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();
abs(int v)24 static int abs(int v) { return (v < 0 ? -v : v); }
pct(int v,double range)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
main(int argc,char ** argv)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*
setupLuma(float c)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
setupLumaTables(void)96 setupLumaTables(void)
97 {
98 lumaRed = setupLuma(LumaRed);
99 lumaGreen = setupLuma(LumaGreen);
100 lumaBlue = setupLuma(LumaBlue);
101 }
102
103 static unsigned
V2Code(float f,unsigned long RB,unsigned long RW,int CR)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
check(int R,int G,int B)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 */
169