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author | rsc <devnull@localhost> | 2005-01-03 06:40:20 +0000 |
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committer | rsc <devnull@localhost> | 2005-01-03 06:40:20 +0000 |
commit | 058b0118a52061ad57694c01fc8763b22b789c4d (patch) | |
tree | 6685f04dea5ed68edaa34998c976aed34c55fe94 /man/man3/readcolmap.3 | |
parent | 2600337aa704efbeba8201e88147a764b4fd2b90 (diff) | |
download | plan9port-058b0118a52061ad57694c01fc8763b22b789c4d.tar.gz plan9port-058b0118a52061ad57694c01fc8763b22b789c4d.tar.bz2 plan9port-058b0118a52061ad57694c01fc8763b22b789c4d.zip |
Some man pages.
Diffstat (limited to 'man/man3/readcolmap.3')
-rw-r--r-- | man/man3/readcolmap.3 | 76 |
1 files changed, 76 insertions, 0 deletions
diff --git a/man/man3/readcolmap.3 b/man/man3/readcolmap.3 new file mode 100644 index 00000000..51753c57 --- /dev/null +++ b/man/man3/readcolmap.3 @@ -0,0 +1,76 @@ +.TH READCOLMAP 3 +.SH NAME +RGB, readcolmap, writecolmap \- access display color map +.SH SYNOPSIS +.B #include <u.h> +.br +.B #include <libc.h> +.br +.B #include <draw.h> +.PP +.PP +.ta \w'\fLvoid 'u +.PP +.B +int readcolmap(Display *d, RGB *map) +.PP +.B +int writecolmap(Display *d, RGB *map) +.fi +.SH DESCRIPTION +Colors are described by their red, green, and blue +light intensities, in an +.B RGB +datum: +.IP +.EX +.ta 6n +typedef +struct RGB { + ulong red; + ulong green; + ulong blue; +} RGB; +.EE +.PP +Black is represented by zero in all three positions and +white has the maximum +.B unsigned +.B long +value in all three positions. +.PP +A color map is an array of +.BR RGB s, +of length +.if t \x'-.8n'2\u\s-1\fIdepth\fP\s+1\d, +.if n 2^\fIdepth\fP, +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. +.PP +.I Readcolmap +reads the color map for the given display into the provided +.IR map , +which must have enough space to hold it. +.I 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 +.IR errstr . +.PP +Changing the hardware color map does not change +the color map used by the +.IR draw (3) +operator to convert between +mapped and true color or greyscale images, +which is described in +.IR color (7). +.SH SOURCE +.B /usr/local/plan9/src/libdraw +.SH "SEE ALSO" +.IR graphics (3), +.IR draw (3), +.IR color (7) |