src/jpeg/jccolor.c

/*
 * jccolor.c
 *
 * Copyright (C) 1991-1996, 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.
 */

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


/* Private subobject */

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

  /* Private state for RGB->YCC conversion */
  JPEG_INT32 * rgb_ycc_tab;		/* => table for RGB to YCbCr conversion */
} my_color_converter;

typedef my_color_converter * my_cconvert_ptr;


/**************** 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  + CENTERJSAMPLE
 *	Cr =  0.50000 * R - 0.41869 * G - 0.08131 * B  + CENTERJSAMPLE
 * (These numbers are derived from TIFF 6.0 section 21, dated 3-June-92.)
 * Note: older versions of the IJG code used a zero offset of MAXJSAMPLE/2,
 * rather than CENTERJSAMPLE, for Cb and Cr.  This gave equal positive and
 * negative swings for Cb/Cr, but meant that grayscale values (Cb=Cr=0)
 * were not represented exactly.  Now we sacrifice exact representation of
 * maximum red and maximum blue in order to get exact grayscales.
 *
 * 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 CENTERJSAMPLE offsets and the rounding fudge-factor of 0.5 are included
 * in the tables to save adding them separately in the inner loop.
 */

#define SCALEBITS	16	/* speediest right-shift on some machines */
#define CBCR_OFFSET	((JPEG_INT32) CENTERJSAMPLE << SCALEBITS)
#define ONE_HALF	((JPEG_INT32) 1 << (SCALEBITS-1))
#define FIX(x)		((JPEG_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).
 */

#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 RGB->YCC colorspace conversion.
 */

METHODDEF(void)
rgb_ycc_start (j_compress_ptr cinfo)
{
  my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
  JPEG_INT32 * rgb_ycc_tab;
  JPEG_INT32 i;

  /* Allocate and fill in the conversion tables. */
  cconvert->rgb_ycc_tab = rgb_ycc_tab = (JPEG_INT32 *)
    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
				(TABLE_SIZE * SIZEOF(JPEG_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;
    /* We use a rounding fudge-factor of 0.5-epsilon for Cb and Cr.
     * This ensures that the maximum output will round to MAXJSAMPLE
     * not MAXJSAMPLE+1, and thus that we don't have to range-limit.
     */
    rgb_ycc_tab[i+B_CB_OFF] = FIX(0.50000) * i    + CBCR_OFFSET + ONE_HALF-1;
/*  B=>Cb and R=>Cr tables are the same
    rgb_ycc_tab[i+R_CR_OFF] = FIX(0.50000) * i    + CBCR_OFFSET + ONE_HALF-1;
*/
    rgb_ycc_tab[i+G_CR_OFF] = (-FIX(0.41869)) * i;
    rgb_ycc_tab[i+B_CR_OFF] = (-FIX(0.08131)) * i;
  }
}


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

METHODDEF(void)
rgb_ycc_convert (j_compress_ptr cinfo,
		 JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
		 JDIMENSION output_row, int num_rows)
{
  my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
  register int r, g, b;
  register JPEG_INT32 * ctab = cconvert->rgb_ycc_tab;
  register JSAMPROW inptr;
  register JSAMPROW outptr0, outptr1, outptr2;
  register JDIMENSION col;
  JDIMENSION num_cols = cinfo->image_width;

  while (--num_rows >= 0) {
    inptr = *input_buf++;
    outptr0 = output_buf[0][output_row];
    outptr1 = output_buf[1][output_row];
    outptr2 = output_buf[2][output_row];
    output_row++;
    for (col = 0; col < num_cols; col++) {
      r = GETJSAMPLE(inptr[RGB_RED]);
      g = GETJSAMPLE(inptr[RGB_GREEN]);
      b = GETJSAMPLE(inptr[RGB_BLUE]);
      inptr += RGB_PIXELSIZE;
      /* 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 **************/


/*
 * Convert some rows of samples 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_start has been called (we only use the Y tables).
 */

