jccolor.c - external/github.com/libjpeg-turbo/libjpeg-turbo - Git at Google

 /*
  * jccolor.c
  *
  * Copyright (C) 1991, 1992, 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 input colorspace conversion routines.
  * These routines are invoked via the methods get_sample_rows
  * and colorin_init/term.
  */

 #include "jinclude.h"


 static JSAMPARRAY pixel_row;	/* Workspace for a pixel row in input format */


 /**************** RGB -> YCbCr 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
  *	Y  =  0.29900 * R + 0.58700 * G + 0.11400 * B
  *	Cb = -0.16874 * R - 0.33126 * G + 0.50000 * B  + MAXJSAMPLE/2
  *	Cr =  0.50000 * R - 0.41869 * G - 0.08131 * B  + MAXJSAMPLE/2
  * (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.
  *
  * 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 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 MAXJSAMPLE/2 offsets and the rounding fudge-factor of 0.5 are included
  * in the tables to save adding them separately in the inner loop.
  */

 #ifdef SIXTEEN_BIT_SAMPLES
 #define SCALEBITS	14	/* avoid overflow */
 #else
 #define SCALEBITS	16	/* speedier right-shift on some machines */
 #endif
 #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).
  */

 static INT32 * rgb_ycc_tab;	/* => table for RGB to YCbCr conversion */
 #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 colorspace conversion.
  */

 METHODDEF void
 rgb_ycc_init (compress_info_ptr cinfo)
 {
   INT32 i;

   /* Allocate a workspace for the result of get_input_row. */
   pixel_row = (*cinfo->emethods->alloc_small_sarray)
 		(cinfo->image_width, (long) cinfo->input_components);

   /* Allocate and fill in the conversion tables. */
   rgb_ycc_tab = (INT32 *) (*cinfo->emethods->alloc_small)
 				(TABLE_SIZE * SIZEOF(INT32));

   for (i = 0; i <= MAXJSAMPLE; i++) {
     rgb_ycc_tab[i+R_Y_OFF] = FIX(0.29900) * i;
     rgb_ycc_tab[i+G_Y_OFF] = FIX(0.58700) * i;
     rgb_ycc_tab[i+B_Y_OFF] = FIX(0.11400) * i     + ONE_HALF;
     rgb_ycc_tab[i+R_CB_OFF] = (-FIX(0.16874)) * i;
     rgb_ycc_tab[i+G_CB_OFF] = (-FIX(0.33126)) * i;
     rgb_ycc_tab[i+B_CB_OFF] = FIX(0.50000) * i    + ONE_HALF*(MAXJSAMPLE+1);
 /*  B=>Cb and R=>Cr tables are the same
     rgb_ycc_tab[i+R_CR_OFF] = FIX(0.50000) * i    + ONE_HALF*(MAXJSAMPLE+1);
 */
     rgb_ycc_tab[i+G_CR_OFF] = (-FIX(0.41869)) * i;
     rgb_ycc_tab[i+B_CR_OFF] = (-FIX(0.08131)) * i;
   }
 }


 /*
  * Fetch some rows of pixels from get_input_row and convert to the
  * JPEG colorspace.
  */

 METHODDEF void
 get_rgb_ycc_rows (compress_info_ptr cinfo,
 		  int rows_to_read, JSAMPIMAGE image_data)
 {
 #ifdef SIXTEEN_BIT_SAMPLES
   register UINT16 r, g, b;
 #else
   register int r, g, b;
 #endif
   register INT32 * ctab = rgb_ycc_tab;
   register JSAMPROW inptr0, inptr1, inptr2;
   register JSAMPROW outptr0, outptr1, outptr2;
   register long col;
   long width = cinfo->image_width;
   int row;

   for (row = 0; row < rows_to_read; row++) {
     /* Read one row from the source file */
     (*cinfo->methods->get_input_row) (cinfo, pixel_row);
     /* Convert colorspace */
     inptr0 = pixel_row[0];
     inptr1 = pixel_row[1];
     inptr2 = pixel_row[2];
     outptr0 = image_data[0][row];
     outptr1 = image_data[1][row];
     outptr2 = image_data[2][row];
     for (col = 0; col < width; col++) {
       r = GETJSAMPLE(inptr0[col]);
       g = GETJSAMPLE(inptr1[col]);
       b = GETJSAMPLE(inptr2[col]);
       /* 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 **************/


