    /*
     * jdcolor.c
     *
     * Copyright (C) 1991-1997, Thomas G. Lane.
     * 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 output colorspace conversion routines.
     */

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

    /* Private subobject */

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

      /* Private state for YCC->RGB conversion */
      int * Cr_r_tab;		/* => table for Cr to R conversion */
      int * Cb_b_tab;		/* => table for Cb to B conversion */
      long * Cr_g_tab;		/* => table for Cr to G conversion */
      long * Cb_g_tab;		/* => table for Cb to G conversion */
    } my_color_deconverter;

    typedef my_color_deconverter * my_cconvert_ptr;

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

    /*
     * YCbCr is defined per CCIR 601-1, except that Cb and Cr are
     * normalized to the range 0..MAXJSAMPLE rather than -0.5 .. 0.5.
     * The conversion equations to be implemented are therefore
     *	R = Y                + 1.40200 * Cr
     *	G = Y - 0.34414 * Cb - 0.71414 * Cr
     *	B = Y + 1.77200 * Cb
     * where Cb and Cr represent the incoming values less CENTERJSAMPLE.
     * (These numbers are derived from TIFF 6.0 section 21, dated 3-June-92.)
     *
     * 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.
     * Notice that Y, being an integral input, does not contribute any fraction
     * so it need not participate in the rounding.
     *
     * For even more speed, we avoid doing any multiplications in the inner loop
     * by precalculating the constants times Cb and Cr for all possible values.
     * For 8-bit JSAMPLEs this is very reasonable (only 256 entries per table);
     * for 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 Cr=>R and Cb=>B values can be rounded to integers in advance; the
     * values for the G calculation are left scaled up, since we must add them
     * together before rounding.
     */

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

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

    LOCAL(void)
    build_ycc_rgb_table (j_decompress_ptr cinfo)
    {
      my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
      int i;
      long x;
      SHIFT_TEMPS

      cconvert->Cr_r_tab = (int *)
        (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
    				(MAXJSAMPLE+1) * SIZEOF(int));
      cconvert->Cb_b_tab = (int *)
        (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
    				(MAXJSAMPLE+1) * SIZEOF(int));
      cconvert->Cr_g_tab = (long *)
        (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
    				(MAXJSAMPLE+1) * SIZEOF(long));
      cconvert->Cb_g_tab = (long *)
        (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
    				(MAXJSAMPLE+1) * SIZEOF(long));

      for (i = 0, x = -CENTERJSAMPLE; i <= MAXJSAMPLE; i++, x++) {
        /* i is the actual input pixel value, in the range 0..MAXJSAMPLE */
        /* The Cb or Cr value we are thinking of is x = i - CENTERJSAMPLE */
        /* Cr=>R value is nearest int to 1.40200 * x */
        cconvert->Cr_r_tab[i] = (int)
    		    RIGHT_SHIFT(FIX(1.40200) * x + ONE_HALF, SCALEBITS);
        /* Cb=>B value is nearest int to 1.77200 * x */
        cconvert->Cb_b_tab[i] = (int)
    		    RIGHT_SHIFT(FIX(1.77200) * x + ONE_HALF, SCALEBITS);
        /* Cr=>G value is scaled-up -0.71414 * x */
        cconvert->Cr_g_tab[i] = (- FIX(0.71414)) * x;
        /* Cb=>G value is scaled-up -0.34414 * x */
        /* We also add in ONE_HALF so that need not do it in inner loop */
        cconvert->Cb_g_tab[i] = (- FIX(0.34414)) * x + ONE_HALF;
      }
    }

