src/tiff/tools/ycbcr.c

   1 float   ycbcrCoeffs[3] = { .299, .587, .114 };
   2 /* default coding range is CCIR Rec 601-1 with no headroom/footroom */
   3 unsigned long refBlackWhite[6] = { 0, 255, 128, 255, 128, 255 };
   4
   5 #define LumaRed         ycbcrCoeffs[0]
   6 #define LumaGreen       ycbcrCoeffs[1]
   7 #define LumaBlue        ycbcrCoeffs[2]
   8
   9 long    eRtotal = 0;
  10 long    eGtotal = 0;
  11 long    eBtotal = 0;
  12 long    preveRtotal = 0;
  13 long    preveGtotal = 0;
  14 long    preveBtotal = 0;
  15 unsigned long AbseRtotal = 0;
  16 unsigned long AbseGtotal = 0;
  17 unsigned long AbseBtotal = 0;
  18 unsigned long eCodes = 0;
  19 unsigned long preveCodes = 0;
  20 unsigned long eBits = 0;
  21 unsigned long preveBits = 0;
  22
  23 static  void setupLumaTables();
  24 static int abs(int v) { return (v < 0 ? -v : v); }
  25 static double pct(int v,double range) { return (v*100. / range); }
  26 static void check(int R, int G, int B);
  27
  28 float   D1, D2;
  29 float   D3, D4;
  30 float   D5, D6;
  31
  32 int
  33 main(int argc, char** argv)
  34 {
  35     int R, G, B;
  36
  37     if (argc > 1) {
  38         refBlackWhite[0] = 16;
  39         refBlackWhite[1] = 235;
  40         refBlackWhite[2] = 128;
  41         refBlackWhite[3] = 240;
  42         refBlackWhite[4] = 128;
  43         refBlackWhite[5] = 240;
  44     }
  45     D3 = 2 - 2*LumaRed;
  46     D4 = 2 - 2*LumaBlue;
  47     D1 = 1. / D3;
  48     D2 = 1. / D4;
  49     D5 = D3*LumaRed / LumaGreen;
  50     D6 = D4*LumaBlue / LumaGreen;
  51     setupLumaTables();
  52     for (R = 0; R < 256; R++) {
  53         for (G = 0; G < 256; G++)
  54             for (B = 0; B < 256; B++)
  55                 check(R, G, B);
  56         printf("[%3u] c %u/%u b %u/%u (R %u/%d/%u G %u/%d/%u B %u/%d/%u)\n"
  57             , R
  58             , eCodes - preveCodes, eCodes
  59             , eBits - preveBits, eBits
  60             , abs(AbseRtotal - preveRtotal), eRtotal , AbseRtotal
  61             , abs(AbseGtotal - preveGtotal), eGtotal , AbseGtotal
  62             , abs(AbseBtotal - preveBtotal), eBtotal , AbseBtotal
  63         );
  64         preveRtotal = AbseRtotal;
  65         preveGtotal = AbseGtotal;
  66         preveBtotal = AbseBtotal;
  67         preveCodes = eCodes;
  68         preveBits = eBits;
  69     }
  70     printf("%u total codes\n", 256*256*256);
  71     printf("total error: %u codes %u bits (R %d/%u G %d/%u B %d/%u)\n"
  72         , eCodes
  73         , eBits
  74         , eRtotal , AbseRtotal
  75         , eGtotal , AbseGtotal
  76         , eBtotal , AbseBtotal
  77     );
  78     return (0);
  79 }
  80
  81 float   *lumaRed;
  82 float   *lumaGreen;
  83 float   *lumaBlue;
  84
  85 static float*
  86 setupLuma(float c)
  87 {
  88     float *v = (float *)_TIFFmalloc(256 * sizeof (float));
  89     int i;
  90     for (i = 0; i < 256; i++)
  91         v[i] = c * i;
  92     return (v);
  93 }
  94
  95 static void
  96 setupLumaTables(void)
  97 {
  98     lumaRed = setupLuma(LumaRed);
  99     lumaGreen = setupLuma(LumaGreen);
 100     lumaBlue = setupLuma(LumaBlue);
 101 }
 102
 103 static unsigned
 104 V2Code(float f, unsigned long RB, unsigned long RW, int CR)
 105 {
 106     unsigned int c = (unsigned int)((((f)*(RW-RB)/CR)+RB)+.5);
 107     return (c > 255 ? 255 : c);
 108 }
 109
 110 #define Code2V(c, RB, RW, CR)   ((((c)-(int)RB)*(float)CR)/(float)(RW-RB))
 111
 112 #define CLAMP(f,min,max) \
 113     (int)((f)+.5 < (min) ? (min) : (f)+.5 > (max) ? (max) : (f)+.5)
 114
 115 static
 116 void
 117 check(int R, int G, int B)
 118 {
 119     float Y, Cb, Cr;
 120     int iY, iCb, iCr;
 121     float rY, rCb, rCr;
 122     float rR, rG, rB;
 123     int eR, eG, eB;
 124
 125     Y = lumaRed[R] + lumaGreen[G] + lumaBlue[B];
 126     Cb = (B - Y)*D2;
 127     Cr = (R - Y)*D1;
 128     iY = V2Code(Y, refBlackWhite[0], refBlackWhite[1], 255);
 129     iCb = V2Code(Cb, refBlackWhite[2], refBlackWhite[3], 127);
 130     iCr = V2Code(Cr, refBlackWhite[4], refBlackWhite[5], 127);
 131     rCb = Code2V(iCb, refBlackWhite[2], refBlackWhite[3], 127);
 132     rCr = Code2V(iCr, refBlackWhite[4], refBlackWhite[5], 127);
 133     rY = Code2V(iY, refBlackWhite[0], refBlackWhite[1], 255);
 134     rR = rY + rCr*D3;
 135     rB = rY + rCb*D4;
 136     rG = rY - rCb*D6 - rCr*D5;
 137     eR = R - CLAMP(rR,0,255);
 138     eG = G - CLAMP(rG,0,255);
 139     eB = B - CLAMP(rB,0,255);
 140     if (abs(eR) > 1 || abs(eG) > 1 || abs(eB) > 1) {
 141         printf("R %u G %u B %u", R, G, B);
 142         printf(" Y %g Cb %g Cr %g", Y, Cb, Cr);
 143         printf(" iY %u iCb %u iCr %u", iY, iCb, iCr);
 144         printf("\n -> Y %g Cb %g Cr %g", rY, rCb, rCr);
 145         printf(" R %g (%u) G %g (%u) B %g (%u) E=[%d %d %d])\n"
 146             , rR, CLAMP(rR,0,255)
 147             , rG, CLAMP(rG,0,255)
 148             , rB, CLAMP(rB,0,255)
 149             , eR, eG, eB
 150         );
 151     }
 152     eRtotal += eR;
 153     eGtotal += eG;
 154     eBtotal += eB;
 155     AbseRtotal += abs(eR);
 156     AbseGtotal += abs(eG);
 157     AbseBtotal += abs(eB);
 158     if (eR | eG | eB)
 159         eCodes++;
 160     eBits += abs(eR) + abs(eG) + abs(eB);
 161 }
 162 /*
 163  * Local Variables:
 164  * mode: c
 165  * c-basic-offset: 8
 166  * fill-column: 78
 167  * End:
 168  */