ref: 94916808dd9a53ac297ab537851791894b919828
dir: /sys/src/cmd/jpg/rgbycc.c/
#include <u.h> #include <libc.h> #include <draw.h> float c1 = 1.402; float c2 = 0.34414; float c3 = 0.71414; float c4 = 1.772; int closest(int Y, int Cb, int Cr) { double r, g, b; double diff, min; int rgb, R, G, B, v, i; int y1, cb1, cr1; Cb -= 128; Cr -= 128; r = Y+c1*Cr; g = Y-c2*Cb-c3*Cr; b = Y+c4*Cb; //print("YCbCr: %d %d %d, RGB: %g %g %g\n", Y, Cb, Cr, r, g, b); min = 1000000.; v = 1000; for(i=0; i<256; i++){ rgb = cmap2rgb(i); R = (rgb >> 16) & 0xFF; G = (rgb >> 8) & 0xFF; B = (rgb >> 0) & 0xFF; diff = (R-r)*(R-r) + (G-g)*(G-g) + (B-b)*(B-b); y1 = 0.5870*G + 0.114*B + 0.299*R; cb1 = (B-y1)/1.772; cr1 = (R-y1)/1.402; if(diff < min){ // if(Y==0 && y1!=0) // continue; if(Y==256-16 && y1<256-16) continue; // if(Cb==0 && cb1!=0) // continue; if(Cb==256-16 && cb1<256-16) continue; // if(Cr==0 && cr1!=0) // continue; if(Cr==256-16 && cr1<256-16) continue; //print("%d %d %d\n", R, G, B); min = diff; v = i; } } if(v > 255) abort(); return v; } void main(int argc, char *argv[]) { int i, rgb; int r, g, b; double Y, Cr, Cb; int y, cb, cr; uchar close[16*16*16]; //print("%d\n", closest(atoi(argv[1]), atoi(argv[2]), atoi(argv[3]))); //exits("X"); /* ycbcrmap */ print("uint ycbcrmap[256] = {\n"); for(i=0; i<256; i++){ if(i%8 == 0) print("\t"); rgb = cmap2rgb(i); r = (rgb>>16) & 0xFF; g = (rgb>>8) & 0xFF; b = (rgb>>0) & 0xFF; Y = 0.5870*g + 0.114*b + 0.299*r; Cr = (r-Y)/1.402 + 128.; Cb = (b-Y)/1.772 + 128.; if(Y<0. || Y>=256. || Cr<0. || Cr>=256. || Cb<0. || Cb>=256.) print("bad at %d: %d %d %d; %g %g %g\n", i, r, g, b, Y, Cb, Cr); r = Y; g = Cb; b = Cr; print("0x%.6ulX, ", (r<<16) | (g<<8) | b); if(i%8 == 7) print("\n"); } print("};\n\n"); /* closestycbcr */ print("uchar closestycbcr[16*16*16] = {\n"); for(y=0; y<256; y+=16) for(cb=0; cb<256; cb+=16) for(cr=0; cr<256; cr+=16) close[(cr/16)+16*((cb/16)+16*(y/16))] = closest(y, cb, cr); if(0){ /*weird: set white for nearly white */ for(cb=128-32; cb<=128+32; cb+=16) for(cr=128-32; cr<=128+32; cr+=16) close[(cr/16)+16*((cb/16)+16*(255/16))] = 0; /*weird: set black for nearly black */ for(cb=128-32; cb<=128+32; cb+=16) for(cr=128-32; cr<=128+32; cr+=16) close[(cr/16)+16*((cb/16)+16*(0/16))] = 255; } for(i=0; i<16*16*16; i++){ if(i%16 == 0) print("\t"); print("%d,", close[i]); if(i%16 == 15) print("\n"); } print("};\n\n"); exits(nil); }