Programmer 7500

home *** CD-ROM | disk | FTP | other *** search

/ Programmer 7500 / MAX_PROGRAMMERS.iso / PASCAL / HTMIX20.ZIP / VGACOLS.ZIP / VGACOLS.DOC < prev next >

Wrap

Text File | 1992-07-14 | 8.3 KB | 241 lines

┌──────────────────┐ │ VGA Colors 2.0 │ └──────────────────┘ INTRODUCTION ──────────── The program VGACOLS and the unit COLORS are used to obtain complete control over the EGA palette registers. With the program VGACOLS you can design your own 16 color palettes, and save them to file. With the procedures in COLORS you can get access to those stored palettes, or define new ones in your own program. SOME TECHNICAL STUFF ──────────────────── There are 16 8-bit palette registers on the EGA displays, and each if these 16 registers can take on 1 of 64 values, defined by: Bit 7 Reserved Bit 6 Reserved Bit 5 Secondary Red Bit 4 Secondary Green Bit 3 Secondary Blue Bit 2 Primary Red Bit 1 Primary Green Bit 1 Primary Blue The primary colors have an intensity of 2/3, while the secondary have an intensity of 1/3. For example, a register value of $02 will produce green, $10 will produce a dim green, and $12 will produce a bright green. The default color value for the 16 palette registers are: Palette register Color value Color ────────────────────────────────────────────────── $00 $00 Black $01 $01 Blue $02 $02 Green $03 $03 Cyan $04 $04 Red $05 $05 Magenta $06 $14 Brown $07 $07 White $08 $38 Dark Gray $09 $39 Light Blue $0A $3A Light Green $0B $3B Light Cyan $0C $3C Light Red $0D $3D Light Magenta $0E $3E Yellow $0F $3F Bright White ────────────────────────────────────────────────── Table 1. Each of the colors can be defined by a red, green and blue component, each in the range from 0 to 63. In the Turbo Pascal GRAPH unit there are some routines, SetPalette and SetRGBPalette, which are used to change the default Color values in the Palette registers, and to set the red, green and blue components. in text mode, however, no similar routines exist. ┌───────────────┐ │ UNIT Colors │ └───────────────┘ This unit defines the routines necessary to control the color palettes. procedure GetTEXTPalette(PaletteReg: byte; var ColorNum: byte); procedure SetTEXTPalette(PaletteReg,ColorNum: byte); ──────────────────────────────────────────────────────────────── These are equivalent to the TP routines GetPalette and SetPalette. GetTEXTPalette makes an INT $10 call, with the register entry: AL = $07 BL = PaletteReg and will return the Color value currently in PaletteReg ColorNum = BH SetTEXTPalette also makes an INT $10 call, with the register entry: AL = $00 BL = PaletteReg BH = ColorNum which will set the Color value in PaletteReg. procedure GetDACRegister(ColorNum: byte; var RedValue,GreenValue,BlueValue: byte); procedure SetDACRegister(ColorNum,RedValue,GreenValue, BlueValue: byte); ──────────────────────────────────────────────────────── These are equivalent to the TP routines GetRGBPalette and SetRGBPalette. GetDACRegister makes an INT $10 call, with the register entry: AL = $15 BX = ColorNum and returns RedValue = DH GreenValue= CH BlueValue = CL SetDACRegister makes an INT $10 call, with the register entry: AL = $15 BX = ColorNum DH = RedValue CH = GreenValue CL = BlueValue Turbo Pascal defines the colors as: Black = 0 DarkGray = 8 Blue = 1 LightBlue = 9 Green = 2 LightGreen = 10 Cyan = 3 LightCyan = 11 Red = 4 LightRed = 12 Magenta = 5 LightMagenta = 13 Brown = 6 Yellow = 14 LightGray = 7 White = 15 but as can be seen in table 1, these are the register values, not the color values, which range from 0 to 63. So if you try the command SetRGBRegister(LightBlue,10,10,50); this will not give the result you would expect, since LightBlue is define to be $09, while the color value of light blue is $39. There are two ways to solve this: The first is to redefine the color value in the palette registers, and then set the RGB value of that color: SetTEXTPalette(LightBlue,LightBlue); SetRGBRegister(LightBlue,10,10,50); Another, (and in my opinion cleaner way) is to use the constant array CList defined in the Colors unit. This array contains the values in table 1. So in order to perform the task above, just give the command SetRGBRegister(CList[LightBlue],10,10,50); procedure GetColorList; procedure SetColorList; ─────────────────────── The Colors unit defines: type TColor = record R,G,B : byte; end; var ColorList: array[0..15] of TColor; GetColorList will read the DAC registers (using GetRGBRegister) and store them in ColorList, while SetColorList will call SetRGBRegister and set the DAC registers to the values stored in ColorList. function ReadDACFile(Filename: string): boolean; procedure WriteDACFile(Filename: string); ──────────────────────────────────────────────── ReadDACFile will read a color palette from the file Filename, and return true if the operation was successful. The values read will be stored in ColorList, but will NOT automatically be loaded. Call SetColorList to do that! WriteDACFile will write the color palette stored in ColorList to the file Filename. ┌───────────────────┐ │ PROGRAM VGACols │ └───────────────────┘ This program lets you create and edit color palettes. The palettes can be stored to file and used in your own programs. When the program starts, it will display the 16 colors, and the RGB component values of the current color. You can switch between selecting the color and editing the color with the Tab key. To select a color, use the arrow keys to move, and either Return or Tab to select. This will bring you to bottom of the screen, where you can change the individual Red, Green and Blue components of the current color. Use the up and down arrow keys to select Red, Green or Blue, and the left and right arrow keys to change the value. To save the palette to file, press F2. The program will prompt you for a filename. To load a palette from file, press F3. The program will give you a list of files to choose from. The default extension of the palette files are .VGA, but by pressing F3 again, you can look for other files. Press Escape to quit the program.