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James Gregory 2013-12-31 11:38:48 +11:00
commit f658bfbb40
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55-03.md
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@ -12,28 +12,30 @@ pages: 1038-1040
**LISTING 55.3 L55-3.C**
/* Converts a model color (a color in the RGB color cube, in the current
color model) to a color index for mode X. Pure primary colors are
special-cased, and everything else is handled by a 2-2-2 model. */
int ModelColorToColorIndex(ModelColor * Color)
{
if (Color->Red == 0) {
if (Color->Green == 0) {
/* Pure blue */
return(192+(Color->Blue >> 2));
} else if (Color->Blue == 0) {
/* Pure green */
return(128+(Color->Green >> 2));
}
} else if ((Color->Green == 0) && (Color->Blue == 0)) {
/* Pure red */
return(64+(Color->Red >> 2));
}
/* Multi-color mix; look up the index with the two most significant bits
of each color component */
return(((Color->Red & 0xC0) >> 2) | ((Color->Green & 0xC0) >> 4) |
((Color->Blue & 0xC0) >> 6));
```c
/* Converts a model color (a color in the RGB color cube, in the current
color model) to a color index for mode X. Pure primary colors are
special-cased, and everything else is handled by a 2-2-2 model. */
int ModelColorToColorIndex(ModelColor * Color)
{
if (Color->Red == 0) {
if (Color->Green == 0) {
/* Pure blue */
return(192+(Color->Blue >> 2));
} else if (Color->Blue == 0) {
/* Pure green */
return(128+(Color->Green >> 2));
}
} else if ((Color->Green == 0) && (Color->Blue == 0)) {
/* Pure red */
return(64+(Color->Red >> 2));
}
/* Multi-color mix; look up the index with the two most significant bits
of each color component */
return(((Color->Red & 0xC0) >> 2) | ((Color->Green & 0xC0) >> 4) |
((Color->Blue & 0xC0) >> 6));
}
```
In DEMO1, three-quarters of the palette is set up with 64 intensity
levels of each of the three pure primary colors (red, green, and blue),