src/jpeg/jdcolor.c

/*
 * 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 */
  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);
}


/*
 * 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 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_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;
}
Commit	Line	Data
	1	/*
	2	* jdcolor.c
	3	*
	4	* Copyright (C) 1991-1997, Thomas G. Lane.
	5	* This file is part of the Independent JPEG Group's software.
	6	* For conditions of distribution and use, see the accompanying README file.
	7	*
	8	* This file contains output colorspace conversion routines.
	9	*/
	10
	11	#define JPEG_INTERNALS
	12	#include "jinclude.h"
	13	#include "jpeglib.h"
	14
	15
	16	/* Private subobject */
	17
	18	typedef struct {
	19	struct jpeg_color_deconverter pub; /* public fields */
	20
	21	/* Private state for YCC->RGB conversion */
	22	int * Cr_r_tab; /* => table for Cr to R conversion */
	23	int * Cb_b_tab; /* => table for Cb to B conversion */
	24	INT32 * Cr_g_tab; /* => table for Cr to G conversion */
	25	INT32 * Cb_g_tab; /* => table for Cb to G conversion */
	26	} my_color_deconverter;
	27
	28	typedef my_color_deconverter * my_cconvert_ptr;
	29
	30
	31	/************** YCbCr -> RGB conversion: most common case ************/
	32
	33	/*
	34	* YCbCr is defined per CCIR 601-1, except that Cb and Cr are
	35	* normalized to the range 0..MAXJSAMPLE rather than -0.5 .. 0.5.
	36	* The conversion equations to be implemented are therefore
	37	* R = Y + 1.40200 * Cr
	38	* G = Y - 0.34414 * Cb - 0.71414 * Cr
	39	* B = Y + 1.77200 * Cb
	40	* where Cb and Cr represent the incoming values less CENTERJSAMPLE.
	41	* (These numbers are derived from TIFF 6.0 section 21, dated 3-June-92.)
	42	*
	43	* To avoid floating-point arithmetic, we represent the fractional constants
	44	* as integers scaled up by 2^16 (about 4 digits precision); we have to divide
	45	* the products by 2^16, with appropriate rounding, to get the correct answer.
	46	* Notice that Y, being an integral input, does not contribute any fraction
	47	* so it need not participate in the rounding.
	48	*
	49	* For even more speed, we avoid doing any multiplications in the inner loop
	50	* by precalculating the constants times Cb and Cr for all possible values.
	51	* For 8-bit JSAMPLEs this is very reasonable (only 256 entries per table);
	52	* for 12-bit samples it is still acceptable. It's not very reasonable for
	53	* 16-bit samples, but if you want lossless storage you shouldn't be changing
	54	* colorspace anyway.
	55	* The Cr=>R and Cb=>B values can be rounded to integers in advance; the
	56	* values for the G calculation are left scaled up, since we must add them
	57	* together before rounding.
	58	*/
	59
	60	#define SCALEBITS 16 /* speediest right-shift on some machines */
	61	#define ONE_HALF ((INT32) 1 << (SCALEBITS-1))
	62	#define FIX(x) ((INT32) ((x) * (1L<<SCALEBITS) + 0.5))
	63
	64
	65	/*
	66	* Initialize tables for YCC->RGB colorspace conversion.
