1 files changed, 168 insertions, 0 deletions
diff --git a/tiff/tools/ycbcr.c b/tiff/tools/ycbcr.c
new file mode 100644
index 0000000..8f72447
--- /dev/null
+++ b/tiff/tools/ycbcr.c
@@ -0,0 +1,168 @@
+float	ycbcrCoeffs[3] = { .299, .587, .114 };
+/* default coding range is CCIR Rec 601-1 with no headroom/footroom */
+unsigned long refBlackWhite[6] = { 0, 255, 128, 255, 128, 255 };
+
+#define	LumaRed		ycbcrCoeffs[0]
+#define	LumaGreen	ycbcrCoeffs[1]
+#define	LumaBlue	ycbcrCoeffs[2]
+
+long	eRtotal = 0;
+long	eGtotal = 0;
+long	eBtotal = 0;
+long	preveRtotal = 0;
+long	preveGtotal = 0;
+long	preveBtotal = 0;
+unsigned long AbseRtotal = 0;
+unsigned long AbseGtotal = 0;
+unsigned long AbseBtotal = 0;
+unsigned long eCodes = 0;
+unsigned long preveCodes = 0;
+unsigned long eBits = 0;
+unsigned long preveBits = 0;
+
+static	void setupLumaTables();
+static int abs(int v) { return (v < 0 ? -v : v); }
+static double pct(int v,double range) { return (v*100. / range); }
+static void check(int R, int G, int B);
+
+float	D1, D2;
+float	D3, D4;
+float	D5, D6;
+
+int
+main(int argc, char** argv)
+{
+    int R, G, B;
+
+    if (argc > 1) {
+	refBlackWhite[0] = 16;
+	refBlackWhite[1] = 235;
+	refBlackWhite[2] = 128;
+	refBlackWhite[3] = 240;
+	refBlackWhite[4] = 128;
+	refBlackWhite[5] = 240;
+    }
+    D3 = 2 - 2*LumaRed;
+    D4 = 2 - 2*LumaBlue;
+    D1 = 1. / D3;
+    D2 = 1. / D4;
+    D5 = D3*LumaRed / LumaGreen;
+    D6 = D4*LumaBlue / LumaGreen;
+    setupLumaTables();
+    for (R = 0; R < 256; R++) {
+	for (G = 0; G < 256; G++)
+	    for (B = 0; B < 256; B++)
+		check(R, G, B);
+	printf("[%3u] c %u/%u b %u/%u (R %u/%d/%u G %u/%d/%u B %u/%d/%u)\n"
+	    , R
+	    , eCodes - preveCodes, eCodes
+	    , eBits - preveBits, eBits
+	    , abs(AbseRtotal - preveRtotal), eRtotal , AbseRtotal
+	    , abs(AbseGtotal - preveGtotal), eGtotal , AbseGtotal
+	    , abs(AbseBtotal - preveBtotal), eBtotal , AbseBtotal
+	);
+	preveRtotal = AbseRtotal;
+	preveGtotal = AbseGtotal;
+	preveBtotal = AbseBtotal;
+	preveCodes = eCodes;
+	preveBits = eBits;
+    }
+    printf("%u total codes\n", 256*256*256);
+    printf("total error: %u codes %u bits (R %d/%u G %d/%u B %d/%u)\n"
+	, eCodes
+	, eBits
+	, eRtotal , AbseRtotal
+	, eGtotal , AbseGtotal
+	, eBtotal , AbseBtotal
+    );
+    return (0);
+}
+
+float	*lumaRed;
+float	*lumaGreen;
+float	*lumaBlue;
+
+static float*
+setupLuma(float c)
+{
+    float *v = (float *)_TIFFmalloc(256 * sizeof (float));
+    int i;
+    for (i = 0; i < 256; i++)
+	v[i] = c * i;
+    return (v);
+}
+
+static void
+setupLumaTables(void)
+{
+    lumaRed = setupLuma(LumaRed);
+    lumaGreen = setupLuma(LumaGreen);
+    lumaBlue = setupLuma(LumaBlue);
+}
+
+static unsigned
+V2Code(float f, unsigned long RB, unsigned long RW, int CR)
+{
+    unsigned int c = (unsigned int)((((f)*(RW-RB)/CR)+RB)+.5);
+    return (c > 255 ? 255 : c);
+}
+
+#define	Code2V(c, RB, RW, CR)	((((c)-(int)RB)*(float)CR)/(float)(RW-RB))
+
+#define	CLAMP(f,min,max) \
+    (int)((f)+.5 < (min) ? (min) : (f)+.5 > (max) ? (max) : (f)+.5)
+
+static
+void
+check(int R, int G, int B)
+{
+    float Y, Cb, Cr;
+    int iY, iCb, iCr;
+    float rY, rCb, rCr;
+    float rR, rG, rB;
+    int eR, eG, eB;
+
+    Y = lumaRed[R] + lumaGreen[G] + lumaBlue[B];
+    Cb = (B - Y)*D2;
+    Cr = (R - Y)*D1;
+    iY = V2Code(Y, refBlackWhite[0], refBlackWhite[1], 255);
+    iCb = V2Code(Cb, refBlackWhite[2], refBlackWhite[3], 127);
+    iCr = V2Code(Cr, refBlackWhite[4], refBlackWhite[5], 127);
+    rCb = Code2V(iCb, refBlackWhite[2], refBlackWhite[3], 127);
+    rCr = Code2V(iCr, refBlackWhite[4], refBlackWhite[5], 127);
+    rY = Code2V(iY, refBlackWhite[0], refBlackWhite[1], 255);
+    rR = rY + rCr*D3;
+    rB = rY + rCb*D4;
+    rG = rY - rCb*D6 - rCr*D5;
+    eR = R - CLAMP(rR,0,255);
+    eG = G - CLAMP(rG,0,255);
+    eB = B - CLAMP(rB,0,255);
+    if (abs(eR) > 1 || abs(eG) > 1 || abs(eB) > 1) {
+	printf("R %u G %u B %u", R, G, B);
+	printf(" Y %g Cb %g Cr %g", Y, Cb, Cr);
+	printf(" iY %u iCb %u iCr %u", iY, iCb, iCr);
+	printf("\n -> Y %g Cb %g Cr %g", rY, rCb, rCr);
+	printf(" R %g (%u) G %g (%u) B %g (%u) E=[%d %d %d])\n"
+	    , rR, CLAMP(rR,0,255)
+	    , rG, CLAMP(rG,0,255)
+	    , rB, CLAMP(rB,0,255)
+	    , eR, eG, eB
+	);
+    }
+    eRtotal += eR;
+    eGtotal += eG;
+    eBtotal += eB;
+    AbseRtotal += abs(eR);
+    AbseGtotal += abs(eG);
+    AbseBtotal += abs(eB);
+    if (eR | eG | eB)
+	eCodes++;
+    eBits += abs(eR) + abs(eG) + abs(eB);
+}
+/*
+ * Local Variables:
+ * mode: c
+ * c-basic-offset: 8
+ * fill-column: 78
+ * End:
+ */