METHODDEF(void)
rgb_gray_convert (j_compress_ptr cinfo,
		  JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
		  JDIMENSION output_row, int num_rows)
{
  my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
  register int r, g, b;
  register JPEG_INT32 * ctab = cconvert->rgb_ycc_tab;
  register JSAMPROW inptr;
  register JSAMPROW outptr;
  register JDIMENSION col;
  JDIMENSION num_cols = cinfo->image_width;

  while (--num_rows >= 0) {
    inptr = *input_buf++;
    outptr = output_buf[0][output_row];
    output_row++;
    for (col = 0; col < num_cols; col++) {
      r = GETJSAMPLE(inptr[RGB_RED]);
      g = GETJSAMPLE(inptr[RGB_GREEN]);
      b = GETJSAMPLE(inptr[RGB_BLUE]);
      inptr += RGB_PIXELSIZE;
      /* Y */
      outptr[col] = (JSAMPLE)
		((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF])
		 >> SCALEBITS);
    }
  }
}


/*
 * Convert some rows of samples to the JPEG colorspace.
 * This version handles Adobe-style CMYK->YCCK conversion,
 * where we convert R=1-C, G=1-M, and B=1-Y to YCbCr using the same
 * conversion as above, while passing K (black) unchanged.
 * We assume rgb_ycc_start has been called.
 */

METHODDEF(void)
cmyk_ycck_convert (j_compress_ptr cinfo,
		   JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
		   JDIMENSION output_row, int num_rows)
{
  my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
  register int r, g, b;
  register JPEG_INT32 * ctab = cconvert->rgb_ycc_tab;
  register JSAMPROW inptr;
  register JSAMPROW outptr0, outptr1, outptr2, outptr3;
  register JDIMENSION col;
  JDIMENSION num_cols = cinfo->image_width;

  while (--num_rows >= 0) {
    inptr = *input_buf++;
    outptr0 = output_buf[0][output_row];
    outptr1 = output_buf[1][output_row];
    outptr2 = output_buf[2][output_row];
    outptr3 = output_buf[3][output_row];
    output_row++;
    for (col = 0; col < num_cols; col++) {
      r = MAXJSAMPLE - GETJSAMPLE(inptr[0]);
      g = MAXJSAMPLE - GETJSAMPLE(inptr[1]);
      b = MAXJSAMPLE - GETJSAMPLE(inptr[2]);
      /* K passes through as-is */
      outptr3[col] = inptr[3];	/* don't need GETJSAMPLE here */
      inptr += 4;
      /* 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);
    }
  }
}


/*
 * Convert some rows of samples 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)
grayscale_convert (j_compress_ptr cinfo,
		   JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
		   JDIMENSION output_row, int num_rows)
{
  register JSAMPROW inptr;
  register JSAMPROW outptr;
  register JDIMENSION col;
  JDIMENSION num_cols = cinfo->image_width;
  int instride = cinfo->input_components;

  while (--num_rows >= 0) {
    inptr = *input_buf++;
    outptr = output_buf[0][output_row];
    output_row++;
    for (col = 0; col < num_cols; col++) {
      outptr[col] = inptr[0];	/* don't need GETJSAMPLE() here */
      inptr += instride;
    }
  }
}


/*
 * Convert some rows of samples to the JPEG colorspace.
 * This version handles multi-component colorspaces without conversion.
 * We assume input_components == num_components.
 */

METHODDEF(void)
null_convert (j_compress_ptr cinfo,
	      JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
	      JDIMENSION output_row, int num_rows)
{
  register JSAMPROW inptr;
  register JSAMPROW outptr;
  register JDIMENSION col;
  register int ci;
  int nc = cinfo->num_components;
  JDIMENSION num_cols = cinfo->image_width;

  while (--num_rows >= 0) {
    /* It seems fastest to make a separate pass for each component. */
    for (ci = 0; ci < nc; ci++) {
      inptr = *input_buf;
      outptr = output_buf[ci][output_row];
      for (col = 0; col < num_cols; col++) {
	outptr[col] = inptr[ci]; /* don't need GETJSAMPLE() here */
	inptr += nc;
      }
    }
    input_buf++;
    output_row++;
  }
}


/*
 * Empty method for start_pass.
 */

METHODDEF(void)
null_method (j_compress_ptr cinfo)
{
  /* no work needed */
}


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

GLOBAL(void)
jinit_color_converter (j_compress_ptr cinfo)
{
  my_cconvert_ptr cconvert;

  cconvert = (my_cconvert_ptr)
    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
				SIZEOF(my_color_converter));
  cinfo->cconvert = (struct jpeg_color_converter *) cconvert;
  /* set start_pass to null method until we find out differently */
  cconvert->pub.start_pass = null_method;

