    /*
     * jccolor.c
     *
     * Copyright (C) 1991-1996, Thomas G. Lane.
     * Modified 2011-2019 by Guido Vollbeding.
     * This file is part of the Independent JPEG Group's software.
     * For conditions of distribution and use, see the accompanying README file.
     *
     * This file contains input colorspace conversion routines.
     */

    #define JPEG_INTERNALS
    #include "jinclude.h"
    #include "jpeglib.h"

    /* Private subobject */

    typedef struct {
      struct jpeg_color_converter pub; /* public fields */

      /* Private state for RGB->YCC conversion */
      INT32 * rgb_ycc_tab;		/* => table for RGB to YCbCr conversion */
    } my_color_converter;

    typedef my_color_converter * my_cconvert_ptr;

    /**************** RGB -> YCbCr conversion: most common case **************/

    /*
     * YCbCr is defined per Recommendation ITU-R BT.601-7 (03/2011),
     * previously known as Recommendation CCIR 601-1, except that Cb and Cr
     * are normalized to the range 0..MAXJSAMPLE rather than -0.5 .. 0.5.
     * sRGB (standard RGB color space) is defined per IEC 61966-2-1:1999.
     * sYCC (standard luma-chroma-chroma color space with extended gamut)
     * is defined per IEC 61966-2-1:1999 Amendment A1:2003 Annex F.
     * bg-sRGB and bg-sYCC (big gamut standard color spaces)
     * are defined per IEC 61966-2-1:1999 Amendment A1:2003 Annex G.
     * Note that the derived conversion coefficients given in some of these
     * documents are imprecise.  The general conversion equations are
     *	Y  = Kr * R + (1 - Kr - Kb) * G + Kb * B
     *	Cb = 0.5 * (B - Y) / (1 - Kb)
     *	Cr = 0.5 * (R - Y) / (1 - Kr)
     * With Kr = 0.299 and Kb = 0.114 (derived according to SMPTE RP 177-1993
     * from the 1953 FCC NTSC primaries and CIE Illuminant C),
     * the conversion equations to be implemented are therefore
     *	Y  =  0.299 * R + 0.587 * G + 0.114 * B
     *	Cb = -0.168735892 * R - 0.331264108 * G + 0.5 * B + CENTERJSAMPLE
     *	Cr =  0.5 * R - 0.418687589 * G - 0.081312411 * B + CENTERJSAMPLE
     * Note: older versions of the IJG code used a zero offset of MAXJSAMPLE/2,
     * rather than CENTERJSAMPLE, for Cb and Cr.  This gave equal positive and
     * negative swings for Cb/Cr, but meant that grayscale values (Cb=Cr=0)
     * were not represented exactly.  Now we sacrifice exact representation of
     * maximum red and maximum blue in order to get exact grayscales.
     *
     * To avoid floating-point arithmetic, we represent the fractional constants
     * as integers scaled up by 2^16 (about 4 digits precision); we have to divide
     * the products by 2^16, with appropriate rounding, to get the correct answer.
     *
     * For even more speed, we avoid doing any multiplications in the inner loop
     * by precalculating the constants times R,G,B for all possible values.
     * For 8-bit JSAMPLEs this is very reasonable (only 256 entries per table);
     * for 9-bit to 12-bit samples it is still acceptable.  It's not very
     * reasonable for 16-bit samples, but if you want lossless storage you
     * shouldn't be changing colorspace anyway.
     * The CENTERJSAMPLE offsets and the rounding fudge-factor of 0.5 are included
     * in the tables to save adding them separately in the inner loop.
     */

    #define SCALEBITS	16	/* speediest right-shift on some machines */
    #define CBCR_OFFSET	((INT32) CENTERJSAMPLE << SCALEBITS)
    #define ONE_HALF	((INT32) 1 << (SCALEBITS-1))
    #define FIX(x)		((INT32) ((x) * (1L<<SCALEBITS) + 0.5))

    /* We allocate one big table and divide it up into eight parts, instead of
     * doing eight alloc_small requests.  This lets us use a single table base
     * address, which can be held in a register in the inner loops on many
     * machines (more than can hold all eight addresses, anyway).
     */

