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/* $Header: /cvsroot/osrs/libtiff/libtiff/tif_color.c,v 1.7 2003/12/24 22:02:04 dron Exp $ */
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* Copyright (c) 1988-1997 Sam Leffler
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* Copyright (c) 1991-1997 Silicon Graphics, Inc.
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* Permission to use, copy, modify, distribute, and sell this software and
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* its documentation for any purpose is hereby granted without fee, provided
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* that (i) the above copyright notices and this permission notice appear in
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* all copies of the software and related documentation, and (ii) the names of
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* Sam Leffler and Silicon Graphics may not be used in any advertising or
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* publicity relating to the software without the specific, prior written
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* permission of Sam Leffler and Silicon Graphics.
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* THE SOFTWARE IS PROVIDED "AS-IS" AND WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS, IMPLIED OR OTHERWISE, INCLUDING WITHOUT LIMITATION, ANY
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* WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
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* IN NO EVENT SHALL SAM LEFFLER OR SILICON GRAPHICS BE LIABLE FOR
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* ANY SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND,
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* OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
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* WHETHER OR NOT ADVISED OF THE POSSIBILITY OF DAMAGE, AND ON ANY THEORY OF
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* LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
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* CIE L*a*b* to CIE XYZ and CIE XYZ to RGB conversion routines are taken
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* from the VIPS library (http://www.vips.ecs.soton.ac.uk) with
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* the permission of John Cupitt, the VIPS author.
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* Color space conversion routines.
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* Convert color value from the CIE L*a*b* 1976 space to CIE XYZ.
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TIFFCIELabToXYZ(TIFFCIELabToRGB *cielab, uint32 l, int32 a, int32 b,
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float *X, float *Y, float *Z)
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float L = (float)l * 100.0F / 255.0F;
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*Y = (L * cielab->Y0) / 903.292F;
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cby = 7.787F * (*Y / cielab->Y0) + 16.0F / 116.0F;
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cby = (L + 16.0F) / 116.0F;
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*Y = cielab->Y0 * cby * cby * cby;
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tmp = (float)a / 500.0F + cby;
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*X = cielab->X0 * (tmp - 0.13793F) / 7.787F;
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*X = cielab->X0 * tmp * tmp * tmp;
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tmp = cby - (float)b / 200.0F;
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*Z = cielab->Z0 * (tmp - 0.13793F) / 7.787F;
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*Z = cielab->Z0 * tmp * tmp * tmp;
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#define RINT(R) ((uint32)((R)>0?((R)+0.5):((R)-0.5)))
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* Convert color value from the XYZ space to RGB.
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TIFFXYZToRGB(TIFFCIELabToRGB *cielab, float X, float Y, float Z,
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uint32 *r, uint32 *g, uint32 *b)
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float *matrix = &cielab->display.d_mat[0][0];
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/* Multiply through the matrix to get luminosity values. */
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Yr = matrix[0] * X + matrix[1] * Y + matrix[2] * Z;
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Yg = matrix[3] * X + matrix[4] * Y + matrix[5] * Z;
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Yb = matrix[6] * X + matrix[7] * Y + matrix[8] * Z;
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Yr = TIFFmax( Yr, cielab->display.d_Y0R );
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Yg = TIFFmax( Yg, cielab->display.d_Y0G );
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Yb = TIFFmax( Yb, cielab->display.d_Y0B );
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/* Turn luminosity to colour value. */
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i = TIFFmin(cielab->range,
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(int)((Yr - cielab->display.d_Y0R) / cielab->rstep));
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*r = RINT(cielab->Yr2r[i]);
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i = TIFFmin(cielab->range,
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(int)((Yg - cielab->display.d_Y0G) / cielab->gstep));
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*g = RINT(cielab->Yg2g[i]);
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i = TIFFmin(cielab->range,
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(int)((Yb - cielab->display.d_Y0B) / cielab->bstep));
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*b = RINT(cielab->Yb2b[i]);
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*r = TIFFmin( *r, cielab->display.d_Vrwr );
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*g = TIFFmin( *g, cielab->display.d_Vrwg );
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*b = TIFFmin( *b, cielab->display.d_Vrwb );
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* Allocate conversion state structures and make look_up tables for
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* the Yr,Yb,Yg <=> r,g,b conversions.
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TIFFCIELabToRGBInit(TIFFCIELabToRGB* cielab,
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TIFFDisplay *display, float *refWhite)
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cielab->range = CIELABTORGB_TABLE_RANGE;
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_TIFFmemcpy(&cielab->display, display, sizeof(TIFFDisplay));
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gamma = 1.0F / cielab->display.d_gammaR ;
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(cielab->display.d_YCR - cielab->display.d_Y0R) / cielab->range;
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for(i = 0; i <= cielab->range; i++) {
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cielab->Yr2r[i] = cielab->display.d_Vrwr
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* ((float)pow((double)i / cielab->range, gamma));
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gamma = 1.0F / cielab->display.d_gammaG ;
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(cielab->display.d_YCR - cielab->display.d_Y0R) / cielab->range;
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for(i = 0; i <= cielab->range; i++) {
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cielab->Yg2g[i] = cielab->display.d_Vrwg
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* ((float)pow((double)i / cielab->range, gamma));
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gamma = 1.0F / cielab->display.d_gammaB ;
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(cielab->display.d_YCR - cielab->display.d_Y0R) / cielab->range;
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for(i = 0; i <= cielab->range; i++) {
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cielab->Yb2b[i] = cielab->display.d_Vrwb
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* ((float)pow((double)i / cielab->range, gamma));
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/* Init reference white point */
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cielab->X0 = refWhite[0];
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cielab->Y0 = refWhite[1];
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cielab->Z0 = refWhite[2];
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* Convert color value from the YCbCr space to CIE XYZ.
