tif_color.c

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/*
 * Copyright (c) 1988-1997 Sam Leffler
 * Copyright (c) 1991-1997 Silicon Graphics, Inc.
 *
 * Permission to use, copy, modify, distribute, and sell this software and 
 * its documentation for any purpose is hereby granted without fee, provided
 * that (i) the above copyright notices and this permission notice appear in
 * all copies of the software and related documentation, and (ii) the names of
 * Sam Leffler and Silicon Graphics may not be used in any advertising or
 * publicity relating to the software without the specific, prior written
 * permission of Sam Leffler and Silicon Graphics.
 * 
 * THE SOFTWARE IS PROVIDED "AS-IS" AND WITHOUT WARRANTY OF ANY KIND, 
 * EXPRESS, IMPLIED OR OTHERWISE, INCLUDING WITHOUT LIMITATION, ANY 
 * WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.  
 * 
 * IN NO EVENT SHALL SAM LEFFLER OR SILICON GRAPHICS BE LIABLE FOR
 * ANY SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND,
 * OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
 * WHETHER OR NOT ADVISED OF THE POSSIBILITY OF DAMAGE, AND ON ANY THEORY OF 
 * LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE 
 * OF THIS SOFTWARE.
 */

/*
 * CIE L*a*b* to CIE XYZ and CIE XYZ to RGB conversion routines are taken
 * from the VIPS library (http://www.vips.ecs.soton.ac.uk) with
 * the permission of John Cupitt, the VIPS author.
 */

/*
 * TIFF Library.
 *
 * Color space conversion routines.
 */

#include <precomp.h>
#include <math.h>

/*
 * Convert color value from the CIE L*a*b* 1976 space to CIE XYZ.
 */
void
TIFFCIELabToXYZ(TIFFCIELabToRGB *cielab, uint32 l, int32 a, int32 b,
        float *X, float *Y, float *Z)
{
    float L = (float)l * 100.0F / 255.0F;
    float cby, tmp;

    if( L < 8.856F ) {
        *Y = (L * cielab->Y0) / 903.292F;
        cby = 7.787F * (*Y / cielab->Y0) + 16.0F / 116.0F;
    } else {
        cby = (L + 16.0F) / 116.0F;
        *Y = cielab->Y0 * cby * cby * cby;
    }

    tmp = (float)a / 500.0F + cby;
    if( tmp < 0.2069F )
        *X = cielab->X0 * (tmp - 0.13793F) / 7.787F;
    else    
        *X = cielab->X0 * tmp * tmp * tmp;

    tmp = cby - (float)b / 200.0F;
    if( tmp < 0.2069F )
        *Z = cielab->Z0 * (tmp - 0.13793F) / 7.787F;
    else    
        *Z = cielab->Z0 * tmp * tmp * tmp;
}

#define RINT(R) ((uint32)((R)>0?((R)+0.5):((R)-0.5)))
/*
 * Convert color value from the XYZ space to RGB.
 */
void
TIFFXYZToRGB(TIFFCIELabToRGB *cielab, float X, float Y, float Z,
         uint32 *r, uint32 *g, uint32 *b)
{
    int i;
    float Yr, Yg, Yb;
    float *matrix = &cielab->display.d_mat[0][0];

    /* Multiply through the matrix to get luminosity values. */
    Yr =  matrix[0] * X + matrix[1] * Y + matrix[2] * Z;
    Yg =  matrix[3] * X + matrix[4] * Y + matrix[5] * Z;
    Yb =  matrix[6] * X + matrix[7] * Y + matrix[8] * Z;

    /* Clip input */
    Yr = TIFFmax(Yr, cielab->display.d_Y0R);
    Yg = TIFFmax(Yg, cielab->display.d_Y0G);
    Yb = TIFFmax(Yb, cielab->display.d_Y0B);

    /* Avoid overflow in case of wrong input values */
    Yr = TIFFmin(Yr, cielab->display.d_YCR);
    Yg = TIFFmin(Yg, cielab->display.d_YCG);
    Yb = TIFFmin(Yb, cielab->display.d_YCB);

    /* Turn luminosity to colour value. */
    i = (int)((Yr - cielab->display.d_Y0R) / cielab->rstep);
    i = TIFFmin(cielab->range, i);
    *r = RINT(cielab->Yr2r[i]);

    i = (int)((Yg - cielab->display.d_Y0G) / cielab->gstep);
    i = TIFFmin(cielab->range, i);
    *g = RINT(cielab->Yg2g[i]);

    i = (int)((Yb - cielab->display.d_Y0B) / cielab->bstep);
    i = TIFFmin(cielab->range, i);
    *b = RINT(cielab->Yb2b[i]);