    #define R_Y_OFF		0			/* offset to R => Y section */
    #define G_Y_OFF		(1*(MAXJSAMPLE+1))	/* offset to G => Y section */
    #define B_Y_OFF		(2*(MAXJSAMPLE+1))	/* etc. */
    #define R_CB_OFF	(3*(MAXJSAMPLE+1))
    #define G_CB_OFF	(4*(MAXJSAMPLE+1))
    #define B_CB_OFF	(5*(MAXJSAMPLE+1))
    #define R_CR_OFF	B_CB_OFF		/* B=>Cb, R=>Cr are the same */
    #define G_CR_OFF	(6*(MAXJSAMPLE+1))
    #define B_CR_OFF	(7*(MAXJSAMPLE+1))
    #define TABLE_SIZE	(8*(MAXJSAMPLE+1))

    /*
     * Initialize for RGB->YCC colorspace conversion.
     */

    METHODDEF(void)
    rgb_ycc_start (j_compress_ptr cinfo)
    {
      my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
      INT32 * rgb_ycc_tab;
      INT32 i;

      /* Allocate and fill in the conversion tables. */
      cconvert->rgb_ycc_tab = rgb_ycc_tab = (INT32 *)
        (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
    				TABLE_SIZE * SIZEOF(INT32));

      for (i = 0; i <= MAXJSAMPLE; i++) {
        rgb_ycc_tab[i+R_Y_OFF] = FIX(0.299) * i;
        rgb_ycc_tab[i+G_Y_OFF] = FIX(0.587) * i;
        rgb_ycc_tab[i+B_Y_OFF] = FIX(0.114) * i   + ONE_HALF;
        rgb_ycc_tab[i+R_CB_OFF] = (- FIX(0.168735892)) * i;
        rgb_ycc_tab[i+G_CB_OFF] = (- FIX(0.331264108)) * i;
        /* We use a rounding fudge-factor of 0.5-epsilon for Cb and Cr.
         * This ensures that the maximum output will round to MAXJSAMPLE
         * not MAXJSAMPLE+1, and thus that we don't have to range-limit.
         */
        rgb_ycc_tab[i+B_CB_OFF] = FIX(0.5) * i    + CBCR_OFFSET + ONE_HALF-1;
    /*  B=>Cb and R=>Cr tables are the same
        rgb_ycc_tab[i+R_CR_OFF] = FIX(0.5) * i    + CBCR_OFFSET + ONE_HALF-1;
    */
        rgb_ycc_tab[i+G_CR_OFF] = (- FIX(0.418687589)) * i;
        rgb_ycc_tab[i+B_CR_OFF] = (- FIX(0.081312411)) * i;
      }
    }

    /*
     * Convert some rows of samples to the JPEG colorspace.
     *
     * Note that we change from the application's interleaved-pixel format
     * to our internal noninterleaved, one-plane-per-component format.  The
     * input buffer is therefore three times as wide as the output buffer.
     *
     * A starting row offset is provided only for the output buffer.  The
     * caller can easily adjust the passed input_buf value to accommodate
     * any row offset required on that side.
     */

    METHODDEF(void)
    rgb_ycc_convert (j_compress_ptr cinfo,
    		 JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
    		 JDIMENSION output_row, int num_rows)
    {
      my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
      register int r, g, b;
      register INT32 * ctab = cconvert->rgb_ycc_tab;
      register JSAMPROW inptr;
      register JSAMPROW outptr0, outptr1, outptr2;
      register JDIMENSION col;
      JDIMENSION num_cols = cinfo->image_width;

      while (--num_rows >= 0) {
        inptr = *input_buf++;
        outptr0 = output_buf[0][output_row];
        outptr1 = output_buf[1][output_row];
        outptr2 = output_buf[2][output_row];
        output_row++;
        for (col = 0; col < num_cols; col++) {
          r = GETJSAMPLE(inptr[RGB_RED]);
          g = GETJSAMPLE(inptr[RGB_GREEN]);
          b = GETJSAMPLE(inptr[RGB_BLUE]);
          inptr += RGB_PIXELSIZE;
          /* If the inputs are 0..MAXJSAMPLE, the outputs of these equations
           * must be too; we do not need an explicit range-limiting operation.
           * Hence the value being shifted is never negative, and we don't
           * need the general RIGHT_SHIFT macro.
           */
          /* Y */
          outptr0[col] = (JSAMPLE)
    		((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF])
    		 >> SCALEBITS);
          /* Cb */
          outptr1[col] = (JSAMPLE)
    		((ctab[r+R_CB_OFF] + ctab[g+G_CB_OFF] + ctab[b+B_CB_OFF])
    		 >> SCALEBITS);
          /* Cr */
          outptr2[col] = (JSAMPLE)
    		((ctab[r+R_CR_OFF] + ctab[g+G_CR_OFF] + ctab[b+B_CR_OFF])
    		 >> SCALEBITS);
        }
      }
    }

