cmap - format of .cmap files (color maps)
Color-map files define the mapping between eight-bit color numbers and red,
green and blue intensities used for those numbers. They are read by Magic as
part of system startup, and also by the :load and :save commands
in color-map windows. Color-map file names usually have the form
x. y.z.cmapn, where x
is a class of technology files, y is a class of displays, z is a
class of monitors, and n is a version number (currently 1). The
version number will change in the future if the format of color-map files ever
changes. Normally, x and y correspond to the corresponding parts
of a display styles file. For example, the color map file
mos.7bit.std.cmap1 is used today for most nMOS and CMOS technology
files using displays that support at least seven bits of color per pixel and
standard-phosphor monitors. It corresponds to the display styles file
mos.7bit.dstyle5.
Color-map files are stored in ASCII form, with each line
containing four decimal integers separated by white space. The first three
integers are red, green, and blue intensities, and the fourth field is a
color number. For current displays the intensities must be integers between
0 and 255. The color numbers must increase from line to line, and the last
line must have a color number of 255. The red, green, and blue intensities
on the first line are used for all colors from 0 up to and including the
color number on that line. For other lines, the intensities on that line are
used for all colors starting one color above the color number on the
previous line and continuing up and through the color number on the current
line. For example, consider the color map below:
255 0 0 2
0 0 255 3
255 255 255 256
This color map indicates that colors 0, 1, and 2 are to be red,
color 3 is to be blue, and all other colors are to be white.