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NAME
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RGB, readcolmap, writecolmap – access display color map
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SYNOPSIS
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#include <u.h>
#include <libc.h>
#include <draw.h>
int readcolmap(Display *d, RGB *map)
int writecolmap(Display *d, RGB *map)
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DESCRIPTION
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Colors are described by their red, green, and blue light intensities,
in an RGB datum:
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typedef
struct RGB {
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ulong red;
ulong green;
ulong blue;
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} RGB;
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Black is represented by zero in all three positions and white
has the maximum unsigned long value in all three positions.
A color map is an array of RGBs, of length 2depth, giving the
colors for pixels 0, 1, 2, etc. On displays with color mapped
pixels (typically 8-bit displays), one retrieves RGB color information
by treating the pixel data as an offset into the color map.
Readcolmap reads the color map for the given display into the
provided map, which must have enough space to hold it. Writecolmap
associates the given color map with the given display, if possible.
(The hardware might not allow this.) Both return 0 on success,
or –1 on error, setting errstr.
Changing the hardware color map does not change the color map
used by the draw(3) operator to convert between mapped and true
color or greyscale images, which is described in color(7).
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SOURCE
SEE ALSO
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