color.3 (1338B)
1 .TH COLOR 3 2 .SH NAME 3 cmap2rgb, cmap2rgba, rgb2cmap \- colors and color maps 4 .SH SYNOPSIS 5 .B #include <u.h> 6 .br 7 .B #include <libc.h> 8 .br 9 .B #include <draw.h> 10 .PP 11 .B 12 int rgb2cmap(int red, int green, int blue) 13 .PP 14 .B 15 int cmap2rgb(int col) 16 .PP 17 .B 18 int cmap2rgba(int col) 19 .SH DESCRIPTION 20 These routines convert between `true color' red/green/blue triples and the Plan 9 color map. 21 See 22 .MR color (7) 23 for a description of RGBV, the standard color map. 24 .PP 25 .I Rgb2cmap 26 takes a trio of color values, scaled from 0 (no intensity) to 255 (full intensity), 27 and returns the index of the color in RGBV closest to that represented 28 by those values. 29 .PP 30 .I Cmap2rgb 31 decomposes the color of RGBV index 32 .I col 33 and returns a 24-bit integer with the low 8 bits representing the blue value, 34 the next 8 representing green, and the next 8 representing red. 35 .I Cmap2rgba 36 decomposes the color of RGBV index 37 .I col 38 and returns a 32-bit integer with the low 8 bits representing an alpha value, 39 defined to be 255, 40 and the next 8 representing blue, then green, then red, as for 41 .I cmap2rgba 42 shifted up 8 bits. 43 This 32-bit representation is the format used by 44 .MR draw (3) 45 and 46 .MR memdraw (3) 47 library routines that 48 take colors as arguments. 49 .SH SOURCE 50 .B \*9/src/libdraw 51 .SH SEE ALSO 52 .MR graphics (3) , 53 .MR allocimage (3) , 54 .MR draw (3) , 55 .MR image (7) , 56 .MR color (7)