169 lines
4.1 KiB
C
169 lines
4.1 KiB
C
float ycbcrCoeffs[3] = { .299, .587, .114 };
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/* default coding range is CCIR Rec 601-1 with no headroom/footroom */
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unsigned long refBlackWhite[6] = { 0, 255, 128, 255, 128, 255 };
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#define LumaRed ycbcrCoeffs[0]
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#define LumaGreen ycbcrCoeffs[1]
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#define LumaBlue ycbcrCoeffs[2]
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long eRtotal = 0;
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long eGtotal = 0;
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long eBtotal = 0;
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long preveRtotal = 0;
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long preveGtotal = 0;
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long preveBtotal = 0;
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unsigned long AbseRtotal = 0;
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unsigned long AbseGtotal = 0;
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unsigned long AbseBtotal = 0;
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unsigned long eCodes = 0;
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unsigned long preveCodes = 0;
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unsigned long eBits = 0;
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unsigned long preveBits = 0;
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static void setupLumaTables();
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static int abs(int v) { return (v < 0 ? -v : v); }
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static double pct(int v,double range) { return (v*100. / range); }
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static void check(int R, int G, int B);
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float D1, D2;
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float D3, D4;
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float D5, D6;
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int
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main(int argc, char** argv)
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{
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int R, G, B;
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if (argc > 1) {
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refBlackWhite[0] = 16;
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refBlackWhite[1] = 235;
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refBlackWhite[2] = 128;
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refBlackWhite[3] = 240;
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refBlackWhite[4] = 128;
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refBlackWhite[5] = 240;
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}
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D3 = 2 - 2*LumaRed;
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D4 = 2 - 2*LumaBlue;
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D1 = 1. / D3;
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D2 = 1. / D4;
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D5 = D3*LumaRed / LumaGreen;
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D6 = D4*LumaBlue / LumaGreen;
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setupLumaTables();
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for (R = 0; R < 256; R++) {
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for (G = 0; G < 256; G++)
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for (B = 0; B < 256; B++)
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check(R, G, B);
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printf("[%3u] c %u/%u b %u/%u (R %u/%d/%u G %u/%d/%u B %u/%d/%u)\n"
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, R
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, eCodes - preveCodes, eCodes
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, eBits - preveBits, eBits
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, abs(AbseRtotal - preveRtotal), eRtotal , AbseRtotal
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, abs(AbseGtotal - preveGtotal), eGtotal , AbseGtotal
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, abs(AbseBtotal - preveBtotal), eBtotal , AbseBtotal
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);
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preveRtotal = AbseRtotal;
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preveGtotal = AbseGtotal;
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preveBtotal = AbseBtotal;
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preveCodes = eCodes;
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preveBits = eBits;
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}
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printf("%u total codes\n", 256*256*256);
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printf("total error: %u codes %u bits (R %d/%u G %d/%u B %d/%u)\n"
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, eCodes
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, eBits
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, eRtotal , AbseRtotal
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, eGtotal , AbseGtotal
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, eBtotal , AbseBtotal
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);
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return (0);
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}
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float *lumaRed;
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float *lumaGreen;
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float *lumaBlue;
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static float*
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setupLuma(float c)
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{
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float *v = (float *)_TIFFmalloc(256 * sizeof (float));
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int i;
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for (i = 0; i < 256; i++)
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v[i] = c * i;
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return (v);
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}
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static void
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setupLumaTables(void)
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{
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lumaRed = setupLuma(LumaRed);
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lumaGreen = setupLuma(LumaGreen);
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lumaBlue = setupLuma(LumaBlue);
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}
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static unsigned
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V2Code(float f, unsigned long RB, unsigned long RW, int CR)
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{
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unsigned int c = (unsigned int)((((f)*(RW-RB)/CR)+RB)+.5);
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return (c > 255 ? 255 : c);
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}
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#define Code2V(c, RB, RW, CR) ((((c)-(int)RB)*(float)CR)/(float)(RW-RB))
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#define CLAMP(f,min,max) \
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(int)((f)+.5 < (min) ? (min) : (f)+.5 > (max) ? (max) : (f)+.5)
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static
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void
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check(int R, int G, int B)
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{
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float Y, Cb, Cr;
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int iY, iCb, iCr;
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float rY, rCb, rCr;
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float rR, rG, rB;
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int eR, eG, eB;
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Y = lumaRed[R] + lumaGreen[G] + lumaBlue[B];
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Cb = (B - Y)*D2;
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Cr = (R - Y)*D1;
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iY = V2Code(Y, refBlackWhite[0], refBlackWhite[1], 255);
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iCb = V2Code(Cb, refBlackWhite[2], refBlackWhite[3], 127);
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iCr = V2Code(Cr, refBlackWhite[4], refBlackWhite[5], 127);
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rCb = Code2V(iCb, refBlackWhite[2], refBlackWhite[3], 127);
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rCr = Code2V(iCr, refBlackWhite[4], refBlackWhite[5], 127);
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rY = Code2V(iY, refBlackWhite[0], refBlackWhite[1], 255);
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rR = rY + rCr*D3;
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rB = rY + rCb*D4;
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rG = rY - rCb*D6 - rCr*D5;
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eR = R - CLAMP(rR,0,255);
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eG = G - CLAMP(rG,0,255);
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eB = B - CLAMP(rB,0,255);
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if (abs(eR) > 1 || abs(eG) > 1 || abs(eB) > 1) {
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printf("R %u G %u B %u", R, G, B);
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printf(" Y %g Cb %g Cr %g", Y, Cb, Cr);
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printf(" iY %u iCb %u iCr %u", iY, iCb, iCr);
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printf("\n -> Y %g Cb %g Cr %g", rY, rCb, rCr);
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printf(" R %g (%u) G %g (%u) B %g (%u) E=[%d %d %d])\n"
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, rR, CLAMP(rR,0,255)
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, rG, CLAMP(rG,0,255)
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, rB, CLAMP(rB,0,255)
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, eR, eG, eB
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);
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}
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eRtotal += eR;
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eGtotal += eG;
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eBtotal += eB;
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AbseRtotal += abs(eR);
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AbseGtotal += abs(eG);
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AbseBtotal += abs(eB);
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if (eR | eG | eB)
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eCodes++;
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eBits += abs(eR) + abs(eG) + abs(eB);
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}
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/*
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* Local Variables:
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* mode: c
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* c-basic-offset: 8
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* fill-column: 78
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* End:
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*/
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