	67	*/
	68
	69	LOCAL(void)
	70	build_ycc_rgb_table (j_decompress_ptr cinfo)
	71	{
	72	my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
	73	int i;
	74	INT32 x;
	75	SHIFT_TEMPS
	76
	77	cconvert->Cr_r_tab = (int *)
	78	(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
	79	(MAXJSAMPLE+1) * SIZEOF(int));
	80	cconvert->Cb_b_tab = (int *)
	81	(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
	82	(MAXJSAMPLE+1) * SIZEOF(int));
	83	cconvert->Cr_g_tab = (INT32 *)
	84	(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
	85	(MAXJSAMPLE+1) * SIZEOF(INT32));
	86	cconvert->Cb_g_tab = (INT32 *)
	87	(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
	88	(MAXJSAMPLE+1) * SIZEOF(INT32));
	89
	90	for (i = 0, x = -CENTERJSAMPLE; i <= MAXJSAMPLE; i++, x++) {
	91	/* i is the actual input pixel value, in the range 0..MAXJSAMPLE */
	92	/* The Cb or Cr value we are thinking of is x = i - CENTERJSAMPLE */
	93	/* Cr=>R value is nearest int to 1.40200 * x */
	94	cconvert->Cr_r_tab[i] = (int)
	95	RIGHT_SHIFT(FIX(1.40200) * x + ONE_HALF, SCALEBITS);
	96	/* Cb=>B value is nearest int to 1.77200 * x */
	97	cconvert->Cb_b_tab[i] = (int)
	98	RIGHT_SHIFT(FIX(1.77200) * x + ONE_HALF, SCALEBITS);
	99	/* Cr=>G value is scaled-up -0.71414 * x */
	100	cconvert->Cr_g_tab[i] = (- FIX(0.71414)) * x;
	101	/* Cb=>G value is scaled-up -0.34414 * x */
	102	/* We also add in ONE_HALF so that need not do it in inner loop */
	103	cconvert->Cb_g_tab[i] = (- FIX(0.34414)) * x + ONE_HALF;
	104	}
	105	}
	106
	107
	108	/*
	109	* Convert some rows of samples to the output colorspace.
	110	*
	111	* Note that we change from noninterleaved, one-plane-per-component format
	112	* to interleaved-pixel format. The output buffer is therefore three times
	113	* as wide as the input buffer.
	114	* A starting row offset is provided only for the input buffer. The caller
	115	* can easily adjust the passed output_buf value to accommodate any row
	116	* offset required on that side.
	117	*/
	118
	119	METHODDEF(void)
	120	ycc_rgb_convert (j_decompress_ptr cinfo,
	121	JSAMPIMAGE input_buf, JDIMENSION input_row,
	122	JSAMPARRAY output_buf, int num_rows)
	123	{
	124	my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
	125	register int y, cb, cr;
	126	register JSAMPROW outptr;
	127	register JSAMPROW inptr0, inptr1, inptr2;
	128	register JDIMENSION col;
	129	JDIMENSION num_cols = cinfo->output_width;
	130	/* copy these pointers into registers if possible */
	131	register JSAMPLE * range_limit = cinfo->sample_range_limit;
	132	register int * Crrtab = cconvert->Cr_r_tab;
	133	register int * Cbbtab = cconvert->Cb_b_tab;
	134	register INT32 * Crgtab = cconvert->Cr_g_tab;
	135	register INT32 * Cbgtab = cconvert->Cb_g_tab;
	136	SHIFT_TEMPS
	137
	138	while (--num_rows >= 0) {
	139	inptr0 = input_buf[0][input_row];
	140	inptr1 = input_buf[1][input_row];
	141	inptr2 = input_buf[2][input_row];
	142	input_row++;
	143	outptr = *output_buf++;
	144	for (col = 0; col < num_cols; col++) {
	145	y = GETJSAMPLE(inptr0[col]);
	146	cb = GETJSAMPLE(inptr1[col]);
	147	cr = GETJSAMPLE(inptr2[col]);
	148	/* Range-limiting is essential due to noise introduced by DCT losses. */
	149	outptr[RGB_RED] = range_limit[y + Crrtab[cr]];
	150	outptr[RGB_GREEN] = range_limit[y +
	151	((int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr],
	152	SCALEBITS))];
	153	outptr[RGB_BLUE] = range_limit[y + Cbbtab[cb]];
	154	outptr += RGB_PIXELSIZE;
	155	}
	156	}
	157	}
	158
	159
	160	/************** Cases other than YCbCr -> RGB ************/
	161
	162
	163	/*
	164	* Color conversion for no colorspace change: just copy the data,
	165	* converting from separate-planes to interleaved representation.
	166	*/
	167
	168	METHODDEF(void)
	169	null_convert (j_decompress_ptr cinfo,
	170	JSAMPIMAGE input_buf, JDIMENSION input_row,
	171	JSAMPARRAY output_buf, int num_rows)
	172	{
	173	register JSAMPROW inptr, outptr;
	174	register JDIMENSION count;
	175	register int num_components = cinfo->num_components;
	176	JDIMENSION num_cols = cinfo->output_width;
	177	int ci;
	178
	179	while (--num_rows >= 0) {
	180	for (ci = 0; ci < num_components; ci++) {
	181	inptr = input_buf[ci][input_row];
	182	outptr = output_buf[0] + ci;
	183	for (count = num_cols; count > 0; count--) {
	184	outptr = inptr++; /* needn't bother with GETJSAMPLE() here */
	185	outptr += num_components;
	186	}
	187	}
	188	input_row++;
	189	output_buf++;
	190	}
	191	}
	192
	193
	194	/*
	195	* Color conversion for grayscale: just copy the data.