    /**************** Cases other than RGB -> YCbCr **************/

    /*
     * Convert some rows of samples to the JPEG colorspace.
     * This version handles RGB->grayscale conversion, which is the same
     * as the RGB->Y portion of RGB->YCbCr.
     * We assume rgb_ycc_start has been called (we only use the Y tables).
     */

    METHODDEF(void)
    rgb_gray_convert (j_compress_ptr cinfo,
    		  JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
    		  JDIMENSION output_row, int num_rows)
    {
      my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
      register int r, g, b;
      register INT32 * ctab = cconvert->rgb_ycc_tab;
      register JSAMPROW inptr;
      register JSAMPROW outptr;
      register JDIMENSION col;
      JDIMENSION num_cols = cinfo->image_width;

      while (--num_rows >= 0) {
        inptr = *input_buf++;
        outptr = output_buf[0][output_row++];
        for (col = 0; col < num_cols; col++) {
          r = GETJSAMPLE(inptr[RGB_RED]);
          g = GETJSAMPLE(inptr[RGB_GREEN]);
          b = GETJSAMPLE(inptr[RGB_BLUE]);
          inptr += RGB_PIXELSIZE;
          /* Y */
          outptr[col] = (JSAMPLE)
    		((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF])
    		 >> SCALEBITS);
        }
      }
    }

    /*
     * Convert some rows of samples to the JPEG colorspace.
     * This version handles Adobe-style CMYK->YCCK conversion,
     * where we convert R=1-C, G=1-M, and B=1-Y to YCbCr using the
     * same conversion as above, while passing K (black) unchanged.
     * We assume rgb_ycc_start has been called.
     */

    METHODDEF(void)
    cmyk_ycck_convert (j_compress_ptr cinfo,
    		   JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
    		   JDIMENSION output_row, int num_rows)
    {
      my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
      register int r, g, b;
      register INT32 * ctab = cconvert->rgb_ycc_tab;
      register JSAMPROW inptr;
      register JSAMPROW outptr0, outptr1, outptr2, outptr3;
      register JDIMENSION col;
      JDIMENSION num_cols = cinfo->image_width;

      while (--num_rows >= 0) {
        inptr = *input_buf++;
        outptr0 = output_buf[0][output_row];
        outptr1 = output_buf[1][output_row];
        outptr2 = output_buf[2][output_row];
        outptr3 = output_buf[3][output_row];
        output_row++;
        for (col = 0; col < num_cols; col++) {
          r = MAXJSAMPLE - GETJSAMPLE(inptr[0]);
          g = MAXJSAMPLE - GETJSAMPLE(inptr[1]);
          b = MAXJSAMPLE - GETJSAMPLE(inptr[2]);
          /* K passes through as-is */
          outptr3[col] = inptr[3];	/* don't need GETJSAMPLE here */
          inptr += 4;
          /* If the inputs are 0..MAXJSAMPLE, the outputs of these equations
           * must be too; we do not need an explicit range-limiting operation.
           * Hence the value being shifted is never negative, and we don't
           * need the general RIGHT_SHIFT macro.
           */
          /* Y */
          outptr0[col] = (JSAMPLE)
    		((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF])
    		 >> SCALEBITS);
          /* Cb */
          outptr1[col] = (JSAMPLE)
    		((ctab[r+R_CB_OFF] + ctab[g+G_CB_OFF] + ctab[b+B_CB_OFF])
    		 >> SCALEBITS);
          /* Cr */
          outptr2[col] = (JSAMPLE)
    		((ctab[r+R_CR_OFF] + ctab[g+G_CR_OFF] + ctab[b+B_CR_OFF])
    		 >> SCALEBITS);
        }
      }
    }

    /*
     * Convert some rows of samples to the JPEG colorspace.
     * [R,G,B] to [R-G,G,B-G] conversion with modulo calculation
     * (forward reversible color transform).
     * This can be seen as an adaption of the general RGB->YCbCr
     * conversion equation with Kr = Kb = 0, while replacing the
     * normalization by modulo calculation.
     */