 /*
  * Fetch some rows of pixels from get_input_row and convert 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_init has been called (we only use the Y tables).
  */

 METHODDEF void
 get_rgb_gray_rows (compress_info_ptr cinfo,
 		   int rows_to_read, JSAMPIMAGE image_data)
 {
 #ifdef SIXTEEN_BIT_SAMPLES
   register UINT16 r, g, b;
 #else
   register int r, g, b;
 #endif
   register INT32 * ctab = rgb_ycc_tab;
   register JSAMPROW inptr0, inptr1, inptr2;
   register JSAMPROW outptr;
   register long col;
   long width = cinfo->image_width;
   int row;

   for (row = 0; row < rows_to_read; row++) {
     /* Read one row from the source file */
     (*cinfo->methods->get_input_row) (cinfo, pixel_row);
     /* Convert colorspace */
     inptr0 = pixel_row[0];
     inptr1 = pixel_row[1];
     inptr2 = pixel_row[2];
     outptr = image_data[0][row];
     for (col = 0; col < width; col++) {
       r = GETJSAMPLE(inptr0[col]);
       g = GETJSAMPLE(inptr1[col]);
       b = GETJSAMPLE(inptr2[col]);
       /* 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 */
       outptr[col] = (JSAMPLE)
 		((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF])
 		 >> SCALEBITS);
     }
   }
 }


 /*
  * Initialize for colorspace conversion.
  */

 METHODDEF void
 colorin_init (compress_info_ptr cinfo)
 {
   /* Allocate a workspace for the result of get_input_row. */
   pixel_row = (*cinfo->emethods->alloc_small_sarray)
 		(cinfo->image_width, (long) cinfo->input_components);
 }


 /*
  * Fetch some rows of pixels from get_input_row and convert to the
  * JPEG colorspace.
  * This version handles grayscale output with no conversion.
  * The source can be either plain grayscale or YCbCr (since Y == gray).
  */

 METHODDEF void
 get_grayscale_rows (compress_info_ptr cinfo,
 		    int rows_to_read, JSAMPIMAGE image_data)
 {
   int row;

   for (row = 0; row < rows_to_read; row++) {
     /* Read one row from the source file */
     (*cinfo->methods->get_input_row) (cinfo, pixel_row);
     /* Convert colorspace (gamma mapping needed here) */
     jcopy_sample_rows(pixel_row, 0, image_data[0], row,
 		      1, cinfo->image_width);
   }
 }


 /*
  * Fetch some rows of pixels from get_input_row and convert to the
  * JPEG colorspace.
  * This version handles multi-component colorspaces without conversion.
  */

 METHODDEF void
 get_noconvert_rows (compress_info_ptr cinfo,
 		    int rows_to_read, JSAMPIMAGE image_data)
 {
   int row, ci;

   for (row = 0; row < rows_to_read; row++) {
     /* Read one row from the source file */
     (*cinfo->methods->get_input_row) (cinfo, pixel_row);
     /* Convert colorspace (gamma mapping needed here) */
     for (ci = 0; ci < cinfo->input_components; ci++) {
       jcopy_sample_rows(pixel_row, ci, image_data[ci], row,
 			1, cinfo->image_width);
     }
   }
 }


 /*
  * Finish up at the end of the file.
  */

 METHODDEF void
 colorin_term (compress_info_ptr cinfo)
 {
   /* no work (we let free_all release the workspace) */
 }


 /*
  * The method selection routine for input colorspace conversion.
  */

 GLOBAL void
 jselccolor (compress_info_ptr cinfo)
 {
   /* Make sure input_components agrees with in_color_space */
   switch (cinfo->in_color_space) {
   case CS_GRAYSCALE:
     if (cinfo->input_components != 1)
       ERREXIT(cinfo->emethods, "Bogus input colorspace");
     break;

   case CS_RGB:
   case CS_YCbCr:
   case CS_YIQ:
     if (cinfo->input_components != 3)
       ERREXIT(cinfo->emethods, "Bogus input colorspace");
     break;

   case CS_CMYK:
     if (cinfo->input_components != 4)
       ERREXIT(cinfo->emethods, "Bogus input colorspace");
     break;

   default:
     ERREXIT(cinfo->emethods, "Unsupported input colorspace");
     break;
   }