	196	* This also works for YCbCr -> grayscale conversion, in which
	197	* we just copy the Y (luminance) component and ignore chrominance.
	198	*/
	199
	200	METHODDEF(void)
	201	grayscale_convert (j_decompress_ptr cinfo,
	202	JSAMPIMAGE input_buf, JDIMENSION input_row,
	203	JSAMPARRAY output_buf, int num_rows)
	204	{
	205	jcopy_sample_rows(input_buf[0], (int) input_row, output_buf, 0,
	206	num_rows, cinfo->output_width);
	207	}
	208
	209
	210	/*
	211	* Convert grayscale to RGB: just duplicate the graylevel three times.
	212	* This is provided to support applications that don't want to cope
	213	* with grayscale as a separate case.
	214	*/
	215
	216	METHODDEF(void)
	217	gray_rgb_convert (j_decompress_ptr cinfo,
	218	JSAMPIMAGE input_buf, JDIMENSION input_row,
	219	JSAMPARRAY output_buf, int num_rows)
	220	{
	221	register JSAMPROW inptr, outptr;
	222	register JDIMENSION col;
	223	JDIMENSION num_cols = cinfo->output_width;
	224
	225	while (--num_rows >= 0) {
	226	inptr = input_buf[0][input_row++];
	227	outptr = *output_buf++;
	228	for (col = 0; col < num_cols; col++) {
	229	/* We can dispense with GETJSAMPLE() here */
	230	outptr[RGB_RED] = outptr[RGB_GREEN] = outptr[RGB_BLUE] = inptr[col];
	231	outptr += RGB_PIXELSIZE;
	232	}
	233	}
	234	}
	235
	236
	237	/*
	238	* Adobe-style YCCK->CMYK conversion.
	239	* We convert YCbCr to R=1-C, G=1-M, and B=1-Y using the same
	240	* conversion as above, while passing K (black) unchanged.
	241	* We assume build_ycc_rgb_table has been called.
	242	*/
	243
	244	METHODDEF(void)
	245	ycck_cmyk_convert (j_decompress_ptr cinfo,
	246	JSAMPIMAGE input_buf, JDIMENSION input_row,
	247	JSAMPARRAY output_buf, int num_rows)
	248	{
	249	my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
	250	register int y, cb, cr;
	251	register JSAMPROW outptr;
	252	register JSAMPROW inptr0, inptr1, inptr2, inptr3;
	253	register JDIMENSION col;
	254	JDIMENSION num_cols = cinfo->output_width;
	255	/* copy these pointers into registers if possible */
	256	register JSAMPLE * range_limit = cinfo->sample_range_limit;
	257	register int * Crrtab = cconvert->Cr_r_tab;
	258	register int * Cbbtab = cconvert->Cb_b_tab;
	259	register INT32 * Crgtab = cconvert->Cr_g_tab;
	260	register INT32 * Cbgtab = cconvert->Cb_g_tab;
	261	SHIFT_TEMPS
	262
	263	while (--num_rows >= 0) {
	264	inptr0 = input_buf[0][input_row];
	265	inptr1 = input_buf[1][input_row];
	266	inptr2 = input_buf[2][input_row];
	267	inptr3 = input_buf[3][input_row];
	268	input_row++;
	269	outptr = *output_buf++;
	270	for (col = 0; col < num_cols; col++) {
	271	y = GETJSAMPLE(inptr0[col]);
	272	cb = GETJSAMPLE(inptr1[col]);
	273	cr = GETJSAMPLE(inptr2[col]);
	274	/* Range-limiting is essential due to noise introduced by DCT losses. */
	275	outptr[0] = range_limit[MAXJSAMPLE - (y + Crrtab[cr])]; /* red */
	276	outptr[1] = range_limit[MAXJSAMPLE - (y + /* green */
	277	((int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr],
	278	SCALEBITS)))];
	279	outptr[2] = range_limit[MAXJSAMPLE - (y + Cbbtab[cb])]; /* blue */
	280	/* K passes through unchanged */
	281	outptr[3] = inptr3[col]; /* don't need GETJSAMPLE here */
	282	outptr += 4;
	283	}
	284	}
	285	}
	286
	287
	288	/*
	289	* Empty method for start_pass.