    /* Clip output. */
    *r = TIFFmin(*r, cielab->display.d_Vrwr);
    *g = TIFFmin(*g, cielab->display.d_Vrwg);
    *b = TIFFmin(*b, cielab->display.d_Vrwb);
}
#undef RINT

/* 
 * Allocate conversion state structures and make look_up tables for
 * the Yr,Yb,Yg <=> r,g,b conversions.
 */
int
TIFFCIELabToRGBInit(TIFFCIELabToRGB* cielab,
            const TIFFDisplay *display, float *refWhite)
{
    int i;
    double dfGamma;

    cielab->range = CIELABTORGB_TABLE_RANGE;

    _TIFFmemcpy(&cielab->display, display, sizeof(TIFFDisplay));

    /* Red */
    dfGamma = 1.0 / cielab->display.d_gammaR ;
    cielab->rstep =
        (cielab->display.d_YCR - cielab->display.d_Y0R) / cielab->range;
    for(i = 0; i <= cielab->range; i++) {
        cielab->Yr2r[i] = cielab->display.d_Vrwr
            * ((float)pow((double)i / cielab->range, dfGamma));
    }

    /* Green */
    dfGamma = 1.0 / cielab->display.d_gammaG ;
    cielab->gstep =
        (cielab->display.d_YCR - cielab->display.d_Y0R) / cielab->range;
    for(i = 0; i <= cielab->range; i++) {
        cielab->Yg2g[i] = cielab->display.d_Vrwg
            * ((float)pow((double)i / cielab->range, dfGamma));
    }

    /* Blue */
    dfGamma = 1.0 / cielab->display.d_gammaB ;
    cielab->bstep =
        (cielab->display.d_YCR - cielab->display.d_Y0R) / cielab->range;
    for(i = 0; i <= cielab->range; i++) {
        cielab->Yb2b[i] = cielab->display.d_Vrwb
            * ((float)pow((double)i / cielab->range, dfGamma));
    }

    /* Init reference white point */
    cielab->X0 = refWhite[0];
    cielab->Y0 = refWhite[1];
    cielab->Z0 = refWhite[2];

    return 0;
}

/* 
 * Convert color value from the YCbCr space to RGB.
 * The colorspace conversion algorithm comes from the IJG v5a code;
 * see below for more information on how it works.
 */
#define SHIFT           16
#define FIX(x)          ((int32)((x) * (1L<<SHIFT) + 0.5))
#define ONE_HALF        ((int32)(1<<(SHIFT-1)))
#define Code2V(c, RB, RW, CR)   ((((c)-(int32)(RB))*(float)(CR))/(float)(((RW)-(RB)!=0) ? ((RW)-(RB)) : 1))
#define CLAMP(f,min,max)    ((f)<(min)?(min):(f)>(max)?(max):(f))
#define HICLAMP(f,max)      ((f)>(max)?(max):(f))

void
TIFFYCbCrtoRGB(TIFFYCbCrToRGB *ycbcr, uint32 Y, int32 Cb, int32 Cr,
           uint32 *r, uint32 *g, uint32 *b)
{
    int32 i;

    /* XXX: Only 8-bit YCbCr input supported for now */
    Y = HICLAMP(Y, 255);
    Cb = CLAMP(Cb, 0, 255);
    Cr = CLAMP(Cr, 0, 255);

    i = ycbcr->Y_tab[Y] + ycbcr->Cr_r_tab[Cr];
    *r = CLAMP(i, 0, 255);
    i = ycbcr->Y_tab[Y]
        + (int)((ycbcr->Cb_g_tab[Cb] + ycbcr->Cr_g_tab[Cr]) >> SHIFT);
    *g = CLAMP(i, 0, 255);
    i = ycbcr->Y_tab[Y] + ycbcr->Cb_b_tab[Cb];
    *b = CLAMP(i, 0, 255);
}

/* Clamp function for sanitization purposes. Normally clamping should not */
/* occur for well behaved chroma and refBlackWhite coefficients */
static float CLAMPw(float v, float vmin, float vmax)
{
    if( v < vmin )
    {
        /* printf("%f clamped to %f\n", v, vmin); */
        return vmin;
    }
    if( v > vmax )
    {
        /* printf("%f clamped to %f\n", v, vmax); */
        return vmax;
    }
    return v;
}