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

  case JCS_RGB:
#if RGB_PIXELSIZE != 3
    if (cinfo->input_components != RGB_PIXELSIZE)
      ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
    break;
#endif /* else share code with YCbCr */

  case JCS_YCbCr:
    if (cinfo->input_components != 3)
      ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
    break;

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

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

  /* Check num_components, set conversion method based on requested space */
  switch (cinfo->jpeg_color_space) {
  case JCS_GRAYSCALE:
    if (cinfo->num_components != 1)
      ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
    if (cinfo->in_color_space == JCS_GRAYSCALE)
      cconvert->pub.color_convert = grayscale_convert;
    else if (cinfo->in_color_space == JCS_RGB) {
      cconvert->pub.start_pass = rgb_ycc_start;
      cconvert->pub.color_convert = rgb_gray_convert;
    } else if (cinfo->in_color_space == JCS_YCbCr)
      cconvert->pub.color_convert = grayscale_convert;
    else
      ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
    break;

  case JCS_RGB:
    if (cinfo->num_components != 3)
      ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
    if (cinfo->in_color_space == JCS_RGB && RGB_PIXELSIZE == 3)
      cconvert->pub.color_convert = null_convert;
    else
      ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
    break;

  case JCS_YCbCr:
    if (cinfo->num_components != 3)
      ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
    if (cinfo->in_color_space == JCS_RGB) {
      cconvert->pub.start_pass = rgb_ycc_start;
      cconvert->pub.color_convert = rgb_ycc_convert;
    } else if (cinfo->in_color_space == JCS_YCbCr)
      cconvert->pub.color_convert = null_convert;
    else
      ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
    break;

  case JCS_CMYK:
    if (cinfo->num_components != 4)
      ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
    if (cinfo->in_color_space == JCS_CMYK)
      cconvert->pub.color_convert = null_convert;
    else
      ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
    break;

  case JCS_YCCK:
    if (cinfo->num_components != 4)
      ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
    if (cinfo->in_color_space == JCS_CMYK) {
      cconvert->pub.start_pass = rgb_ycc_start;
      cconvert->pub.color_convert = cmyk_ycck_convert;
    } else if (cinfo->in_color_space == JCS_YCCK)
      cconvert->pub.color_convert = null_convert;
    else
      ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
    break;