   /* Standard init/term methods (may override below) */
   cinfo->methods->colorin_init = colorin_init;
   cinfo->methods->colorin_term = colorin_term;

   /* Check num_components, set conversion method based on requested space */
   switch (cinfo->jpeg_color_space) {
   case CS_GRAYSCALE:
     if (cinfo->num_components != 1)
       ERREXIT(cinfo->emethods, "Bogus JPEG colorspace");
     if (cinfo->in_color_space == CS_GRAYSCALE)
       cinfo->methods->get_sample_rows = get_grayscale_rows;
     else if (cinfo->in_color_space == CS_RGB) {
       cinfo->methods->colorin_init = rgb_ycc_init;
       cinfo->methods->get_sample_rows = get_rgb_gray_rows;
     } else if (cinfo->in_color_space == CS_YCbCr)
       cinfo->methods->get_sample_rows = get_grayscale_rows;
     else
       ERREXIT(cinfo->emethods, "Unsupported color conversion request");
     break;

   case CS_YCbCr:
     if (cinfo->num_components != 3)
       ERREXIT(cinfo->emethods, "Bogus JPEG colorspace");
     if (cinfo->in_color_space == CS_RGB) {
       cinfo->methods->colorin_init = rgb_ycc_init;
       cinfo->methods->get_sample_rows = get_rgb_ycc_rows;
     } else if (cinfo->in_color_space == CS_YCbCr)
       cinfo->methods->get_sample_rows = get_noconvert_rows;
     else
       ERREXIT(cinfo->emethods, "Unsupported color conversion request");
     break;

   case CS_CMYK:
     if (cinfo->num_components != 4)
       ERREXIT(cinfo->emethods, "Bogus JPEG colorspace");
     if (cinfo->in_color_space == CS_CMYK)
       cinfo->methods->get_sample_rows = get_noconvert_rows;
     else
       ERREXIT(cinfo->emethods, "Unsupported color conversion request");
     break;

   default:
     ERREXIT(cinfo->emethods, "Unsupported JPEG colorspace");
     break;
   }
 }
	/*
	* jccolor.c
	*
	* Copyright (C) 1991, 1992, 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 input colorspace conversion routines.
	* These routines are invoked via the methods get_sample_rows
	* and colorin_init/term.
	*/

	#include "jinclude.h"


	static JSAMPARRAY pixel_row; /* Workspace for a pixel row in input format */


	/************** RGB -> YCbCr 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
	* Y = 0.29900 * R + 0.58700 * G + 0.11400 * B
	* Cb = -0.16874 * R - 0.33126 * G + 0.50000 * B + MAXJSAMPLE/2
	* Cr = 0.50000 * R - 0.41869 * G - 0.08131 * B + MAXJSAMPLE/2
	* (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.
	*
	* 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 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 MAXJSAMPLE/2 offsets and the rounding fudge-factor of 0.5 are included
	* in the tables to save adding them separately in the inner loop.
	*/

	#ifdef SIXTEEN_BIT_SAMPLES
	#define SCALEBITS 14 /* avoid overflow */
	#else
	#define SCALEBITS 16 /* speedier right-shift on some machines */
	#endif
	#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).
	*/

	static INT32 * rgb_ycc_tab; /* => table for RGB to YCbCr conversion */
	#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 colorspace conversion.
	*/

	METHODDEF void
	rgb_ycc_init (compress_info_ptr cinfo)
	{
	INT32 i;

	/* Allocate a workspace for the result of get_input_row. */
	pixel_row = (*cinfo->emethods->alloc_small_sarray)
	(cinfo->image_width, (long) cinfo->input_components);