/*
 * Initialize the YCbCr->RGB conversion tables.  The conversion
 * is done according to the 6.0 spec:
 *
 *    R = Y + Cr*(2 - 2*LumaRed)
 *    B = Y + Cb*(2 - 2*LumaBlue)
 *    G =   Y
 *        - LumaBlue*Cb*(2-2*LumaBlue)/LumaGreen
 *        - LumaRed*Cr*(2-2*LumaRed)/LumaGreen
 *
 * To avoid floating point arithmetic the fractional constants that
 * come out of the equations are represented as fixed point values
 * in the range 0...2^16.  We also eliminate multiplications by
 * pre-calculating possible values indexed by Cb and Cr (this code
 * assumes conversion is being done for 8-bit samples).
 */
int
TIFFYCbCrToRGBInit(TIFFYCbCrToRGB* ycbcr, float *luma, float *refBlackWhite)
{
    TIFFRGBValue* clamptab;
    int i;
    
#define LumaRed     luma[0]
#define LumaGreen   luma[1]
#define LumaBlue    luma[2]

    clamptab = (TIFFRGBValue*)(
    (uint8*) ycbcr+TIFFroundup_32(sizeof (TIFFYCbCrToRGB), sizeof (long)));  
    _TIFFmemset(clamptab, 0, 256);      /* v < 0 => 0 */
    ycbcr->clamptab = (clamptab += 256);
    for (i = 0; i < 256; i++)
    clamptab[i] = (TIFFRGBValue) i;
    _TIFFmemset(clamptab+256, 255, 2*256);  /* v > 255 => 255 */
    ycbcr->Cr_r_tab = (int*) (clamptab + 3*256);
    ycbcr->Cb_b_tab = ycbcr->Cr_r_tab + 256;
    ycbcr->Cr_g_tab = (int32*) (ycbcr->Cb_b_tab + 256);
    ycbcr->Cb_g_tab = ycbcr->Cr_g_tab + 256;
    ycbcr->Y_tab = ycbcr->Cb_g_tab + 256;

    { float f1 = 2-2*LumaRed;       int32 D1 = FIX(CLAMP(f1,0.0F,2.0F));
      float f2 = LumaRed*f1/LumaGreen;  int32 D2 = -FIX(CLAMP(f2,0.0F,2.0F));
      float f3 = 2-2*LumaBlue;      int32 D3 = FIX(CLAMP(f3,0.0F,2.0F));
      float f4 = LumaBlue*f3/LumaGreen; int32 D4 = -FIX(CLAMP(f4,0.0F,2.0F));
      int x;

#undef LumaBlue
#undef LumaGreen
#undef LumaRed
      
      /*
       * i is the actual input pixel value in the range 0..255
       * Cb and Cr values are in the range -128..127 (actually
       * they are in a range defined by the ReferenceBlackWhite
       * tag) so there is some range shifting to do here when
       * constructing tables indexed by the raw pixel data.
       */
      for (i = 0, x = -128; i < 256; i++, x++) {
        int32 Cr = (int32)CLAMPw(Code2V(x, refBlackWhite[4] - 128.0F,
                refBlackWhite[5] - 128.0F, 127),
                            -128.0F * 32, 128.0F * 32);
        int32 Cb = (int32)CLAMPw(Code2V(x, refBlackWhite[2] - 128.0F,
                refBlackWhite[3] - 128.0F, 127),
                            -128.0F * 32, 128.0F * 32);

        ycbcr->Cr_r_tab[i] = (int32)((D1*Cr + ONE_HALF)>>SHIFT);
        ycbcr->Cb_b_tab[i] = (int32)((D3*Cb + ONE_HALF)>>SHIFT);
        ycbcr->Cr_g_tab[i] = D2*Cr;
        ycbcr->Cb_g_tab[i] = D4*Cb + ONE_HALF;
        ycbcr->Y_tab[i] =
            (int32)CLAMPw(Code2V(x + 128, refBlackWhite[0], refBlackWhite[1], 255),
                                  -128.0F * 32, 128.0F * 32);
      }
    }

    return 0;
}
#undef  HICLAMP
#undef  CLAMP
#undef  Code2V
#undef  SHIFT
#undef  ONE_HALF
#undef  FIX

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 * End:
 */