  default:			/* allow null conversion of JCS_UNKNOWN */
    if (cinfo->jpeg_color_space != cinfo->in_color_space ||
	cinfo->num_components != cinfo->input_components)
      ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
    cconvert->pub.color_convert = null_convert;
    break;
  }
}
Commit	Line	Data
	1	/*
	2	* jccolor.c
	3	*
	4	* Copyright (C) 1991-1996, 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 input 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_converter pub; /* public fields */
	20
	21	/* Private state for RGB->YCC conversion */
	22	JPEG_INT32 * rgb_ycc_tab; /* => table for RGB to YCbCr conversion */
	23	} my_color_converter;
	24
	25	typedef my_color_converter * my_cconvert_ptr;
	26
	27
	28	/************** RGB -> YCbCr conversion: most common case ************/
	29
	30	/*
	31	* YCbCr is defined per CCIR 601-1, except that Cb and Cr are
	32	* normalized to the range 0..MAXJSAMPLE rather than -0.5 .. 0.5.
	33	* The conversion equations to be implemented are therefore
	34	* Y = 0.29900 * R + 0.58700 * G + 0.11400 * B
	35	* Cb = -0.16874 * R - 0.33126 * G + 0.50000 * B + CENTERJSAMPLE
	36	* Cr = 0.50000 * R - 0.41869 * G - 0.08131 * B + CENTERJSAMPLE
	37	* (These numbers are derived from TIFF 6.0 section 21, dated 3-June-92.)
	38	* Note: older versions of the IJG code used a zero offset of MAXJSAMPLE/2,
	39	* rather than CENTERJSAMPLE, for Cb and Cr. This gave equal positive and
	40	* negative swings for Cb/Cr, but meant that grayscale values (Cb=Cr=0)
	41	* were not represented exactly. Now we sacrifice exact representation of
	42	* maximum red and maximum blue in order to get exact grayscales.
	43	*
	44	* To avoid floating-point arithmetic, we represent the fractional constants
	45	* as integers scaled up by 2^16 (about 4 digits precision); we have to divide
	46	* the products by 2^16, with appropriate rounding, to get the correct answer.
	47	*
	48	* For even more speed, we avoid doing any multiplications in the inner loop
	49	* by precalculating the constants times R,G,B for all possible values.
	50	* For 8-bit JSAMPLEs this is very reasonable (only 256 entries per table);
	51	* for 12-bit samples it is still acceptable. It's not very reasonable for
	52	* 16-bit samples, but if you want lossless storage you shouldn't be changing
	53	* colorspace anyway.
	54	* The CENTERJSAMPLE offsets and the rounding fudge-factor of 0.5 are included
	55	* in the tables to save adding them separately in the inner loop.
	56	*/
	57
	58	#define SCALEBITS 16 /* speediest right-shift on some machines */
	59	#define CBCR_OFFSET ((JPEG_INT32) CENTERJSAMPLE << SCALEBITS)
	60	#define ONE_HALF ((JPEG_INT32) 1 << (SCALEBITS-1))
	61	#define FIX(x) ((JPEG_INT32) ((x) * (1L<<SCALEBITS) + 0.5))
	62
	63	/* We allocate one big table and divide it up into eight parts, instead of
	64	* doing eight alloc_small requests. This lets us use a single table base
	65	* address, which can be held in a register in the inner loops on many
	66	* machines (more than can hold all eight addresses, anyway).
	67	*/
	68
	69	#define R_Y_OFF 0 /* offset to R => Y section */
	70	#define G_Y_OFF (1(MAXJSAMPLE+1)) / offset to G => Y section */
	71	#define B_Y_OFF (2(MAXJSAMPLE+1)) / etc. */
	72	#define R_CB_OFF (3*(MAXJSAMPLE+1))
	73	#define G_CB_OFF (4*(MAXJSAMPLE+1))
	74	#define B_CB_OFF (5*(MAXJSAMPLE+1))
	75	#define R_CR_OFF B_CB_OFF /* B=>Cb, R=>Cr are the same */
	76	#define G_CR_OFF (6*(MAXJSAMPLE+1))
	77	#define B_CR_OFF (7*(MAXJSAMPLE+1))
	78	#define TABLE_SIZE (8*(MAXJSAMPLE+1))
	79
	80
	81	/*
	82	* Initialize for RGB->YCC colorspace conversion.
	83	*/
	84
	85	METHODDEF(void)
	86	rgb_ycc_start (j_compress_ptr cinfo)
	87	{
	88	my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
	89	JPEG_INT32 * rgb_ycc_tab;
	90	JPEG_INT32 i;
	91
	92	/* Allocate and fill in the conversion tables. */
	93	cconvert->rgb_ycc_tab = rgb_ycc_tab = (JPEG_INT32 *)
	94	(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
	95	(TABLE_SIZE * SIZEOF(JPEG_INT32)));
	96
	97	for (i = 0; i <= MAXJSAMPLE; i++) {