    METHODDEF(void)
    rgb_rgb1_convert (j_compress_ptr cinfo,
    		  JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
    		  JDIMENSION output_row, int num_rows)
    {
      register int r, g, b;
      register JSAMPROW inptr;
      register JSAMPROW outptr0, outptr1, outptr2;
      register JDIMENSION col;
      JDIMENSION num_cols = cinfo->image_width;

      while (--num_rows >= 0) {
        inptr = *input_buf++;
        outptr0 = output_buf[0][output_row];
        outptr1 = output_buf[1][output_row];
        outptr2 = output_buf[2][output_row];
        output_row++;
        for (col = 0; col < num_cols; col++) {
          r = GETJSAMPLE(inptr[RGB_RED]);
          g = GETJSAMPLE(inptr[RGB_GREEN]);
          b = GETJSAMPLE(inptr[RGB_BLUE]);
          inptr += RGB_PIXELSIZE;
          /* Assume that MAXJSAMPLE+1 is a power of 2, so that the MOD
           * (modulo) operator is equivalent to the bitmask operator AND.
           */
          outptr0[col] = (JSAMPLE) ((r - g + CENTERJSAMPLE) & MAXJSAMPLE);
          outptr1[col] = (JSAMPLE) g;
          outptr2[col] = (JSAMPLE) ((b - g + CENTERJSAMPLE) & MAXJSAMPLE);
        }
      }
    }

    /*
     * Convert some rows of samples to the JPEG colorspace.
     * This version handles grayscale output with no conversion.
     * The source can be either plain grayscale or YCC (since Y == gray).
     */

    METHODDEF(void)
    grayscale_convert (j_compress_ptr cinfo,
    		   JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
    		   JDIMENSION output_row, int num_rows)
    {
      register JSAMPROW inptr;
      register JSAMPROW outptr;
      register JDIMENSION count;
      register int instride = cinfo->input_components;
      JDIMENSION num_cols = cinfo->image_width;

      while (--num_rows >= 0) {
        inptr = *input_buf++;
        outptr = output_buf[0][output_row++];
        for (count = num_cols; count > 0; count--) {
          *outptr++ = *inptr;	/* don't need GETJSAMPLE() here */
          inptr += instride;
        }
      }
    }

    /*
     * Convert some rows of samples to the JPEG colorspace.
     * No colorspace conversion, but change from interleaved
     * to separate-planes representation.
     */

    METHODDEF(void)
    rgb_convert (j_compress_ptr cinfo,
    	     JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
    	     JDIMENSION output_row, int num_rows)
    {
      register JSAMPROW inptr;
      register JSAMPROW outptr0, outptr1, outptr2;
      register JDIMENSION col;
      JDIMENSION num_cols = cinfo->image_width;

      while (--num_rows >= 0) {
        inptr = *input_buf++;
        outptr0 = output_buf[0][output_row];
        outptr1 = output_buf[1][output_row];
        outptr2 = output_buf[2][output_row];
        output_row++;
        for (col = 0; col < num_cols; col++) {
          /* We can dispense with GETJSAMPLE() here */
          outptr0[col] = inptr[RGB_RED];
          outptr1[col] = inptr[RGB_GREEN];
          outptr2[col] = inptr[RGB_BLUE];
          inptr += RGB_PIXELSIZE;
        }
      }
    }

    /*
     * Convert some rows of samples to the JPEG colorspace.
     * This version handles multi-component colorspaces without conversion.
     * We assume input_components == num_components.
     */

    METHODDEF(void)
    null_convert (j_compress_ptr cinfo,
    	      JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
    	      JDIMENSION output_row, int num_rows)
    {
      register JSAMPROW inptr;
      register JSAMPROW outptr;
      register JDIMENSION count;
      register int num_comps = cinfo->num_components;
      JDIMENSION num_cols = cinfo->image_width;
      int ci;

      while (--num_rows >= 0) {
        /* It seems fastest to make a separate pass for each component. */
        for (ci = 0; ci < num_comps; ci++) {
          inptr = input_buf[0] + ci;
          outptr = output_buf[ci][output_row];
          for (count = num_cols; count > 0; count--) {
    	*outptr++ = *inptr;	/* don't need GETJSAMPLE() here */
    	inptr += num_comps;
          }
        }
        input_buf++;
        output_row++;
      }
    }

    /*
     * Empty method for start_pass.
     */

    METHODDEF(void)
    null_method (j_compress_ptr cinfo)
    {
      /* no work needed */
    }

    /*
     * Module initialization routine for input colorspace conversion.
     */

    GLOBAL(void)
    jinit_color_converter (j_compress_ptr cinfo)
    {
      my_cconvert_ptr cconvert;

      cconvert = (my_cconvert_ptr) (*cinfo->mem->alloc_small)
        ((j_common_ptr) cinfo, JPOOL_IMAGE, SIZEOF(my_color_converter));
      cinfo->cconvert = &cconvert->pub;
      /* set start_pass to null method until we find out differently */
      cconvert->pub.start_pass = null_method;