	/* Allocate and fill in the conversion tables. */
	rgb_ycc_tab = (INT32 ) (cinfo->emethods->alloc_small)
	(TABLE_SIZE * SIZEOF(INT32));

	for (i = 0; i <= MAXJSAMPLE; i++) {
	rgb_ycc_tab[i+R_Y_OFF] = FIX(0.29900) * i;
	rgb_ycc_tab[i+G_Y_OFF] = FIX(0.58700) * i;
	rgb_ycc_tab[i+B_Y_OFF] = FIX(0.11400) * i + ONE_HALF;
	rgb_ycc_tab[i+R_CB_OFF] = (-FIX(0.16874)) * i;
	rgb_ycc_tab[i+G_CB_OFF] = (-FIX(0.33126)) * i;
	rgb_ycc_tab[i+B_CB_OFF] = FIX(0.50000) * i + ONE_HALF*(MAXJSAMPLE+1);
	/* B=>Cb and R=>Cr tables are the same
	rgb_ycc_tab[i+R_CR_OFF] = FIX(0.50000) * i + ONE_HALF*(MAXJSAMPLE+1);
	*/
	rgb_ycc_tab[i+G_CR_OFF] = (-FIX(0.41869)) * i;
	rgb_ycc_tab[i+B_CR_OFF] = (-FIX(0.08131)) * i;
	}
	}


	/*
	* Fetch some rows of pixels from get_input_row and convert to the
	* JPEG colorspace.
	*/

	METHODDEF void
	get_rgb_ycc_rows (compress_info_ptr cinfo,
	int rows_to_read, JSAMPIMAGE image_data)
	{
	#ifdef SIXTEEN_BIT_SAMPLES
	register UINT16 r, g, b;
	#else
	register int r, g, b;
	#endif
	register INT32 * ctab = rgb_ycc_tab;
	register JSAMPROW inptr0, inptr1, inptr2;
	register JSAMPROW outptr0, outptr1, outptr2;
	register long col;
	long width = cinfo->image_width;
	int row;

	for (row = 0; row < rows_to_read; row++) {
	/* Read one row from the source file */
	(*cinfo->methods->get_input_row) (cinfo, pixel_row);
	/* Convert colorspace */
	inptr0 = pixel_row[0];
	inptr1 = pixel_row[1];
	inptr2 = pixel_row[2];
	outptr0 = image_data[0][row];
	outptr1 = image_data[1][row];
	outptr2 = image_data[2][row];
	for (col = 0; col < width; col++) {
	r = GETJSAMPLE(inptr0[col]);
	g = GETJSAMPLE(inptr1[col]);
	b = GETJSAMPLE(inptr2[col]);
	/* 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 ************/


	/*
	* Fetch some rows of pixels from get_input_row and convert 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_init has been called (we only use the Y tables).
	*/

	METHODDEF void
	get_rgb_gray_rows (compress_info_ptr cinfo,
	int rows_to_read, JSAMPIMAGE image_data)
	{
	#ifdef SIXTEEN_BIT_SAMPLES
	register UINT16 r, g, b;
	#else
	register int r, g, b;
	#endif
	register INT32 * ctab = rgb_ycc_tab;
	register JSAMPROW inptr0, inptr1, inptr2;
	register JSAMPROW outptr;
	register long col;
	long width = cinfo->image_width;
	int row;

	for (row = 0; row < rows_to_read; row++) {
	/* Read one row from the source file */
	(*cinfo->methods->get_input_row) (cinfo, pixel_row);
	/* Convert colorspace */
	inptr0 = pixel_row[0];
	inptr1 = pixel_row[1];
	inptr2 = pixel_row[2];
	outptr = image_data[0][row];
	for (col = 0; col < width; col++) {
	r = GETJSAMPLE(inptr0[col]);
	g = GETJSAMPLE(inptr1[col]);
	b = GETJSAMPLE(inptr2[col]);
	/* 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 */
	outptr[col] = (JSAMPLE)
	((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF])
	>> SCALEBITS);
	}
	}
	}


	/*
	* Initialize for colorspace conversion.
	*/

	METHODDEF void
	colorin_init (compress_info_ptr cinfo)
	{
	/* Allocate a workspace for the result of get_input_row. */
	pixel_row = (*cinfo->emethods->alloc_small_sarray)
	(cinfo->image_width, (long) cinfo->input_components);
	}


	/*
	* Fetch some rows of pixels from get_input_row and convert to the
	* JPEG colorspace.
	* This version handles grayscale output with no conversion.
	* The source can be either plain grayscale or YCbCr (since Y == gray).
	*/

