Color QuickDraw is a collection of system software routines that your application can use to display hundreds, thousands, even millions of colors on capable screens. Color QuickDraw is available on all newer models of Macintosh computers; only those older computers based on the Motorola 68000 processor provide no support for Color QuickDraw.
Color QuickDraw performs its operations in a graphics port called a color graphics port, which is based on a data structure of type CGrafPort. As with basic graphics ports (which are based on a data structure of type GrafPort), each color graphics port has its own local coordinate system. All fields in a CGrafPort record are expressed in these coordinates, and all calculations and actions that Color QuickDraw performs use its local coordinate system.
Color QuickDraw supplements the black-and-white patterns of basic QuickDraw with pixel patterns, which can use colors at any pixel depth and can be of any width and height that’s a power of 2. A pixel pattern defines a repeating design (such as stripes of different colors) or a color otherwise unavailable on indexed devices. For example, if your application draws to an indexed device that supports 4 bits per pixel, your application has 16 colors available if it simply sets the foreground color and draws. However, if your application uses the MakeRGBPat procedure to create patterns that use these 16 colors in various combinations, and then draws using that pattern, your application can effectively have as many as 125 approximated colors at its disposal. For example, you can specify a purple color to MakeRGBPat, which creates a pattern that mixes blue and red pixels.