      /* Make sure input_components agrees with in_color_space */
      switch (cinfo->in_color_space) {
      case JCS_GRAYSCALE:
        if (cinfo->input_components != 1)
          ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
        break;

      case JCS_RGB:
      case JCS_BG_RGB:
    #if RGB_PIXELSIZE != 3
        if (cinfo->input_components != RGB_PIXELSIZE)
          ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
        break;
    #endif /* else share code with YCbCr */

      case JCS_YCbCr:
      case JCS_BG_YCC:
        if (cinfo->input_components != 3)
          ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
        break;

      case JCS_CMYK:
      case JCS_YCCK:
        if (cinfo->input_components != 4)
          ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
        break;

      default:			/* JCS_UNKNOWN can be anything */
        if (cinfo->input_components < 1)
          ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
      }

      /* Support color transform only for RGB colorspaces */
      if (cinfo->color_transform &&
          cinfo->jpeg_color_space != JCS_RGB &&
          cinfo->jpeg_color_space != JCS_BG_RGB)
        ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);

      /* Check num_components, set conversion method based on requested space */
      switch (cinfo->jpeg_color_space) {
      case JCS_GRAYSCALE:
        if (cinfo->num_components != 1)
          ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
        switch (cinfo->in_color_space) {
        case JCS_GRAYSCALE:
        case JCS_YCbCr:
        case JCS_BG_YCC:
          cconvert->pub.color_convert = grayscale_convert;
          break;
        case JCS_RGB:
          cconvert->pub.start_pass = rgb_ycc_start;
          cconvert->pub.color_convert = rgb_gray_convert;
          break;
        default:
          ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
        }
        break;

      case JCS_RGB:
      case JCS_BG_RGB:
        if (cinfo->num_components != 3)
          ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
        if (cinfo->in_color_space != cinfo->jpeg_color_space)
          ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
        switch (cinfo->color_transform) {
        case JCT_NONE:
          cconvert->pub.color_convert = rgb_convert;
          break;
        case JCT_SUBTRACT_GREEN:
          cconvert->pub.color_convert = rgb_rgb1_convert;
          break;
        default:
          ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
        }
        break;

      case JCS_YCbCr:
        if (cinfo->num_components != 3)
          ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
        switch (cinfo->in_color_space) {
        case JCS_RGB:
          cconvert->pub.start_pass = rgb_ycc_start;
          cconvert->pub.color_convert = rgb_ycc_convert;
          break;
        case JCS_YCbCr:
          cconvert->pub.color_convert = null_convert;
          break;
        default:
          ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
        }
        break;

      case JCS_BG_YCC:
        if (cinfo->num_components != 3)
          ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
        switch (cinfo->in_color_space) {
        case JCS_RGB:
          /* For conversion from normal RGB input to BG_YCC representation,
           * the Cb/Cr values are first computed as usual, and then
           * quantized further after DCT processing by a factor of
           * 2 in reference to the nominal quantization factor.
           */
          /* need quantization scale by factor of 2 after DCT */
          cinfo->comp_info[1].component_needed = TRUE;
          cinfo->comp_info[2].component_needed = TRUE;
          /* compute normal YCC first */
          cconvert->pub.start_pass = rgb_ycc_start;
          cconvert->pub.color_convert = rgb_ycc_convert;
          break;
        case JCS_YCbCr:
          /* need quantization scale by factor of 2 after DCT */
          cinfo->comp_info[1].component_needed = TRUE;
          cinfo->comp_info[2].component_needed = TRUE;
          /*FALLTHROUGH*/
        case JCS_BG_YCC:
          /* Pass through for BG_YCC input */
          cconvert->pub.color_convert = null_convert;
          break;
        default:
          ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
        }
        break;

      case JCS_CMYK:
        if (cinfo->num_components != 4)
          ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
        if (cinfo->in_color_space != JCS_CMYK)
          ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
        cconvert->pub.color_convert = null_convert;
        break;

      case JCS_YCCK:
        if (cinfo->num_components != 4)
          ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
        switch (cinfo->in_color_space) {
        case JCS_CMYK:
          cconvert->pub.start_pass = rgb_ycc_start;
          cconvert->pub.color_convert = cmyk_ycck_convert;
          break;
        case JCS_YCCK:
          cconvert->pub.color_convert = null_convert;
          break;
        default:
          ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
        }
        break;

      default:			/* allow null conversion of JCS_UNKNOWN */
        if (cinfo->jpeg_color_space != cinfo->in_color_space ||
    	cinfo->num_components != cinfo->input_components)
          ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
        cconvert->pub.color_convert = null_convert;
      }
    }