 20-by-20-pixel
minimum size is reached.

    The work area selection frame expands and contacts in alternate
directions on alternate keypresses in order to keep the work area
centered on the same portion of the image.

    Resizing the work area without any other movement commands will
also cause the "Z" box to highlight, requiring a new zoom.

    The "Z" box can clicked at any time to produce a zoom, whether
required by the program or not. It will not highlight in these cases.

    RETURNING TO THE SET WORK SCREEN:  If you prefer to return to the set
work screen to select a work area, simply press the Esc key.

    DRAWING ON THE ZOOMSCREEN: The user may draw on the Zoomscreen with
both left and right mouse buttons, each in a different color. The
selected left and right mouse colors are shown at the top of the right-
hand portion of the Zoomscreen. Beneath each mouse color box is the RGB
(or CMY,depending on the color system selected) of the two mouse buttons.

    The right and left mouse colors are selected by clicking with the
right or left mouse buttons on the desired color in the color palette
display just above the view window. While it is a convenience to have two
colors simultaneously available to the mouse buttons without reselecting
in low resolution, it is virtually a requirement in high resolution if
one is to achieve a reasonable pace of work.

    While the mouse is on the zoomed pixel portion of the Zoomscreen, the
mouse is displayed in the last color either selected or printed to the
Zoomscreen. When the mouse traverses off the zoomed pixels, it is changed
to a crosshair.

    SETTING THE MOUSE FACTORS: SEURAT utilizes two program variables, the
mouse click delay factor and the mouse flicker delay factor. They may be
set by pressing the F6 key, which will call up a mouse factor dialog box.
The factors may be set from 0 to 99 by clicking on the arrows.  Exit the
dialog by a right mouseclick.

    The mouse flicker delay factor is a variable in the zoomscreen mouse
drawing routine that greatly reduces mouse flicker when drawing on the
Zoomscreen. It does not produce a totally flickerless mouse, but a
properly adjusted factor can cut out most of the printing and unprinting
of the mouse that GEM wants to do. The magnitude of the mouse flicker
variable determines how long the program waits for the mouse to move
before printing the clicked zoomed pixel to the Zoomscreen.

    I have set the default values of 27 for mouse flicker and 50 for
mouse click by trial and error, but one value does not work equally well
when running SEURAT as SEURAT.PRG and when running the code through the
interpreter or the run-only program, and you may wish to tinker with it.
Different magnification ratios and your mousing habits will also affect
the result.

    Likewise, SEURAT uses its own routine to read double mouse clicks,
rather than relying on GEM. This routine is configurable to read almost
any number of mouse clicks. (GEM has a terrible time trying to read
triple clicks, much less 4, 5...)

    If your double-click doesn't always register with SEURAT, your
clicking may be too slow. Increasing the mouse click delay factor allows
more time for a doubleclick to be read. Conversely, really fast mousers
might get three clicks in during the allotted time, which would produce
no result. Reduce the mouse click factor, but DO NOT SET IT AT ZERO!

    The default values are set whenever the program is loaded; the
user's setting during the program are active only during the program
run
and are not preserved. The time unit of these factors is 1 = 1/200th
second.

    COLOR CHANGE FEATURE: If the Alt key is held down while the mouse
keys are also depressed, only pixels of a single color will be drawn to.
When the left mouse button is depressed with Alt, only pixels of the left
mouse color will be changed to the right mouse color. No other pixels
will be affected. Conversely, when the right mouse button is depressed
along with the Alt key, only pixels of the right mouse color will be
changed to the left mouse color.

    GRID COLOR:  When working in low resolution particularly, the color
of grid, when toggled, can greatly contribute to or detract from the
process of drawing on the Zoomscreen. Converting the grid color to the
color of one group of pixels solidifies those portions of the image and
throws the remaining pixel colors into greater contrast. The grid color
is selectable by the user.

    By pressing Shift and the F1 (function) key together, the mouse is
converted to the gridmouse. (The action point of this mouse is in the
center.) Click with the left mouse on the desired color from the color
palette display. Click with the right mouse to confirm your choice. A
grid of the selected color will be activated if the grid toggle is on. If
not, when it is toggled on, the grid will be displayed in the newly
selected color.

    Grid color selection may also be accomplished from the pop-out
menu (see below).

    COLOR FLOOD:  The work area may be flooded with a single solid color
by double clicking on the desired color in the color palette display. The
work area may also be flooded with a single solid color by selecting the
desired color from the color palette display with the left mouse button
and then depressing the F4 (function) key.

