www.pudn.com > imgport.rar > jdcolor.c, change:2008-11-05,size:13820b


/* 
 * 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" 
 
#if defined(__VISAGECPP__) 
/* Visual Age fixups for multiple declarations */ 
#  define null_convert   null_convert2 /* already in jcmaint.c */ 
#  define grayscale_convert   grayscale_convert2 /* already in jcmaint.c */ 
#endif 
 
/* 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 */ 
  JPEG_INT32 * Cr_g_tab;		/* => table for Cr to G conversion */ 
  JPEG_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	((JPEG_INT32) 1 << (SCALEBITS-1)) 
#define FIX(x)		((JPEG_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; 
  JPEG_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 = (JPEG_INT32 *) 
    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 
				(MAXJSAMPLE+1) * SIZEOF(JPEG_INT32)); 
  cconvert->Cb_g_tab = (JPEG_INT32 *) 
    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 
				(MAXJSAMPLE+1) * SIZEOF(JPEG_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 JPEG_INT32 * Crgtab = cconvert->Cr_g_tab; 
  register JPEG_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 JPEG_INT32 * Crgtab = cconvert->Cr_g_tab; 
  register JPEG_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; 
} 
 
#if defined(__VISAGECPP__) 
#  ifdef null_convert2 
#   undef null_convert2 
#  endif 
#  ifdef grayscale_convert2 
#   undef grayscale_convert2 
#  endif 
#endif