www.pudn.com > imgport.rar > jccolor.c, change:2008-11-05,size:15362b


/* 
 * 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; 
  } 
}