text: /*
   * 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 "jinclude8.h"
  #include "jpeglib8.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 */
    IJG_INT32 * Cr_g_tab;		/* => table for Cr to G conversion */
    IJG_INT32 * 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	((IJG_INT32) 1 << (SCALEBITS-1))
  #define FIX(x)		((IJG_INT32) ((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;
    IJG_INT32 x;
  #if BITS_IN_JSAMPLE == 16
    /* no need for temporaries */
  #else
    SHIFT_TEMPS
  #endif
  
    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 = (IJG_INT32 *)
      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
  				(MAXJSAMPLE+1) * SIZEOF(IJG_INT32));
    cconvert->Cb_g_tab = (IJG_INT32 *)
      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
  				(MAXJSAMPLE+1) * SIZEOF(IJG_INT32));
  
    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 */
  
  #if BITS_IN_JSAMPLE == 16
      /* Bug fix 2001-11-06 by Eichelberg: The integer routines below
         produce an overflow when used with MAXJSAMPLE == 65535.
         Use floating point calculation instead. */
  
      /* Cr=>R value is nearest int to 1.40200 * x */
      cconvert->Cr_r_tab[i] = (int)(1.40200 * (double)x + 0.5);
      /* Cb=>B value is nearest int to 1.77200 * x */
      cconvert->Cb_b_tab[i] = (int)(1.77200 * (double)x + 0.5);
  #else
      /* 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);
  #endif
  
      /* 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;
    register int y, cb, cr;
    register JSAMPROW outptr;
    register JSAMPROW inptr0, inptr1, inptr2;
    register JDIMENSION col;
    JDIMENSION num_cols = cinfo->output_width;
    /* copy these pointers into registers if possible */
    register JSAMPLE * range_limit = cinfo->sample_range_limit;
    register int * Crrtab = cconvert->Cr_r_tab;
    register int * Cbbtab = cconvert->Cb_b_tab;
    register IJG_INT32 * Crgtab = cconvert->Cr_g_tab;
    register IJG_INT32 * 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)
  {
    register JSAMPROW inptr, outptr;
    register JDIMENSION count;
    register 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)
  {
    register JSAMPROW inptr, outptr;
    register 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;
    register int y, cb, cr;
    register JSAMPROW outptr;
    register JSAMPROW inptr0, inptr1, inptr2, inptr3;
    register JDIMENSION col;
    JDIMENSION num_cols = cinfo->output_width;
    /* copy these pointers into registers if possible */
    register JSAMPLE * range_limit = cinfo->sample_range_limit;
    register int * Crrtab = cconvert->Cr_r_tab;
    register int * Cbbtab = cconvert->Cb_b_tab;
    register IJG_INT32 * Crgtab = cconvert->Cr_g_tab;
    register IJG_INT32 * 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 cinfo)
  {
    (void)cinfo;
    /* 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;
  }
  