	METHODDEF void
	get_grayscale_rows (compress_info_ptr cinfo,
	int rows_to_read, JSAMPIMAGE image_data)
	{
	int row;

	for (row = 0; row < rows_to_read; row++) {
	/* Read one row from the source file */
	(*cinfo->methods->get_input_row) (cinfo, pixel_row);
	/* Convert colorspace (gamma mapping needed here) */
	jcopy_sample_rows(pixel_row, 0, image_data[0], row,
	1, cinfo->image_width);
	}
	}


	/*
	* Fetch some rows of pixels from get_input_row and convert to the
	* JPEG colorspace.
	* This version handles multi-component colorspaces without conversion.
	*/

	METHODDEF void
	get_noconvert_rows (compress_info_ptr cinfo,
	int rows_to_read, JSAMPIMAGE image_data)
	{
	int row, ci;

	for (row = 0; row < rows_to_read; row++) {
	/* Read one row from the source file */
	(*cinfo->methods->get_input_row) (cinfo, pixel_row);
	/* Convert colorspace (gamma mapping needed here) */
	for (ci = 0; ci < cinfo->input_components; ci++) {
	jcopy_sample_rows(pixel_row, ci, image_data[ci], row,
	1, cinfo->image_width);
	}
	}
	}


	/*
	* Finish up at the end of the file.
	*/

	METHODDEF void
	colorin_term (compress_info_ptr cinfo)
	{
	/* no work (we let free_all release the workspace) */
	}


	/*
	* The method selection routine for input colorspace conversion.
	*/

	GLOBAL void
	jselccolor (compress_info_ptr cinfo)
	{
	/* Make sure input_components agrees with in_color_space */
	switch (cinfo->in_color_space) {
	case CS_GRAYSCALE:
	if (cinfo->input_components != 1)
	ERREXIT(cinfo->emethods, "Bogus input colorspace");
	break;

	case CS_RGB:
	case CS_YCbCr:
	case CS_YIQ:
	if (cinfo->input_components != 3)
	ERREXIT(cinfo->emethods, "Bogus input colorspace");
	break;

	case CS_CMYK:
	if (cinfo->input_components != 4)
	ERREXIT(cinfo->emethods, "Bogus input colorspace");
	break;

	default:
	ERREXIT(cinfo->emethods, "Unsupported input colorspace");
	break;
	}

	/* Standard init/term methods (may override below) */
	cinfo->methods->colorin_init = colorin_init;
	cinfo->methods->colorin_term = colorin_term;

	/* Check num_components, set conversion method based on requested space */
	switch (cinfo->jpeg_color_space) {
	case CS_GRAYSCALE:
	if (cinfo->num_components != 1)
	ERREXIT(cinfo->emethods, "Bogus JPEG colorspace");
	if (cinfo->in_color_space == CS_GRAYSCALE)
	cinfo->methods->get_sample_rows = get_grayscale_rows;
	else if (cinfo->in_color_space == CS_RGB) {
	cinfo->methods->colorin_init = rgb_ycc_init;
	cinfo->methods->get_sample_rows = get_rgb_gray_rows;
	} else if (cinfo->in_color_space == CS_YCbCr)
	cinfo->methods->get_sample_rows = get_grayscale_rows;
	else
	ERREXIT(cinfo->emethods, "Unsupported color conversion request");
	break;

	case CS_YCbCr:
	if (cinfo->num_components != 3)
	ERREXIT(cinfo->emethods, "Bogus JPEG colorspace");
	if (cinfo->in_color_space == CS_RGB) {
	cinfo->methods->colorin_init = rgb_ycc_init;
	cinfo->methods->get_sample_rows = get_rgb_ycc_rows;
	} else if (cinfo->in_color_space == CS_YCbCr)
	cinfo->methods->get_sample_rows = get_noconvert_rows;
	else
	ERREXIT(cinfo->emethods, "Unsupported color conversion request");
	break;

	case CS_CMYK:
	if (cinfo->num_components != 4)
	ERREXIT(cinfo->emethods, "Bogus JPEG colorspace");
	if (cinfo->in_color_space == CS_CMYK)
	cinfo->methods->get_sample_rows = get_noconvert_rows;
	else
	ERREXIT(cinfo->emethods, "Unsupported color conversion request");
	break;

	default:
	ERREXIT(cinfo->emethods, "Unsupported JPEG colorspace");
	break;
	}
	}