Colors and Palettes
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This section applies to true colors - see Dot Patterns for the nature of "colors" or shades in black-and-white display and output.

In principle, Macintosh and Windows allow full freedom to specify colors for lines and fills in color display or output. In practice, it is advisable to select colors carefully to take best advantage of a wide range of display and output devices. For 8-bit or 256 color screen displays, it is also necessary to supply a palette of the desired colors to the system to avoid unnecessary color mixing or dithering.

SHAPE uses a primary palette of 16 colors to assist in color selection, and from which a 256-color palette is derived.

Display or screen devices in the past were most easily or directly able to produce colors which have the simplest combinations of components red, green and blue. The binary combinations of red, green and blue are cyan(green+blue), magenta or violet (red+blue) and yellow (red+green). On the other hand, the primary colors for printing are cyan, magenta and yellow. Screen devices such as VGA and super-VGA can now produce any color, but it is still best to select the six colors red, green, blue, cyan, magenta and yellow, plus black and white, as first choices for colors of lines and fills in SHAPE. These are the first 8 colors in the SHAPE palette. Actually, black is not a good color for fills, since it cannot be shaded. The next-best group of full-intensity colors consists of the six colors which are binary combinations of the six mentioned above. These 6, plus two shades of gray, are the second 8 colors in the SHAPE palette.

At this time, 8-bit color, allowing a total of 256 separate colors, is still sometimes used for screen display and is often convenient for raster files. SHAPE generates a color palette for 8-bit display and output as follows. If the number of shading zones selected in the Shading dialog in the Input2 menu is 16 or less, 15 colors are derived from each of the colors in the primary 16-color palette, except for black, ranging from the pure or full-intensity color to near black. There are thus 15 gradations of red, for example, with rgb values of (255,0,0), (238,0,0), down to (17,0,0). Including black (0,0,0), this allows a different shade for each of the 16 zones.

If the number of shading zones selected in the Shading dialog in the Input2 menu is 32, only the first eight colors in the palette, excluding black, are used to derive the shaded colors, and there are 31 gradations of each. (Note that this is different from the DOS versions of SHAPE, in which the second 8 colors were used for the 32-zone palette; however, the colors used, namely red, green, blue, cyan, magenta, yellow and white are the same, and there should be no problem with SHAPE-DOS files).

To summarize, colors used in SHAPE should be as simple as possible for best success on a wide range of display and output devices. Choose colors first from the first eight colors in the standard SHAPE palette, then from the second eight.

You do have the freedom to define any color as desired, specifying the RGB components. You can also redefine or rearrange the SHAPE 16-color palette with the Palette dialog in the Settings menu, and this will give correct results for 8-bit (256-color) screen display. However, it is probable that more complex colors will not be rendered very satisfactorily on color hard-copy devices (depending, of course, on the sophistication of the device).