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* The colorspace conversion algorithm comes from the IJG v5a code;
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* see below for more information on how it works.
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#define FIX(x) ((int32)((x) * (1L<<SHIFT) + 0.5))
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#define ONE_HALF ((int32)(1<<(SHIFT-1)))
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#define Code2V(c, RB, RW, CR) ((((c)-(int32)(RB))*(float)(CR))/(float)((RW)-(RB)))
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#define CLAMP(f,min,max) ((f)<(min)?(min):(f)>(max)?(max):(f))
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TIFFYCbCrtoRGB(TIFFYCbCrToRGB *ycbcr, uint32 Y, int32 Cb, int32 Cr,
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uint32 *r, uint32 *g, uint32 *b)
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/* XXX: Only 8-bit YCbCr input supported for now */
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Y = CLAMP(Y, 0, 255), Cb = CLAMP(Cb, 0, 255), Cr = CLAMP(Cr, 0, 255);
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*r = ycbcr->clamptab[ycbcr->Y_tab[Y] + ycbcr->Cr_r_tab[Cr]];
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*g = ycbcr->clamptab[ycbcr->Y_tab[Y]
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+ (int)((ycbcr->Cb_g_tab[Cb] + ycbcr->Cr_g_tab[Cr]) >> SHIFT)];
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*b = ycbcr->clamptab[ycbcr->Y_tab[Y] + ycbcr->Cb_b_tab[Cb]];
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* Initialize the YCbCr->RGB conversion tables. The conversion
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* is done according to the 6.0 spec:
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* R = Y + Cr*(2 - 2*LumaRed)
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* B = Y + Cb*(2 - 2*LumaBlue)
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* - LumaBlue*Cb*(2-2*LumaBlue)/LumaGreen
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* - LumaRed*Cr*(2-2*LumaRed)/LumaGreen
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* To avoid floating point arithmetic the fractional constants that
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* come out of the equations are represented as fixed point values
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* in the range 0...2^16. We also eliminate multiplications by
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* pre-calculating possible values indexed by Cb and Cr (this code
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* assumes conversion is being done for 8-bit samples).
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TIFFYCbCrToRGBInit(TIFFYCbCrToRGB* ycbcr, float *luma, float *refBlackWhite)
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TIFFRGBValue* clamptab;
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#define LumaRed luma[0]
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#define LumaGreen luma[1]
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#define LumaBlue luma[2]
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clamptab = (TIFFRGBValue*)(
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(tidata_t) ycbcr+TIFFroundup(sizeof (TIFFYCbCrToRGB), sizeof (long)));
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_TIFFmemset(clamptab, 0, 256); /* v < 0 => 0 */
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ycbcr->clamptab = (clamptab += 256);
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for (i = 0; i < 256; i++)
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clamptab[i] = (TIFFRGBValue) i;
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_TIFFmemset(clamptab+256, 255, 2*256); /* v > 255 => 255 */
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ycbcr->Cr_r_tab = (int*) (clamptab + 3*256);
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ycbcr->Cb_b_tab = ycbcr->Cr_r_tab + 256;
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ycbcr->Cr_g_tab = (int32*) (ycbcr->Cb_b_tab + 256);
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ycbcr->Cb_g_tab = ycbcr->Cr_g_tab + 256;
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ycbcr->Y_tab = ycbcr->Cb_g_tab + 256;
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{ float f1 = 2-2*LumaRed; int32 D1 = FIX(f1);
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float f2 = LumaRed*f1/LumaGreen; int32 D2 = -FIX(f2);
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float f3 = 2-2*LumaBlue; int32 D3 = FIX(f3);
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float f4 = LumaBlue*f3/LumaGreen; int32 D4 = -FIX(f4);
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* i is the actual input pixel value in the range 0..255
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* Cb and Cr values are in the range -128..127 (actually
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* they are in a range defined by the ReferenceBlackWhite
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* tag) so there is some range shifting to do here when
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* constructing tables indexed by the raw pixel data.
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for (i = 0, x = -128; i < 256; i++, x++) {
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int32 Cr = (int32)Code2V(x, refBlackWhite[4] - 128.0F,
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refBlackWhite[5] - 128.0F, 127);
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int32 Cb = (int32)Code2V(x, refBlackWhite[2] - 128.0F,
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refBlackWhite[3] - 128.0F, 127);
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ycbcr->Cr_r_tab[i] = (int32)((D1*Cr + ONE_HALF)>>SHIFT);
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ycbcr->Cb_b_tab[i] = (int32)((D3*Cb + ONE_HALF)>>SHIFT);
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ycbcr->Cr_g_tab[i] = D2*Cr;
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ycbcr->Cb_g_tab[i] = D4*Cb + ONE_HALF;
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(int32)Code2V(x + 128, refBlackWhite[0], refBlackWhite[1], 255);
added
removed
libtiff/tif_color.c
