Initial import.
diff --git a/src/libdraw/rgb.c b/src/libdraw/rgb.c
new file mode 100644
index 0000000..e8f7f51
--- /dev/null
+++ b/src/libdraw/rgb.c
@@ -0,0 +1,99 @@
+#include <u.h>
+#include <libc.h>
+#include <draw.h>
+
+/*
+ * This original version, although fast and a true inverse of
+ * cmap2rgb, in the sense that rgb2cmap(cmap2rgb(c))
+ * returned the original color, does a terrible job for RGB
+ * triples that do not appear in the color map, so it has been
+ * replaced by the much slower version below, that loops
+ * over the color map looking for the nearest point in RGB
+ * space. There is no visual psychology reason for that
+ * criterion, but it's easy to implement and the results are
+ * far more pleasing.
+ *
+int
+rgb2cmap(int cr, int cg, int cb)
+{
+ int r, g, b, v, cv;
+
+ if(cr < 0)
+ cr = 0;
+ else if(cr > 255)
+ cr = 255;
+ if(cg < 0)
+ cg = 0;
+ else if(cg > 255)
+ cg = 255;
+ if(cb < 0)
+ cb = 0;
+ else if(cb > 255)
+ cb = 255;
+ r = cr>>6;
+ g = cg>>6;
+ b = cb>>6;
+ cv = cr;
+ if(cg > cv)
+ cv = cg;
+ if(cb > cv)
+ cv = cb;
+ v = (cv>>4)&3;
+ return ((((r<<2)+v)<<4)+(((g<<2)+b+v-r)&15));
+}
+*/
+
+int
+rgb2cmap(int cr, int cg, int cb)
+{
+ int i, r, g, b, sq;
+ u32int rgb;
+ int best, bestsq;
+
+ best = 0;
+ bestsq = 0x7FFFFFFF;
+ for(i=0; i<256; i++){
+ rgb = cmap2rgb(i);
+ r = (rgb>>16) & 0xFF;
+ g = (rgb>>8) & 0xFF;
+ b = (rgb>>0) & 0xFF;
+ sq = (r-cr)*(r-cr)+(g-cg)*(g-cg)+(b-cb)*(b-cb);
+ if(sq < bestsq){
+ bestsq = sq;
+ best = i;
+ }
+ }
+ return best;
+}
+
+int
+cmap2rgb(int c)
+{
+ int j, num, den, r, g, b, v, rgb;
+
+ r = c>>6;
+ v = (c>>4)&3;
+ j = (c-v+r)&15;
+ g = j>>2;
+ b = j&3;
+ den=r;
+ if(g>den)
+ den=g;
+ if(b>den)
+ den=b;
+ if(den==0) {
+ v *= 17;
+ rgb = (v<<16)|(v<<8)|v;
+ }
+ else{
+ num=17*(4*den+v);
+ rgb = ((r*num/den)<<16)|((g*num/den)<<8)|(b*num/den);
+ }
+ return rgb;
+}
+
+int
+cmap2rgba(int c)
+{
+ return (cmap2rgb(c)<<8)|0xFF;
+}
