1 058b0118 2005-01-03 devnull .TH READCOLMAP 3
 2 058b0118 2005-01-03 devnull .SH NAME
 3 058b0118 2005-01-03 devnull RGB, readcolmap, writecolmap \- access display color map
 4 058b0118 2005-01-03 devnull .SH SYNOPSIS
 5 058b0118 2005-01-03 devnull .B #include <u.h>
 6 058b0118 2005-01-03 devnull .br
 7 058b0118 2005-01-03 devnull .B #include <libc.h>
 8 058b0118 2005-01-03 devnull .br
 9 058b0118 2005-01-03 devnull .B #include <draw.h>
10 058b0118 2005-01-03 devnull .PP
11 058b0118 2005-01-03 devnull .PP
12 058b0118 2005-01-03 devnull .ta \w'\fLvoid 'u
13 058b0118 2005-01-03 devnull .PP
14 058b0118 2005-01-03 devnull .B
15 058b0118 2005-01-03 devnull int	readcolmap(Display *d, RGB *map)
16 058b0118 2005-01-03 devnull .PP
17 058b0118 2005-01-03 devnull .B
18 058b0118 2005-01-03 devnull int	writecolmap(Display *d, RGB *map)
19 058b0118 2005-01-03 devnull .fi
20 058b0118 2005-01-03 devnull .SH DESCRIPTION
21 058b0118 2005-01-03 devnull Colors are described by their red, green, and blue
22 058b0118 2005-01-03 devnull light intensities, in an
23 058b0118 2005-01-03 devnull .B RGB
24 058b0118 2005-01-03 devnull datum:
25 058b0118 2005-01-03 devnull .IP
26 058b0118 2005-01-03 devnull .EX
27 058b0118 2005-01-03 devnull .ta 6n
28 058b0118 2005-01-03 devnull typedef
29 058b0118 2005-01-03 devnull struct RGB {
30 058b0118 2005-01-03 devnull 	ulong red;
31 058b0118 2005-01-03 devnull 	ulong green;
32 058b0118 2005-01-03 devnull 	ulong blue;
33 058b0118 2005-01-03 devnull } RGB;
34 058b0118 2005-01-03 devnull .EE
35 058b0118 2005-01-03 devnull .PP
36 058b0118 2005-01-03 devnull Black is represented by zero in all three positions and
37 058b0118 2005-01-03 devnull white has the maximum
38 058b0118 2005-01-03 devnull .B unsigned
39 058b0118 2005-01-03 devnull .B long
40 058b0118 2005-01-03 devnull value in all three positions.
41 058b0118 2005-01-03 devnull .PP
42 058b0118 2005-01-03 devnull A color map is an array of
43 058b0118 2005-01-03 devnull .BR RGB s,
44 058b0118 2005-01-03 devnull of length
45 058b0118 2005-01-03 devnull .if t \x'-.8n'2\u\s-1\fIdepth\fP\s+1\d,
46 058b0118 2005-01-03 devnull .if n 2^\fIdepth\fP,
47 058b0118 2005-01-03 devnull giving the colors for pixels 0, 1, 2, etc.
48 058b0118 2005-01-03 devnull On displays with color mapped pixels
49 058b0118 2005-01-03 devnull (typically 8-bit displays),
50 058b0118 2005-01-03 devnull one retrieves RGB color information
51 058b0118 2005-01-03 devnull by treating the pixel data as an offset
52 058b0118 2005-01-03 devnull into the color map.
53 058b0118 2005-01-03 devnull .PP
54 058b0118 2005-01-03 devnull .I Readcolmap
55 058b0118 2005-01-03 devnull reads the color map for the given display into the provided
56 058b0118 2005-01-03 devnull .IR map ,
57 058b0118 2005-01-03 devnull which must have enough space to hold it.
58 058b0118 2005-01-03 devnull .I Writecolmap
59 058b0118 2005-01-03 devnull associates the given color map with the given display, if possible.
60 058b0118 2005-01-03 devnull (The hardware might not allow this.)
61 058b0118 2005-01-03 devnull Both return 0 on success, or \-1 on error, setting
62 058b0118 2005-01-03 devnull .IR errstr .
63 058b0118 2005-01-03 devnull .PP
64 058b0118 2005-01-03 devnull Changing the hardware color map does not change
65 058b0118 2005-01-03 devnull the color map used by the
66 d32deab1 2020-08-16 rsc .MR draw (3)
67 058b0118 2005-01-03 devnull operator to convert between
68 058b0118 2005-01-03 devnull mapped and true color or greyscale images,
69 058b0118 2005-01-03 devnull which is described in 
70 d32deab1 2020-08-16 rsc .MR color (7) .
71 058b0118 2005-01-03 devnull .SH SOURCE
72 c3674de4 2005-01-11 devnull .B \*9/src/libdraw
73 058b0118 2005-01-03 devnull .SH "SEE ALSO"
74 d32deab1 2020-08-16 rsc .MR graphics (3) ,
75 d32deab1 2020-08-16 rsc .MR draw (3) ,
76 d32deab1 2020-08-16 rsc .MR color (7)