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

    METHODDEF(void)
    ycc_rgb_convert (j_decompress_ptr cinfo,
    		 JSAMPIMAGE input_buf, JDIMENSION input_row,
    		 JSAMPARRAY output_buf, int num_rows)
    {
      my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
      int y, cb, cr;
      JSAMPROW outptr;
      JSAMPROW inptr0, inptr1, inptr2;
      JDIMENSION col;
      JDIMENSION num_cols = cinfo->output_width;
      /* copy these pointers into registers if possible */
      JSAMPLE * range_limit = cinfo->sample_range_limit;
      int * Crrtab = cconvert->Cr_r_tab;
      int * Cbbtab = cconvert->Cb_b_tab;
      long * Crgtab = cconvert->Cr_g_tab;
      long * Cbgtab = cconvert->Cb_g_tab;
      SHIFT_TEMPS

      while (--num_rows >= 0) {
        inptr0 = input_buf[0][input_row];
        inptr1 = input_buf[1][input_row];
        inptr2 = input_buf[2][input_row];
        input_row++;
        outptr = *output_buf++;
        for (col = 0; col < num_cols; col++) {
          y  = GETJSAMPLE(inptr0[col]);
          cb = GETJSAMPLE(inptr1[col]);
          cr = GETJSAMPLE(inptr2[col]);
          /* Range-limiting is essential due to noise introduced by DCT losses. */
          outptr[RGB_RED] =   range_limit[y + Crrtab[cr]];
          outptr[RGB_GREEN] = range_limit[y +
    			      ((int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr],
    						 SCALEBITS))];
          outptr[RGB_BLUE] =  range_limit[y + Cbbtab[cb]];
          outptr += RGB_PIXELSIZE;
        }
      }
    }

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

    /*
     * Color conversion for no colorspace change: just copy the data,
     * converting from separate-planes to interleaved representation.
     */

    METHODDEF(void)
    null_convert (j_decompress_ptr cinfo,
    	      JSAMPIMAGE input_buf, JDIMENSION input_row,
    	      JSAMPARRAY output_buf, int num_rows)
    {
      JSAMPROW inptr, outptr;
      JDIMENSION count;
      int num_components = cinfo->num_components;
      JDIMENSION num_cols = cinfo->output_width;
      int ci;

      while (--num_rows >= 0) {
        for (ci = 0; ci < num_components; ci++) {
          inptr = input_buf[ci][input_row];
          outptr = output_buf[0] + ci;
          for (count = num_cols; count > 0; count--) {
    	*outptr = *inptr++;	/* needn't bother with GETJSAMPLE() here */
    	outptr += num_components;
          }
        }
        input_row++;
        output_buf++;
      }
    }

    /*
     * Color conversion for grayscale: just copy the data.
     * This also works for YCbCr -> grayscale conversion, in which
     * we just copy the Y (luminance) component and ignore chrominance.
     */

    METHODDEF(void)
    grayscale_convert (j_decompress_ptr cinfo,
    		   JSAMPIMAGE input_buf, JDIMENSION input_row,
    		   JSAMPARRAY output_buf, int num_rows)
    {
      jcopy_sample_rows(input_buf[0], (int) input_row, output_buf, 0,
    		    num_rows, cinfo->output_width);
    }

    /*
     * Convert grayscale to RGB: just duplicate the graylevel three times.
     * This is provided to support applications that don't want to cope
     * with grayscale as a separate case.
     */

    METHODDEF(void)
    gray_rgb_convert (j_decompress_ptr cinfo,
    		  JSAMPIMAGE input_buf, JDIMENSION input_row,
    		  JSAMPARRAY output_buf, int num_rows)
    {
      JSAMPROW inptr, outptr;
      JDIMENSION col;
      JDIMENSION num_cols = cinfo->output_width;

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

    /*
     * Adobe-style YCCK->CMYK conversion.
     * We convert YCbCr to R=1-C, G=1-M, and B=1-Y using the same
     * conversion as above, while passing K (black) unchanged.
     * We assume build_ycc_rgb_table has been called.
     */

    METHODDEF(void)
    ycck_cmyk_convert (j_decompress_ptr cinfo,
    		   JSAMPIMAGE input_buf, JDIMENSION input_row,
    		   JSAMPARRAY output_buf, int num_rows)
    {
      my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
      int y, cb, cr;
      JSAMPROW outptr;
      JSAMPROW inptr0, inptr1, inptr2, inptr3;
      JDIMENSION col;
      JDIMENSION num_cols = cinfo->output_width;
      /* copy these pointers into registers if possible */
      JSAMPLE * range_limit = cinfo->sample_range_limit;
      int * Crrtab = cconvert->Cr_r_tab;
      int * Cbbtab = cconvert->Cb_b_tab;
      long * Crgtab = cconvert->Cr_g_tab;
      long * Cbgtab = cconvert->Cb_g_tab;
      SHIFT_TEMPS

