www.pudn.com > imgport.rar > jdmerge.c, change:2008-11-05,size:14379b


/* 
 * jdmerge.c 
 * 
 * Copyright (C) 1994-1996, 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 code for merged upsampling/color conversion. 
 * 
 * This file combines functions from jdsample.c and jdcolor.c; 
 * read those files first to understand what's going on. 
 * 
 * When the chroma components are to be upsampled by simple replication 
 * (ie, box filtering), we can save some work in color conversion by 
 * calculating all the output pixels corresponding to a pair of chroma 
 * samples at one time.  In the conversion equations 
 *	R = Y           + K1 * Cr 
 *	G = Y + K2 * Cb + K3 * Cr 
 *	B = Y + K4 * Cb 
 * only the Y term varies among the group of pixels corresponding to a pair 
 * of chroma samples, so the rest of the terms can be calculated just once. 
 * At typical sampling ratios, this eliminates half or three-quarters of the 
 * multiplications needed for color conversion. 
 * 
 * This file currently provides implementations for the following cases: 
 *	YCbCr => RGB color conversion only. 
 *	Sampling ratios of 2h1v or 2h2v. 
 *	No scaling needed at upsample time. 
 *	Corner-aligned (non-CCIR601) sampling alignment. 
 * Other special cases could be added, but in most applications these are 
 * the only common cases.  (For uncommon cases we fall back on the more 
 * general code in jdsample.c and jdcolor.c.) 
 */ 
 
#define JPEG_INTERNALS 
#include "jinclude.h" 
#include "jpeglib.h" 
 
#ifdef UPSAMPLE_MERGING_SUPPORTED 
 
 
/* Private subobject */ 
 
typedef struct { 
  struct jpeg_upsampler pub;	/* public fields */ 
 
  /* Pointer to routine to do actual upsampling/conversion of one row group */ 
  JMETHOD(void, upmethod, (j_decompress_ptr cinfo, 
			   JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr, 
			   JSAMPARRAY output_buf)); 
 
  /* 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 */ 
 
  /* For 2:1 vertical sampling, we produce two output rows at a time. 
   * We need a "spare" row buffer to hold the second output row if the 
   * application provides just a one-row buffer; we also use the spare 
   * to discard the dummy last row if the image height is odd. 
   */ 
  JSAMPROW spare_row; 
  boolean spare_full;		/* T if spare buffer is occupied */ 
 
  JDIMENSION out_row_width;	/* samples per output row */ 
  JDIMENSION rows_to_go;	/* counts rows remaining in image */ 
} my_upsampler; 
 
typedef my_upsampler * my_upsample_ptr; 
 
#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. 
 * This is taken directly from jdcolor.c; see that file for more info. 
 */ 
 
LOCAL(void) 
build_ycc_rgb_table (j_decompress_ptr cinfo) 
{ 
  my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample; 
  int i; 
  JPEG_INT32 x; 
  SHIFT_TEMPS 
 
  upsample->Cr_r_tab = (int *) 
    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 
				(MAXJSAMPLE+1) * SIZEOF(int)); 
  upsample->Cb_b_tab = (int *) 
    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 
				(MAXJSAMPLE+1) * SIZEOF(int)); 
  upsample->Cr_g_tab = (JPEG_INT32 *) 
    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 
				(MAXJSAMPLE+1) * SIZEOF(JPEG_INT32)); 
  upsample->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 */ 
    upsample->Cr_r_tab[i] = (int) 
		    RIGHT_SHIFT(FIX(1.40200) * x + ONE_HALF, SCALEBITS); 
    /* Cb=>B value is nearest int to 1.77200 * x */ 
    upsample->Cb_b_tab[i] = (int) 
		    RIGHT_SHIFT(FIX(1.77200) * x + ONE_HALF, SCALEBITS); 
    /* Cr=>G value is scaled-up -0.71414 * x */ 
    upsample->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 */ 
    upsample->Cb_g_tab[i] = (- FIX(0.34414)) * x + ONE_HALF; 
  } 
} 
 
 
/* 
 * Initialize for an upsampling pass. 
 */ 
 
METHODDEF(void) 
start_pass_merged_upsample (j_decompress_ptr cinfo) 
{ 
  my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample; 
 
  /* Mark the spare buffer empty */ 
  upsample->spare_full = FALSE; 
  /* Initialize total-height counter for detecting bottom of image */ 
  upsample->rows_to_go = cinfo->output_height; 
} 
 
 
/* 
 * Control routine to do upsampling (and color conversion). 
 * 
 * The control routine just handles the row buffering considerations. 
 */ 
 
