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pixFX Documentation Version 2.1 December 1990 Copyright (C) 1990 Golden Hind International All rights reserved Introduction ------------ pixFX is an IBM PC program for displaying GIF images from 2 to 256 colors on an SVGA 640 x 480 x 256, VGA, or EGA display system. pixFX combines ease of operation with many new features previously not available in GIF viewers. These features include: - pictures are automatically scaled to full screen size and displayed with the correct aspect ratio. - pictures using more than 16 colors such as scanned photographs are displayed with automatic contrast and brightness control, and automatically color-reduced if necessary. - many special effects are available, including photographic and digital image processing operations. - the special 360 x 480 x 256 color mode is supported on IBM compatible VGA displays. Because of the automatic scaling, VGA users can see practically all GIF images in near Super VGA quality. pixFX is both educational and fun! Installation ------------ To install pixFX, simply execute the archived program to extract the PIXFX.EXE module. When executed pixFX will automatically detect which video hardware is available and use the mode which gives the best possible resolution. In some cases pixFX may not correctly recognize the video hardware, in which case the video mode may be overridden by setting the PIXFX environment variable. See the video modes section of this document for details. Operation --------- pixFX may be operated either from the DOS command line, or interactively. The format of the commands is the same in both cases. DOS command line: To display a GIF picture, issue the command: pixfx [options] GIFfilename Example: pixfx -b150 -m -v vga256 picture.gif Interactive: Invoke the program pixFX without any parameters. A command line is displayed for entering options. This command line may be edited with the left and right arrow keys, the Delete, Backspace, Home, and End keys. The GIF files in the current directory are displayed, and the currently selected file is highlighted. If no file name is entered on the command line, the currently selected file is used. To select a particular file from the current directory, use the up and down arrows. The Tab and Shift-Tab keys may be used to move between columns of the displayed directory. The Page Up and Page Down keys are used to move between different pages of the displayed directory if it does not fit on one page. To switch to any other directory or drive, simply type its name by itself on the command line, e.g. D:\GRAPH Options ------- Options are provided for further control the operation of pixFX, and to product special effects. Each option is a minus sign followed by a letter with no intervening space. Some options require a numeric parameter, as shown in the list below. The format of the options list follows UNIX (tm) conventions - case is significant! Options may be mixed in any combination. pixFX can make sense out of unusual values of some parameters - e.g. a negative value or a very large value for contrast. The possibilities are endless! Flags ----- -h halftone Halftoning is available for both monochrome (B&W) and color pictures. B&W halftoning uses only black and white to simulate all shades of gray. Color haftoning uses 8 colors (black, white, red, blue, green, cyan, magenta, and yellow) to simulate all colors in all shades. (Pictures that are to be printed are normally halftoned because most printers can only place ink at full density on paper. There are two basic methods of halftoning: the one most widely used in the printing industry uses dots of variable size; the other uses fixed size dots. The second method is used in most printers attached to computers, and is becoming more popular.) pixFX V2.1 uses the well-known Bayer dithering matrices for halftoning. There are several other halftoning methods available based on a concept known as error diffusion. Because of the popularity of 300 dpi laser printers there is a growing need for high quality computer algorithms for halftoning. Golden Hind International is actively researching this technology. -i information The dimensions of the GIF image and the number of colors are displayed on the status line. -m monochrome Colors in the picture are converted into shades of gray, similar to B&W TV or a B&W photograph. pixFX uses the television standard for monochrome conversion, the NTSC Y luminance component of a color picture. -n negative Colors and shades of gray are inverted, giving the appearance of a photographic negative. (Color photographic negatives include an orange mask, so they don't appear as true negatives.) -s solarize When photographic film is highly overexposed, as for example by pointing at the sun, areas of high light intensity may end up dark. This characteristic is now used intentionally as a special effect known as "solarization". (For pixFX to solarize a picture, the contrast must be set at a value considerably higher than 100%. Because most pictures with more than 16 colors are displayed with an automatic contrast setting considerably greater than 100%, it is usually not necessary to specify a contrast setting.) -Y false color The colors of the picture are intentionally changed: green becomes red, blue becomes green, and red becomes blue. False color is an image processing operation which can be used to bring out hidden aspects of a picture because the psychological link between objects and their normal colors is broken. Infrared pictures are one form of false color. -Z pseudo color Different shades of gray are displayed instead as different colors. Pseudo color can be used to bring out features in monochrome pictures that might otherwise be missed. (Because pseudo color only takes a monochrome input, pixFX will convert a color picture to monochrome first.) Parameters ---------- All these options take a numeric value following the option, separated by a space. Most options take an integer value. This options which require a real value are specifically identified in the following list. -a picture aspect ratio The picture aspect ratio is its width divided by its height. pixFX can usually determine a picture's aspect ratio, but sometimes it may be necessary to override this decision. For reference, the aspect ratio of the screen on a personal computer is 4/3 or 1.333, the same as TV. A different aspect ratio of 6/5 is common on workstations. (Note that the aspect ratio of a picture is NOT always the number of pixel columns divided by the number of pixel rows.) If you want to test that your monitor's vertical height and horizontal widths are adjusted to their correct values, display a picture with the aspect ratio forced to 1.000 and measure the picture on the screen. -b brightness This option sets the overall brightness of the picture. The parameter is expressed in percent, with the default being 100% for 2-16 color pictures. For 32-256 color pictures, the default brightness is set automatically, depending on the overall brightness of the original image. Automatic brightness