/* Id */

/*
 * 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 "tiffiop.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,
                    TIFFDisplay *display, float *refWhite)
{
        int i;
        double gamma2;

        cielab->range = CIELABTORGB_TABLE_RANGE;

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

        /* Red */
        gamma2 = 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, gamma2));
        }

        /* Green */
        gamma2 = 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, gamma2));
        }

        /* Blue */
        gamma2 = 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, gamma2));
        }

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

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

/*
 * 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*)(
        (tidata_t) ycbcr+TIFFroundup(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(f1);
      float f2 = LumaRed*f1/LumaGreen;  int32 D2 = -FIX(f2);
      float f3 = 2-2*LumaBlue;          int32 D3 = FIX(f3);
      float f4 = LumaBlue*f3/LumaGreen; int32 D4 = -FIX(f4);
      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)Code2V(x, refBlackWhite[4] - 128.0F,
                            refBlackWhite[5] - 128.0F, 127);
            int32 Cb = (int32)Code2V(x, refBlackWhite[2] - 128.0F,
                            refBlackWhite[3] - 128.0F, 127);

            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)Code2V(x + 128, refBlackWhite[0], refBlackWhite[1], 255);
      }
    }

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

/* vim: set ts=8 sts=8 sw=8 noet: */