	98	rgb_ycc_tab[i+R_Y_OFF] = FIX(0.29900) * i;
	99	rgb_ycc_tab[i+G_Y_OFF] = FIX(0.58700) * i;
	100	rgb_ycc_tab[i+B_Y_OFF] = FIX(0.11400) * i + ONE_HALF;
	101	rgb_ycc_tab[i+R_CB_OFF] = (-FIX(0.16874)) * i;
	102	rgb_ycc_tab[i+G_CB_OFF] = (-FIX(0.33126)) * i;
	103	/* We use a rounding fudge-factor of 0.5-epsilon for Cb and Cr.
	104	* This ensures that the maximum output will round to MAXJSAMPLE
	105	* not MAXJSAMPLE+1, and thus that we don't have to range-limit.
	106	*/
	107	rgb_ycc_tab[i+B_CB_OFF] = FIX(0.50000) * i + CBCR_OFFSET + ONE_HALF-1;
	108	/* B=>Cb and R=>Cr tables are the same
	109	rgb_ycc_tab[i+R_CR_OFF] = FIX(0.50000) * i + CBCR_OFFSET + ONE_HALF-1;
	110	*/
	111	rgb_ycc_tab[i+G_CR_OFF] = (-FIX(0.41869)) * i;
	112	rgb_ycc_tab[i+B_CR_OFF] = (-FIX(0.08131)) * i;
	113	}
	114	}
	115
	116
	117	/*
	118	* Convert some rows of samples to the JPEG colorspace.
	119	*
	120	* Note that we change from the application's interleaved-pixel format
	121	* to our internal noninterleaved, one-plane-per-component format.
	122	* The input buffer is therefore three times as wide as the output buffer.
	123	*
	124	* A starting row offset is provided only for the output buffer. The caller
	125	* can easily adjust the passed input_buf value to accommodate any row
	126	* offset required on that side.
	127	*/
	128
	129	METHODDEF(void)
	130	rgb_ycc_convert (j_compress_ptr cinfo,
	131	JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
	132	JDIMENSION output_row, int num_rows)
	133	{
	134	my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
	135	register int r, g, b;
	136	register JPEG_INT32 * ctab = cconvert->rgb_ycc_tab;
	137	register JSAMPROW inptr;
	138	register JSAMPROW outptr0, outptr1, outptr2;
	139	register JDIMENSION col;
	140	JDIMENSION num_cols = cinfo->image_width;
	141
	142	while (--num_rows >= 0) {
	143	inptr = *input_buf++;
	144	outptr0 = output_buf[0][output_row];
	145	outptr1 = output_buf[1][output_row];
	146	outptr2 = output_buf[2][output_row];
	147	output_row++;
	148	for (col = 0; col < num_cols; col++) {
	149	r = GETJSAMPLE(inptr[RGB_RED]);
	150	g = GETJSAMPLE(inptr[RGB_GREEN]);
	151	b = GETJSAMPLE(inptr[RGB_BLUE]);
	152	inptr += RGB_PIXELSIZE;
	153	/* If the inputs are 0..MAXJSAMPLE, the outputs of these equations
	154	* must be too; we do not need an explicit range-limiting operation.
	155	* Hence the value being shifted is never negative, and we don't
	156	* need the general RIGHT_SHIFT macro.
	157	*/
	158	/* Y */
	159	outptr0[col] = (JSAMPLE)
	160	((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF])
	161	>> SCALEBITS);
	162	/* Cb */
	163	outptr1[col] = (JSAMPLE)
	164	((ctab[r+R_CB_OFF] + ctab[g+G_CB_OFF] + ctab[b+B_CB_OFF])
	165	>> SCALEBITS);
	166	/* Cr */
	167	outptr2[col] = (JSAMPLE)
	168	((ctab[r+R_CR_OFF] + ctab[g+G_CR_OFF] + ctab[b+B_CR_OFF])
	169	>> SCALEBITS);
	170	}
	171	}
	172	}
	173
	174
	175	/************** Cases other than RGB -> YCbCr ************/
	176
	177
	178	/*
	179	* Convert some rows of samples to the JPEG colorspace.
	180	* This version handles RGB->grayscale conversion, which is the same
	181	* as the RGB->Y portion of RGB->YCbCr.
	182	* We assume rgb_ycc_start has been called (we only use the Y tables).
	183	*/
	184
	185	METHODDEF(void)
	186	rgb_gray_convert (j_compress_ptr cinfo,
	187	JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
	188	JDIMENSION output_row, int num_rows)
	189	{
	190	my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
	191	register int r, g, b;
	192	register JPEG_INT32 * ctab = cconvert->rgb_ycc_tab;
	193	register JSAMPROW inptr;
	194	register JSAMPROW outptr;
	195	register JDIMENSION col;
	196	JDIMENSION num_cols = cinfo->image_width;
	197
	198	while (--num_rows >= 0) {
	199	inptr = *input_buf++;
	200	outptr = output_buf[0][output_row];
	201	output_row++;
	202	for (col = 0; col < num_cols; col++) {
	203	r = GETJSAMPLE(inptr[RGB_RED]);
	204	g = GETJSAMPLE(inptr[RGB_GREEN]);
	205	b = GETJSAMPLE(inptr[RGB_BLUE]);
	206	inptr += RGB_PIXELSIZE;
	207	/* Y */
	208	outptr[col] = (JSAMPLE)
