man(1) Manual page archive

     COLOR(2)                                                 COLOR(2)

          cmap2rgb, cmap2rgba, rgb2cmap - colors and color maps

          #include <u.h>
          #include <libc.h>
          #include <draw.h>

          int  rgb2cmap(int red, int green, int blue)

          int  cmap2rgb(int col)

          int  cmap2rgba(int col)

          These routines convert between `true color' red/green/blue
          triples and the Plan 9 color map.  See color(6) for a
          description of RGBV, the standard color map.

          Rgb2cmap takes a trio of color values, scaled from 0 (no
          intensity) to 255 (full intensity), and returns the index of
          the color in RGBV closest to that represented by those val-

          Cmap2rgb decomposes the color of RGBV index col and returns
          a 24-bit integer with the low 8 bits representing the blue
          value, the next 8 representing green, and the next 8 repre-
          senting red.  Cmap2rgba decomposes the color of RGBV index
          col and returns a 32-bit integer with the low 8 bits repre-
          senting an alpha value, defined to be 255, and the next 8
          representing blue, then green, then red, as for cmap2rgba
          shifted up 8 bits.  This 32-bit representation is the format
          used by draw(2) and memdraw(2) library routines that take
          colors as arguments.


          graphics(2), allocimage(2), draw(2), image(6), color(6)