    ERASURE AND UPDATE:  The Insert and Undo key system functions
on the Zoomscreen in the same manner as it did on the paint screen.

    ABSOLUTE X-Y COORDINATES:  The absolute X-Y coordinates of any zoomed
pixel are shown with this function. By "absolute," SEURAT means the X and
Y coordinates of the source pixel in the paint screen, not the position
of the zoomed pixel on the Zoomscreen.

    To display the absolute coordinates, depress the F2 (function) key or
select the appropriate option from the pop-out menu (see below). The
mouse is converted to the brush crosshair cursor and the absolute
coordinates of the zoomed pixel the cursor is positioned on are shown in
the lower border of the view window where the coordinates of the upper-
left-hand corner of the work area were formerly displayed.

    To cancel the function and restore the work area coordinate display,
click with the right mouse key. No other operations are possible while
displaying absolute coordinates.

    VIEWING THE PAINT SCREEN:  A full-screen view of the paint screen may
be obtained by clicking the right mouse key while the mouse is inside the
borders of the view window. The user may also opt to view by depressing
the F7 (function) key. To return to the Zoomscreen, key Esc or click the
right mouse key. While the image is in the view mode, no mouse is
visible.

    RETURNING TO THE PAINT MENU:  Return to the paint menu screen by
pressing Clr/Home, or by selecting Paint from the pop-out menu.

    ZOOMSCREEN POP-OUT MENU: The menu button is located in the upper-
right-hand corner of the Zoomscreen. When the mouse enters the button, it
converted to the normal GEM mouse. Click on the menu to call the pop-out
menu. This menu functions identically with the pop-out menus on the paint
menu screen. The Zoomscreen menu contains most of the options listed
above.

    Additionally, it allows the user to erase the entire paint screen
from within the Zoomscreen, to access the file function dialog box, to
return to the paint menu screen, to access the palette editor, the
transform and color map routines, to switch paint screens, and to quit.

    Originally, the Zoomscreen was the main procedure of SEURAT and the
paint menu was an off-shoot. I have turned things around somewhat to
conform to user's expectations of how a paint programs are usually
structured, but in practice, the user may operate as quickly and
efficiently out of the Zoomscreen as "home base" as out of the paint
menu. I do.

    When the user changes the paint screen through the Zoomscreen (either
by loading in a new image by means of the file function dialog or by
calling the screen selection dialog), the new image is substituted for
the existing one without exiting the Zoomscreen. That is, the new work
area, with the same size and screen coordinates as the previously
selected one, is displayed in the view window with its surrounding view
area and zoomed.

    When returning to the Zoomscreen from the paint menu or from
transforms or color map, the previously selected work area is updated
with any changes that have been made since the user left the Zoomscreen.
If the selected paint screen has been switched to another paint screen
than the one last selected while the user was in the Zoomscreen, the
newly selected paint screen is zoomed instead.

    The  ability to switch paint screens without altering any parameters
of the Zoomscreen allows the user to directly  compare corresponding
areas of differing versions of the same image stored in different paint
screens, for example.

    ALTERNATE ZOOM MODE:  The zoomed pixels may be displayed in two
modes: one, as explained above, and the alternative mode, in which the
zoomed pixels are printed to the screen in continuous contact with each
other.

    Drawn objects may be loosely and not exclusively catagorized along an
informal spectrum from geometric to naturalistic. Many of the color fills
are examples of geometrically drawn graphic objects, and a digitalized
photograph which consists of intensity contours is a good example of a
naturalistic object.

    Naturalistically drawn objects are much more easily modified when the
pixels are distinct and independent entities, as in SEURAT's normal zoom
mode. Geometric objects are more impressive when the zoomed pixels are
merged seamlessly.

    If the user holds down the Alt key while clicking on the "Z" box
on the Zoomscreen view window to initiate a zoom, the resulting zoom
will
be performed in the merged-pixel mode. The grid toggle will be turned
off,
and no grid will be printed.

    The merged-pixel mode will remain in effect until the next time the
"Z" box is clicked. That is, if the user leaves the Zoomscreen in the
merged-pixel mode, and later returns to Zoomscreen, the zoom will be
performed in the merged-pixel mode. However, this alternative zoom mode
must be set again (by holding down the Alt key) whenever the "Z" box is
to be clicked again.

    The user may switch between the two zoom modes at any time by
clicking on the "Z" box (with or without the Alt key), whether or not a
zoom is required by the program. (Also, a merged-pixel display can be
converted to a normal-mode display, without changing the mode, by merely
toggling the F1 key to cut the pixels.)

