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56 lines
1.3 KiB
Groff
56 lines
1.3 KiB
Groff
.TH COLOR 3
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.SH NAME
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cmap2rgb, cmap2rgba, rgb2cmap \- colors and color maps
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.SH SYNOPSIS
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.B #include <u.h>
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.br
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.B #include <libc.h>
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.br
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.B #include <draw.h>
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.PP
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.B
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int rgb2cmap(int red, int green, int blue)
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.PP
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.B
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int cmap2rgb(int col)
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.PP
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.B
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int cmap2rgba(int col)
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.SH DESCRIPTION
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These routines convert between `true color' red/green/blue triples and the Plan 9 color map.
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See
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.MR color (7)
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for a description of RGBV, the standard color map.
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.PP
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.I Rgb2cmap
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takes a trio of color values, scaled from 0 (no intensity) to 255 (full intensity),
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and returns the index of the color in RGBV closest to that represented
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by those values.
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.PP
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.I Cmap2rgb
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decomposes the color of RGBV index
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.I col
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and returns a 24-bit integer with the low 8 bits representing the blue value,
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the next 8 representing green, and the next 8 representing red.
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.I Cmap2rgba
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decomposes the color of RGBV index
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.I col
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and returns a 32-bit integer with the low 8 bits representing an alpha value,
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defined to be 255,
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and the next 8 representing blue, then green, then red, as for
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.I cmap2rgba
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shifted up 8 bits.
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This 32-bit representation is the format used by
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.MR draw (3)
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and
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.MR memdraw (3)
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library routines that
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take colors as arguments.
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.SH SOURCE
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.B \*9/src/libdraw
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.SH SEE ALSO
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.MR graphics (3) ,
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.MR allocimage (3) ,
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.MR draw (3) ,
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.MR image (7) ,
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.MR color (7)
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