adjustment is turned off for any image whose filename is of the form PIXFX*.GIF. -c contrast This option sets the overall contrast of the picture. The parameter is expressed in percent. The default for 2-16 color pictures is 100%, while the default for 32-256 color pictures is set automatically, depending on the overall contrast of the original image. For many images, the default contrast setting will be in the range 150-175%. Automatic contrast adjustment is turned off for any image whose filename is of the form PIXFX*.GIF. -g gamma Most cameras and monitors do not exhibit a linear response between light intensity and film density or electrical signal levels. This non-linearity is expressed as gamma, the exponent of the algebraic power relationship between light intensity and film density or electrical signal. Thus: film density = a * (light intensity) exp gamma The gamma option in pixFX applies an additional correction. The default is 1.0 - a value less than 1.0 reduces contrast, while a value greater than 1.0 increases contrast. Gamma correction is carried out by pixFX before any other options. -o ordered dither Each pixel has some ordered dither added to it. The dither value is based on the 4 x 4 Bayer dithering matrix. The maximum amount of dither is plus or minus 1/2 the parameter value (the R, G, and B component of each pixel is encoded in the range 0 to 255). Ordered dithering can be used to smooth transitions in images such as occurs in sky backgrounds and flesh tones. The dithering is only applied to mid-range values. See also the -r parameter. -p posterize Posterizing is a special effect where a limited range of colors or shades of gray are used to display a picture. The parameter specifies the number of levels to be used - 2, 3 or 4. -r random dither Each pixel has some pseudorandom noise added to it. (The pseudo- random noise on pixFX is "blue" noise, which has had the low frequency component removed for better appearance.) The parameter specifies the total range over which an individual pixel can vary, based on black being 0 and white 255. Random dithering can be used to smooth out transitions in images and also to generate special effects. (Try -p 2 -m -r 128.) The dithering is only applied to midrange values. See also the -o parameter. Random and ordered dithered can be used in combination if desired. -v video mode See the separate section on video modes. -x x offset This parameter is the x location in the picture corresponding to the center of the screen. Allowable values are -100 to +100, with the default being 0. The main use of this option is for pictures scaled at more than 100%. -y y offset This parameter is the y location in the picture corresponding to the center of the screen. Allowable values are -100 to +100, with the default being 0. As for the x offset option, the main use of this option is for pictures scaled at more than 100%. -z scale factor At the default value of 100% pixFX automatically scales each picture so that it fills as much of the screen as possible, while still maintaining the correct aspect ratio. Pictures may also be displayed at more or less than full size by setting the scale factor option. The scale factor option is intended to be used in conjunction with the x offset and y offset options. For example, the options: -x 100 -y 100 -z 300 will magnify the picture 3 times, and place the top right corner of the picture in the exact center of the screen. -A hue This parameter corresponds to the tint control on a color TV. Allowable values are from -100 to +100, with the default being 0. The hue option works by adjusting the equivalent NTSC I and Q color TV signal components. -B saturation This parameter corresponds to the color control on a color TV. The default is 100%. Setting saturation to 0 will generate a monochrome picture. Similar to the hue option, the saturation option works by adjusting the equivalent NTSC I and Q color TV signal components. The options for brightness and contrast of individual colors are grouped together below. The default for these values is 100%. Note that these values multiply the overall picture brightness and contrast values set by the -b and -c parameters. -C red brightness -D red contrast -E green brightness -F green contrast -G blue brightness -H blue contrast -I yellow brightness -J yellow contrast -K magenta brightness -L magenta contrast -M cyan brightness -N cyan contrast -X pixelation The picture is subdivided into squares, with each square displaying the average color of the original picture. (The picture appears as though it is being displayed with very coarse pixels, hence the name pixelation.) The parameter is the number of squares to be used along the width of the picture. (Values of 20 to 40 give good results.) Note that this special effect is generated AFTER the original picture has been displayed. Video Modes ----------- There are 3 ways of specifying which video mode pixFX will use to display images: If no mode is specified, pixFX will automatically detect the available hardware and choose the highest mode available - SVGA, VGA or EGA. (Because of the automatic scaling performed by pixFX, the user normally does NOT need to specify the video mode needed to display any particular image.) The default video mode may be specified by setting the PIXFX environment variable, e.g. SET PIXFX=VGA256X The video mode may be set for an individual image on the command line by using the -v option, e.g. -v tseng (Tseng SuperVGA adapter in 640 x 480 x 256 mode.) The video modes supported by pixFX are: ega 640 x 350 x 16 colors vga equivalent to vga16 for 16 color images and vga256 for 256 color images vga16 640 x 480 x 16 vga256 320 x 200 x 256 vga256x 360 x 480 x 256 (most VGA compatible adapters) svga 640 x 480 x 256 (autodetect type - must have at least 512K) Specific SuperVGA adapters may also be selected in 640 x 480 x 256 color mode: aheada, aheadb, ativga, chipstech, everex, oaktech, paradise, trident, tseng, tseng4, video7 Appendixes ---------- Release Notes ------------- Version 2.1 December 1990. One page limitation on GIF directory display removed. Ordered dither and random dither parameters added. Miscellaneous bugs corrected. Version 2.0 December 1990. Support added for 256 color mode on most SVGA adapters with at least 512K of memory, and on VGA adapters, including the special 360 x 480 x 256 color mode. Commands may be entered and edited interactively for files selected from a directory listing. On-line help system added. Version 1.0 October 1990. 640 x 350 x 16 color display mode on EGA displays. Commands entered from DOS command line only. Trademarks: ---------- pixFX is a trademark of Golden Hind International. GIF is a service mark of Compuserve Incorporated. IBM PC is a trademark of International Business Machines Corporation. UNIX is a trademark of AT&T. Distribution ------------ The file PIXLZH.COM is a self-extracting archive containing the following files: READ.ME Licensing and distribution information PIXFX.DOC Instructions for installation and use (this file) PIXFX.EXE Executable module of pixFX * * *