    ALTERNATE KEYSTROKE COMMANDS:  Alternate keystroke commands are
available for all of the functions listed on the pop-out menu. The
following full list of keystroke commands are valid for use on the
Zoomscreen:

    Esc = Set work screen
    Insert = Update restore
    Undo = Restore work area
    Clr/Home = Paint menu screen
    Up Arrow = Enlarge work area
    Down Arrow = Shrink work area
    f1 = Grid toggle on/off
    f2 = Abs. X-Y coordinates
    f3 = 20x20 mode toggle
    f4 = Flood with left mouse color
    f5 = Set color palette
    f6 = Set mouse factors for flicker and double click
    f7 = View image
    f9 = File functions
    Shift-f1 = Set grid color
    Shift-f4 = Screen transforms
    Shift-f5 = Erase screen
    Shift-f8 = Select screen
    Shift-f9 = Color map

    THE TWENTY-TWENTY MODE: When the user toggles the Zoomscreen into the
20x20 mode, the work area is reselected to the minimum size, 20 by 20
pixels. Moreover, this work area is placed on the nearest pixel boundary
that is modular with respect to its size, that is, with X and Y
coordinates of 0,20,40,60,80... and so forth.

    While in the 20x20 mode, the directional arrows shift the work area
by units of 20 in all directions, rather than by one pixel at a time.
The coordinate display in the lower border of the view window is
expressed in horizontal and vertical modules of 20 pixels (H=3 V=2 is the
same as X=20 Y=10). The up arrow and down arrow cursor keys will not
resize the work area.

    If the user returns to the set work screen in the 20x20 mode, the
cursor is a 20/20 mouse, the work area selection box moves only in
modular jumps of 20-pixel intervals aligned on horz. and vert. modular
boundaries, etc.

    When the 20x20 mode is canceled by reselecting the toggle from the
menu or keying F3 again, the work area remains the minimum 20-pixel size,
but may be resized, moved, and altered from the view window or the set
work screen as before. The work area coordinate display returns to X and
Y coordinates, the arrows move the work area one pixel at a time, etc.

    You may have noticed that in the normal zoom mode there are some
spaced-out grid lines that are printed in color O, whatever the grid
color may be. They represent the X and Y coordinates of the paint screen
that are modular to 20 pixels in height and width. An area enclosed by
such grid lines is an area which can be selected as a whole in the 20x20
mode.

    The 20x20 mode, used in conjunction with preplotted graph paper
drawings, is the best method to take fullest advantage of the remarkable
resolution offered by the Atari SM124 monochrome monitor.  In any
resolution, it offers the most precise method of transfering preplanned
graphics to the screen.

              SCREEN TRANSFORMS

    The screen transform routines perform a variety of geometric
transformations of entire paint screens.

    By geometric transformations, SEURAT refers to those manipulations of
the image that can be performed with completely mutual one-to-one
correspondance between the original and transformed pixel locations.
That is, one and only one destination for each pixel to be moved, and one
and only one pixel for each destination to which pixels are to be moved.

    Technically, this requirement is also true for some of the block
manipulations such as skew, arc, and freeform. However, for a
manipulation such as rotation or resize, such is not the case. An
attempted one-to-one rotation procedure will leave the finished image
full of "holes" where no pixel was placed and overwrites at locations
where more than one pixel was placed, due to rounding and floating point
errors, inaccuracies in the trancendential functions, and so on.

    These screen transformations are designed to commit no (or little)
damage to the original pixels and their relationship with each other
(whatever their orientation). (Precision requires every pixel it can
get!)

    They are performed on whole screens (or as much of a screen as
possible), but they may be utilized as a class of block manipulations by
performing them on a copy of a paint screen and transfering portions of
the "transformed" image back to the original paint screen as blocks.  Or,
a block may be "pasted" to an unused paint screen and be brought to
transforms to be manipulated.

    The transforms may be used to manipulate or reorient whole screens
in a quick and effective manner. These routines also include a set of
symmetry functions that will create singly or multiply mirrored images.

    The functions and features of the transform routines are as
follows:

    THE TRANSFORMS MENU:  The transforms menu is a drop-down menu which
is toggled on and off by the program as required and by the user as
desired. A right mouse key click prints and unprints the menu. Moving the
small crosshair cursor to the heading of either menu panel causes it to
drop down. Unlike a conventional GEM menu, if the mouse leaves the menu
panel without selecting, the menu panel will pop back up out of sight.