	290	*/
	291
	292	METHODDEF(void)
	293	start_pass_dcolor (j_decompress_ptr cinfo)
	294	{
	295	/* no work needed */
	296	}
	297
	298
	299	/*
	300	* Module initialization routine for output colorspace conversion.
	301	*/
	302
	303	GLOBAL(void)
	304	jinit_color_deconverter (j_decompress_ptr cinfo)
	305	{
	306	my_cconvert_ptr cconvert;
	307	int ci;
	308
	309	cconvert = (my_cconvert_ptr)
	310	(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
	311	SIZEOF(my_color_deconverter));
	312	cinfo->cconvert = (struct jpeg_color_deconverter *) cconvert;
	313	cconvert->pub.start_pass = start_pass_dcolor;
	314
	315	/* Make sure num_components agrees with jpeg_color_space */
	316	switch (cinfo->jpeg_color_space) {
	317	case JCS_GRAYSCALE:
	318	if (cinfo->num_components != 1)
	319	ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
	320	break;
	321
	322	case JCS_RGB:
	323	case JCS_YCbCr:
	324	if (cinfo->num_components != 3)
	325	ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
	326	break;
	327
	328	case JCS_CMYK:
	329	case JCS_YCCK:
	330	if (cinfo->num_components != 4)
	331	ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
	332	break;
	333
	334	default: /* JCS_UNKNOWN can be anything */
	335	if (cinfo->num_components < 1)
	336	ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
	337	break;
	338	}
	339
	340	/* Set out_color_components and conversion method based on requested space.
	341	* Also clear the component_needed flags for any unused components,
	342	* so that earlier pipeline stages can avoid useless computation.
	343	*/
	344
	345	switch (cinfo->out_color_space) {
	346	case JCS_GRAYSCALE:
	347	cinfo->out_color_components = 1;
	348	if (cinfo->jpeg_color_space == JCS_GRAYSCALE \|\|
	349	cinfo->jpeg_color_space == JCS_YCbCr) {
	350	cconvert->pub.color_convert = grayscale_convert;
	351	/* For color->grayscale conversion, only the Y (0) component is needed */
	352	for (ci = 1; ci < cinfo->num_components; ci++)
	353	cinfo->comp_info[ci].component_needed = FALSE;
	354	} else
	355	ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
	356	break;
	357
	358	case JCS_RGB:
	359	cinfo->out_color_components = RGB_PIXELSIZE;
	360	if (cinfo->jpeg_color_space == JCS_YCbCr) {
	361	cconvert->pub.color_convert = ycc_rgb_convert;
	362	build_ycc_rgb_table(cinfo);
	363	} else if (cinfo->jpeg_color_space == JCS_GRAYSCALE) {
	364	cconvert->pub.color_convert = gray_rgb_convert;
	365	} else if (cinfo->jpeg_color_space == JCS_RGB && RGB_PIXELSIZE == 3) {
	366	cconvert->pub.color_convert = null_convert;
	367	} else
	368	ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
	369	break;
	370
	371	case JCS_CMYK:
	372	cinfo->out_color_components = 4;
	373	if (cinfo->jpeg_color_space == JCS_YCCK) {
	374	cconvert->pub.color_convert = ycck_cmyk_convert;
	375	build_ycc_rgb_table(cinfo);
	376	} else if (cinfo->jpeg_color_space == JCS_CMYK) {
	377	cconvert->pub.color_convert = null_convert;
	378	} else
	379	ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
	380	break;
	381
	382	default:
	383	/* Permit null conversion to same output space */
	384	if (cinfo->out_color_space == cinfo->jpeg_color_space) {
	385	cinfo->out_color_components = cinfo->num_components;
	386	cconvert->pub.color_convert = null_convert;
	387	} else /* unsupported non-null conversion */
	388	ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
	389	break;
	390	}
	391
	392	if (cinfo->quantize_colors)
	393	cinfo->output_components = 1; /* single colormapped output component */
	394	else
	395	cinfo->output_components = cinfo->out_color_components;
	396	}