      while (--num_rows >= 0) {
        inptr0 = input_buf[0][input_row];
        inptr1 = input_buf[1][input_row];
        inptr2 = input_buf[2][input_row];
        inptr3 = input_buf[3][input_row];
        input_row++;
        outptr = *output_buf++;
        for (col = 0; col < num_cols; col++) {
          y  = GETJSAMPLE(inptr0[col]);
          cb = GETJSAMPLE(inptr1[col]);
          cr = GETJSAMPLE(inptr2[col]);
          /* Range-limiting is essential due to noise introduced by DCT losses. */
          outptr[0] = range_limit[MAXJSAMPLE - (y + Crrtab[cr])];	/* red */
          outptr[1] = range_limit[MAXJSAMPLE - (y +			/* green */
    			      ((int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr],
    						 SCALEBITS)))];
          outptr[2] = range_limit[MAXJSAMPLE - (y + Cbbtab[cb])];	/* blue */
          /* K passes through unchanged */
          outptr[3] = inptr3[col];	/* don't need GETJSAMPLE here */
          outptr += 4;
        }
      }
    }

    /*
     * Empty method for start_pass.
     */

    METHODDEF(void)
    start_pass_dcolor (j_decompress_ptr )
    {
      /* no work needed */
    }

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

    GLOBAL(void)
    jinit_color_deconverter (j_decompress_ptr cinfo)
    {
      my_cconvert_ptr cconvert;
      int ci;

      cconvert = (my_cconvert_ptr)
        (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
    				SIZEOF(my_color_deconverter));
      cinfo->cconvert = (struct jpeg_color_deconverter *) cconvert;
      cconvert->pub.start_pass = start_pass_dcolor;

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

      case JCS_RGB:
      case JCS_YCbCr:
        if (cinfo->num_components != 3)
          ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
        break;

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

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

      /* Set out_color_components and conversion method based on requested space.
       * Also clear the component_needed flags for any unused components,
       * so that earlier pipeline stages can avoid useless computation.
       */

      switch (cinfo->out_color_space) {
      case JCS_GRAYSCALE:
        cinfo->out_color_components = 1;
        if (cinfo->jpeg_color_space == JCS_GRAYSCALE ||
    	cinfo->jpeg_color_space == JCS_YCbCr) {
          cconvert->pub.color_convert = grayscale_convert;
          /* For color->grayscale conversion, only the Y (0) component is needed */
          for (ci = 1; ci < cinfo->num_components; ci++)
    	cinfo->comp_info[ci].component_needed = FALSE;
        } else
          ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
        break;

      case JCS_RGB:
        cinfo->out_color_components = RGB_PIXELSIZE;
        if (cinfo->jpeg_color_space == JCS_YCbCr) {
          cconvert->pub.color_convert = ycc_rgb_convert;
          build_ycc_rgb_table(cinfo);
        } else if (cinfo->jpeg_color_space == JCS_GRAYSCALE) {
          cconvert->pub.color_convert = gray_rgb_convert;
        } else if (cinfo->jpeg_color_space == JCS_RGB && RGB_PIXELSIZE == 3) {
          cconvert->pub.color_convert = null_convert;
        } else
          ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
        break;

      case JCS_CMYK:
        cinfo->out_color_components = 4;
        if (cinfo->jpeg_color_space == JCS_YCCK) {
          cconvert->pub.color_convert = ycck_cmyk_convert;
          build_ycc_rgb_table(cinfo);
        } else if (cinfo->jpeg_color_space == JCS_CMYK) {
          cconvert->pub.color_convert = null_convert;
        } else
          ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
        break;

      default:
        /* Permit null conversion to same output space */
        if (cinfo->out_color_space == cinfo->jpeg_color_space) {
          cinfo->out_color_components = cinfo->num_components;
          cconvert->pub.color_convert = null_convert;
        } else			/* unsupported non-null conversion */
          ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
        break;
      }

      if (cinfo->quantize_colors)
        cinfo->output_components = 1; /* single colormapped output component */
      else
        cinfo->output_components = cinfo->out_color_components;
    }