    A frame cursor follows the mouse cursor from item to item. An item is
selected by a left mouse click. One menu item, the chain feature (see
below), is toggled on and off by left mouse clicks. When CHAIN is
highlighted, it is on.

    CHAIN: When chain is active, each transformation the user selects is
performed on the outcome of the previous operation, if any. When chain is
off, each operation is performed on the original screen with which the
user entered the transforms routine. To abort a series of chained
operations and begin a new sequence of chained operations, simply toggle
chain off and on again.

    Chain functions somewhat differently when used with the two
rotation operations. Consult the appropriate section below.

    TRANSFORMS CURSOR: Some transform operations utilize an additional
cursor, the full-screen crosshair. They are: the four mirror operations
and the two rotations. The function of this cursor is explained in each
relevant section below.

    FLIP: Reverses the screen from left to right, a "mirror" image in
the sense that it presents the way the original screen would look if
viewed in a mirror.

    INVERT:  Turns the screen upside-down. (Note: The combination, or
chaining, of a flip and an invert constitutes a 180-degree rotation.)

    ROTATION 90° CLOCKWISE: This routine acts only on user-selected
screen portions that constitute a square. The remainder of the image is
erased before the operation is performed. The screen returned after the
operation contains only the rotated screen portion. In that sense, the
procedure is very much like the routines included on the block menu.  But
unlike the rotation algorithm used in the block rotation, this procedure
meets the criteria for a truly geometric operation.

    However, the pixels on the ST monitors are approximately 10% higher
than they are wide, thus distorting the final appearance of an uniform
transformation.  Therefore, an adjustment for pixel aspect ratio is
included in the routine as the default condition, improving the result
considerably for naturalistically drawn objects.

    However, this same adjustment distorts the regularity of geometric
graphic objects. By holding down the Alt key while clicking on this
option on the menu,  the operation will be performed without any
compensation for pixel aspect ratio.

    The full-screen crosshair cursor that appears after the user clicks
on this option from the menu allows the selection of a square screen
portion of any size up to the full height of the screen. Place the cursor
on the upper-left-hand corner of the area to be selected and, depressing
the left mouse key and holding it down, drag the box that will be printed
to the screen to the size desired. When the left mouse key is released
the operation will be performed.

    Since the rotation operation discards the portion of the screen not
involved in the rotation, inclusion of a rotation in a sequence of
chained operations necessarily voids that portion of the previous results
that lies outside the selected screen area. Commencing a chain of
operations with the rotation of a large screen area minimizes the area
loss, but the user will find that the transform operations are quite as
useful on small screen areas as on entire screens, if not more so.

    This operation is somewhat slow if it is performed on the largest
possible area, but it's not irksome when performed on small or
moderate-sized areas. Be patient; remember, this program's first criteria
is accuracy and precision; speed comes second... OK, OK, a close second.
Besides, I kind of like watching the square twirl around inside itself.

    ROTATION 90° ANTI-CLOCKWISE: This routine is absolutely identical
with clockwise rotation in every regard except for the direction of the
process. All commands and options are the same.

    (180-degree rotations can be accomplished by chaining a flip and
an invert operation.)

    MIRROR  OPERATIONS:  The four mirror transforms produce  a
"reflection" of one screen area in another area of the screen. One may
produce a screen in which the left-hand-side mirrors the portion of the
image in the right-hand-side, or vice versa. Also, the top portion of a
screen may be mirrored in the bottom, or vice versa.

    A single-line cursor is displayed, either a vertical or a horizontal
line depending on the intersection of the reflection to be performed. The
cursor should be placed where this intersection is desired and the left
mouse clicked to perform the operation.

    If the user depresses the Esc key instead (regardless of the cursor
placement), the operation will be performed with the horizontal or
vertical mid-point of the screen as the axis of relection.

    SCROLLING OPERATIONS:  These operations scroll the entire screen
left, right, up or down, as selected by pressing one of the four cursor
arrow keys. The screen is scrolled in the direction of the key pressed by
the current scroll set factor (default is one pixel). The scroll
functions are terminated by a right mouse click, which restores the menu.

    SET SCROLL STEP:  The vertical scroll operations function very
rapidly, the horizontal scrolls less so. This option allows the number of
pixels by which the screen is shifted to be increased from the default of
one pixel at a time. The maximum value is eight pixels.

    EXIT:  The transform routine may be exited returning the current
transformed screen ("New Image") or all operations performed may be
aborted ("Old Image"), in which the original screen is returned
unaltered.

