jdcolor.c - third_party/libjpeg-turbo - Git at Google

 /*
  * jdcolor.c
  *
  * Copyright (C) 1991-1995, 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 */
   INT32 * Cr_g_tab;		/* => table for Cr to G conversion */
   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	((INT32) 1 << (SCALEBITS-1))
 #define FIX(x)		((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;
   INT32 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 = (INT32 *)
     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 				(MAXJSAMPLE+1) * SIZEOF(INT32));
   cconvert->Cb_g_tab = (INT32 *)
     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 				(MAXJSAMPLE+1) * SIZEOF(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 */
     /* 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;
   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 INT32 * Crgtab = cconvert->Cr_g_tab;
   register 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);
 }


 /*
  * 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 INT32 * Crgtab = cconvert->Cr_g_tab;
   register 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)
 {
   /* 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_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;
 }
	/*
	* jdcolor.c
	*
	* Copyright (C) 1991-1995, 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 */
	INT32 * Cr_g_tab; /* => table for Cr to G conversion */
	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 ((INT32) 1 << (SCALEBITS-1))
	#define FIX(x) ((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;
	INT32 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 = (INT32 *)
	(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
	(MAXJSAMPLE+1) * SIZEOF(INT32));
	cconvert->Cb_g_tab = (INT32 *)
	(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
	(MAXJSAMPLE+1) * SIZEOF(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 */
	/* 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;
	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 INT32 * Crgtab = cconvert->Cr_g_tab;
	register 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);
	}


	/*
	* 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 INT32 * Crgtab = cconvert->Cr_g_tab;
	register 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)
	{
	/* 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_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;
	}