	209	((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF])
	210	>> SCALEBITS);
	211	}
	212	}
	213	}
	214
	215
	216	/*
	217	* Convert some rows of samples to the JPEG colorspace.
	218	* This version handles Adobe-style CMYK->YCCK conversion,
	219	* where we convert R=1-C, G=1-M, and B=1-Y to YCbCr using the same
	220	* conversion as above, while passing K (black) unchanged.
	221	* We assume rgb_ycc_start has been called.
	222	*/
	223
	224	METHODDEF(void)
	225	cmyk_ycck_convert (j_compress_ptr cinfo,
	226	JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
	227	JDIMENSION output_row, int num_rows)
	228	{
	229	my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
	230	register int r, g, b;
	231	register JPEG_INT32 * ctab = cconvert->rgb_ycc_tab;
	232	register JSAMPROW inptr;
	233	register JSAMPROW outptr0, outptr1, outptr2, outptr3;
	234	register JDIMENSION col;
	235	JDIMENSION num_cols = cinfo->image_width;
	236
	237	while (--num_rows >= 0) {
	238	inptr = *input_buf++;
	239	outptr0 = output_buf[0][output_row];
	240	outptr1 = output_buf[1][output_row];
	241	outptr2 = output_buf[2][output_row];
	242	outptr3 = output_buf[3][output_row];
	243	output_row++;
	244	for (col = 0; col < num_cols; col++) {
	245	r = MAXJSAMPLE - GETJSAMPLE(inptr[0]);
	246	g = MAXJSAMPLE - GETJSAMPLE(inptr[1]);
	247	b = MAXJSAMPLE - GETJSAMPLE(inptr[2]);
	248	/* K passes through as-is */
	249	outptr3[col] = inptr[3]; /* don't need GETJSAMPLE here */
	250	inptr += 4;
	251	/* If the inputs are 0..MAXJSAMPLE, the outputs of these equations
	252	* must be too; we do not need an explicit range-limiting operation.
	253	* Hence the value being shifted is never negative, and we don't
	254	* need the general RIGHT_SHIFT macro.
	255	*/
	256	/* Y */
	257	outptr0[col] = (JSAMPLE)
	258	((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF])
	259	>> SCALEBITS);
	260	/* Cb */
	261	outptr1[col] = (JSAMPLE)
	262	((ctab[r+R_CB_OFF] + ctab[g+G_CB_OFF] + ctab[b+B_CB_OFF])
	263	>> SCALEBITS);
	264	/* Cr */
	265	outptr2[col] = (JSAMPLE)
	266	((ctab[r+R_CR_OFF] + ctab[g+G_CR_OFF] + ctab[b+B_CR_OFF])
	267	>> SCALEBITS);
	268	}
	269	}
	270	}
	271
	272
	273	/*
	274	* Convert some rows of samples to the JPEG colorspace.
	275	* This version handles grayscale output with no conversion.
	276	* The source can be either plain grayscale or YCbCr (since Y == gray).
	277	*/
	278
	279	METHODDEF(void)
	280	grayscale_convert (j_compress_ptr cinfo,
	281	JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
	282	JDIMENSION output_row, int num_rows)
	283	{
	284	register JSAMPROW inptr;
	285	register JSAMPROW outptr;
	286	register JDIMENSION col;
	287	JDIMENSION num_cols = cinfo->image_width;
	288	int instride = cinfo->input_components;
	289
	290	while (--num_rows >= 0) {
	291	inptr = *input_buf++;
	292	outptr = output_buf[0][output_row];
	293	output_row++;
	294	for (col = 0; col < num_cols; col++) {
	295	outptr[col] = inptr[0]; /* don't need GETJSAMPLE() here */
	296	inptr += instride;
	297	}
	298	}
	299	}
	300
	301
	302	/*
	303	* Convert some rows of samples to the JPEG colorspace.
	304	* This version handles multi-component colorspaces without conversion.
	305	* We assume input_components == num_components.
	306	*/
	307
	308	METHODDEF(void)
	309	null_convert (j_compress_ptr cinfo,
	310	JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
	311	JDIMENSION output_row, int num_rows)
	312	{
	313	register JSAMPROW inptr;
	314	register JSAMPROW outptr;
	315	register JDIMENSION col;
	316	register int ci;
	317	int nc = cinfo->num_components;
	318	JDIMENSION num_cols = cinfo->image_width;
	319
	320	while (--num_rows >= 0) {
	321	/* It seems fastest to make a separate pass for each component. */
	322	for (ci = 0; ci < nc; ci++) {
	323	inptr = *input_buf;
	324	outptr = output_buf[ci][output_row];
	325	for (col = 0; col < num_cols; col++) {
	326	outptr[col] = inptr[ci]; /* don't need GETJSAMPLE() here */
	327	inptr += nc;
	328	}
	329	}
	330	input_buf++;
	331	output_row++;
	332	}
	333	}
	334
	335
	336	/*
	337	* Empty method for start_pass.
	338	*/
	339