                COLOR MAP

    The color map routine allows pixels of a given color number to be
transformed into pixels of another color number. Up to the full number of
colors available in a given resolution may be modified in a single pass.

    COLOR MAP DIALOG BOX: The color map dialog box displays two rows of
color boxes containing each color of the palette connected in a
one-to-one correspondence. (The color numbers are displayed in
hexadecimal because of space restrictions.) When the user clicks with the
left mouse key on any box in the upper, or source, row, the connecting
bar will be unprinted.

    By clicking on any color box in the lower, or destination, row, the
connecting bar will be redrawn to that box to show the color change
sequence to be performed. The color box of the source row is redrawn in
the destination color selected.

    This procedure may be repeated for any or all colors in the current
palette before commencing the operation.

    The reset button cancels all selections and redraws the color map
dialog box.

    Clicking on "Select Area" displays the paint screen and the full-
screen crosshair cursor. Dragging with the left mouse key selects the
area to be remapped. The operation is performed when the left mouse key
is released.

    Clicking on the Whole Screen option causes the remapping to be
performed on the entire paint screen.

    When the operation is complete the user is presented with an alert
offering three options: to continue with another color-mapping operation
("Again"), to return the current result ("New"), or to abort the result
and exit the procedure ("Old").

    Choosing the "Again" option preserves previously selected color
mappings in force unless the reset button is clicked. Use with "Select
Area" only, as "Whole Screen" would produce no further result.


               DISK INFORMATION

    For SEURAT to run, it must have the file SEURAT.DAT, which is
normally present on the root directory of the disk from which the program
is loaded. If the SEURAT.DAT is not present, an alert will give the user
the option of changing disks and retrying to access the data file. The
other option is to abort the program and return to the Desktop.

    PRINTING IMAGES: There is no specific hardcopy routine in SEURAT.
Simply go to a view of the image which has no mouse on screen (the view
modes) and press the Alt and Help keys together. The quality of the
print-out will depend on the print driver you have installed. If your
printer is not turned on or is not online, the program will hang up for
30 to 40 seconds, then resume. Don't panic and turn the ST off, OK?

    IMAGE CONVERSION AND COMPRESSION: SEURAT will not load compressed
images, nor compress images for storage, nor will it convert from one
picture format to another nor from one resolution to another (I had to
leave out something!).

    There are a number of very good conversion and compression utilities
in the public domain. Use them.

               ERROR MESSAGES

    SEURAT.PRG will terminate upon error, however, a GFA BASIC error
message will be displayed first. It is almost certain to be "Not Enough
Memory!"

              PROGRAMMING NOTES

    SEURAT is programmed in GFA BASIC, a product of GFA Systemtechnik,
distributed in the U.S.A. by MichTron. I'd like to add: Thanks!  A BASIC
in which one can write a program of this length and complexity without
horrendous results (even if I did fall asleep nights with rows of bombs
dancing across the under-surface of my eyelids) is deserving of high
praise indeed.

    RUNNING SEURAT UNDER THE GFA BASIC INTERPRETER: At the very
beginning of the program, it is useful to to insert a line ("On Break
Gosub End") immediately after the On Error statement (2nd line). At the
very end of the program, change the last line in the Procedure End
subroutine from "System" to "Edit."

                ODDS'N'ENDS

    SEURAT is dedicated to Georges Pierre Seurat (1859-1891), the
Father of the Pixel. May their numbers increase!

    QUESTIONS AND ANSWERS:  Are there any bugs in SEURAT? Yes, two
Busy Bees and a Lady Bug, in the Fills.

    MORE QUESTIONS AND ANSWERS:  What are those funny looking red
bombs in the default color fill? Don't ask...

    LAST MINUTE HINTS:  Don't click on paint functions "on the fly," that
is, while rapidly scooting the mouse around (I'm guilty of this a lot
myself). The paint menu screen is one long, long, long loop, and once in
a while the mouse may be read after you've moved it out of the button
box, thus selecting and highlighing the wrong function.

    Occasionally, you may also find that an extra right mouse click (or
two or three or...) is required when returning from a complex series of
operations, in order to switch from the paint menu screen to paint
screen.  This is caused by recursive nesting, and you have to back up out
of the loops.

      ------------------------------------

    GEM is a Trademark of Digital Research, Inc.
    ATARI 1040ST, 520ST and Neochrome are Trademarks of
    the Atari Corp.
    DEGAS is a Trademark of Electronic Arts, Inc.
    GFA BASIC is a Trademark of GFA Systemtechnik.
    SEURAT is a Trademark of SKWare One, Inc.