	340	METHODDEF(void)
	341	null_method (j_compress_ptr cinfo)
	342	{
	343	/* no work needed */
	344	}
	345
	346
	347	/*
	348	* Module initialization routine for input colorspace conversion.
	349	*/
	350
	351	GLOBAL(void)
	352	jinit_color_converter (j_compress_ptr cinfo)
	353	{
	354	my_cconvert_ptr cconvert;
	355
	356	cconvert = (my_cconvert_ptr)
	357	(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
	358	SIZEOF(my_color_converter));
	359	cinfo->cconvert = (struct jpeg_color_converter *) cconvert;
	360	/* set start_pass to null method until we find out differently */
	361	cconvert->pub.start_pass = null_method;
	362
	363	/* Make sure input_components agrees with in_color_space */
	364	switch (cinfo->in_color_space) {
	365	case JCS_GRAYSCALE:
	366	if (cinfo->input_components != 1)
	367	ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
	368	break;
	369
	370	case JCS_RGB:
	371	#if RGB_PIXELSIZE != 3
	372	if (cinfo->input_components != RGB_PIXELSIZE)
	373	ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
	374	break;
	375	#endif /* else share code with YCbCr */
	376
	377	case JCS_YCbCr:
	378	if (cinfo->input_components != 3)
	379	ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
	380	break;
	381
	382	case JCS_CMYK:
	383	case JCS_YCCK:
	384	if (cinfo->input_components != 4)
	385	ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
	386	break;
	387
	388	default: /* JCS_UNKNOWN can be anything */
	389	if (cinfo->input_components < 1)
	390	ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
	391	break;
	392	}
	393
	394	/* Check num_components, set conversion method based on requested space */
	395	switch (cinfo->jpeg_color_space) {
	396	case JCS_GRAYSCALE:
	397	if (cinfo->num_components != 1)
	398	ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
	399	if (cinfo->in_color_space == JCS_GRAYSCALE)
	400	cconvert->pub.color_convert = grayscale_convert;
	401	else if (cinfo->in_color_space == JCS_RGB) {
	402	cconvert->pub.start_pass = rgb_ycc_start;
	403	cconvert->pub.color_convert = rgb_gray_convert;
	404	} else if (cinfo->in_color_space == JCS_YCbCr)
	405	cconvert->pub.color_convert = grayscale_convert;
	406	else
	407	ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
	408	break;
	409
	410	case JCS_RGB:
	411	if (cinfo->num_components != 3)
	412	ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
	413	if (cinfo->in_color_space == JCS_RGB && RGB_PIXELSIZE == 3)
	414	cconvert->pub.color_convert = null_convert;
	415	else
	416	ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
	417	break;
	418
	419	case JCS_YCbCr:
	420	if (cinfo->num_components != 3)
	421	ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
	422	if (cinfo->in_color_space == JCS_RGB) {
	423	cconvert->pub.start_pass = rgb_ycc_start;
	424	cconvert->pub.color_convert = rgb_ycc_convert;
	425	} else if (cinfo->in_color_space == JCS_YCbCr)
	426	cconvert->pub.color_convert = null_convert;
	427	else
	428	ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
	429	break;
	430
	431	case JCS_CMYK:
	432	if (cinfo->num_components != 4)
	433	ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
	434	if (cinfo->in_color_space == JCS_CMYK)
	435	cconvert->pub.color_convert = null_convert;
	436	else
	437	ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
	438	break;
	439
	440	case JCS_YCCK:
	441	if (cinfo->num_components != 4)
	442	ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
	443	if (cinfo->in_color_space == JCS_CMYK) {
	444	cconvert->pub.start_pass = rgb_ycc_start;
	445	cconvert->pub.color_convert = cmyk_ycck_convert;
	446	} else if (cinfo->in_color_space == JCS_YCCK)
	447	cconvert->pub.color_convert = null_convert;
	448	else
	449	ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
	450	break;
	451
	452	default: /* allow null conversion of JCS_UNKNOWN */
	453	if (cinfo->jpeg_color_space != cinfo->in_color_space \|\|
	454	cinfo->num_components != cinfo->input_components)
	455	ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
	456	cconvert->pub.color_convert = null_convert;
	457	break;
	458	}
	459	}