METHODDEF(void) 
merged_2v_upsample (j_decompress_ptr cinfo, 
		    JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr, 
		    JDIMENSION in_row_groups_avail, 
		    JSAMPARRAY output_buf, JDIMENSION *out_row_ctr, 
		    JDIMENSION out_rows_avail) 
/* 2:1 vertical sampling case: may need a spare row. */ 
{ 
  my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample; 
  JSAMPROW work_ptrs[2]; 
  JDIMENSION num_rows;		/* number of rows returned to caller */ 
 
  if (upsample->spare_full) { 
    /* If we have a spare row saved from a previous cycle, just return it. */ 
    jcopy_sample_rows(& upsample->spare_row, 0, output_buf + *out_row_ctr, 0, 
		      1, upsample->out_row_width); 
    num_rows = 1; 
    upsample->spare_full = FALSE; 
  } else { 
    /* Figure number of rows to return to caller. */ 
    num_rows = 2; 
    /* Not more than the distance to the end of the image. */ 
    if (num_rows > upsample->rows_to_go) 
      num_rows = upsample->rows_to_go; 
    /* And not more than what the client can accept: */ 
    out_rows_avail -= *out_row_ctr; 
    if (num_rows > out_rows_avail) 
      num_rows = out_rows_avail; 
    /* Create output pointer array for upsampler. */ 
    work_ptrs[0] = output_buf[*out_row_ctr]; 
    if (num_rows > 1) { 
      work_ptrs[1] = output_buf[*out_row_ctr + 1]; 
    } else { 
      work_ptrs[1] = upsample->spare_row; 
      upsample->spare_full = TRUE; 
    } 
    /* Now do the upsampling. */ 
    (*upsample->upmethod) (cinfo, input_buf, *in_row_group_ctr, work_ptrs); 
  } 
 
  /* Adjust counts */ 
  *out_row_ctr += num_rows; 
  upsample->rows_to_go -= num_rows; 
  /* When the buffer is emptied, declare this input row group consumed */ 
  if (! upsample->spare_full) 
    (*in_row_group_ctr)++; 
} 
 
 
METHODDEF(void) 
merged_1v_upsample (j_decompress_ptr cinfo, 
		    JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr, 
		    JDIMENSION in_row_groups_avail, 
		    JSAMPARRAY output_buf, JDIMENSION *out_row_ctr, 
		    JDIMENSION out_rows_avail) 
/* 1:1 vertical sampling case: much easier, never need a spare row. */ 
{ 
  my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample; 
 
  /* Just do the upsampling. */ 
  (*upsample->upmethod) (cinfo, input_buf, *in_row_group_ctr, 
			 output_buf + *out_row_ctr); 
  /* Adjust counts */ 
  (*out_row_ctr)++; 
  (*in_row_group_ctr)++; 
} 
 
 
/* 
 * These are the routines invoked by the control routines to do 
 * the actual upsampling/conversion.  One row group is processed per call. 
 * 
 * Note: since we may be writing directly into application-supplied buffers, 
 * we have to be honest about the output width; we can't assume the buffer 
 * has been rounded up to an even width. 
 */ 
 
 
/* 
 * Upsample and color convert for the case of 2:1 horizontal and 1:1 vertical. 
 */ 
 
METHODDEF(void) 
h2v1_merged_upsample (j_decompress_ptr cinfo, 
		      JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr, 
		      JSAMPARRAY output_buf) 
{ 
  my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample; 
  register int y, cred, cgreen, cblue; 
  int cb, cr; 
  register JSAMPROW outptr; 
  JSAMPROW inptr0, inptr1, inptr2; 
  JDIMENSION col; 
  /* copy these pointers into registers if possible */ 
  register JSAMPLE * range_limit = cinfo->sample_range_limit; 
  int * Crrtab = upsample->Cr_r_tab; 
  int * Cbbtab = upsample->Cb_b_tab; 
  JPEG_INT32 * Crgtab = upsample->Cr_g_tab; 
  JPEG_INT32 * Cbgtab = upsample->Cb_g_tab; 
  SHIFT_TEMPS 
 
  inptr0 = input_buf[0][in_row_group_ctr]; 
  inptr1 = input_buf[1][in_row_group_ctr]; 
  inptr2 = input_buf[2][in_row_group_ctr]; 
  outptr = output_buf[0]; 
  /* Loop for each pair of output pixels */ 
  for (col = cinfo->output_width >> 1; col > 0; col--) { 
    /* Do the chroma part of the calculation */ 
    cb = GETJSAMPLE(*inptr1++); 
    cr = GETJSAMPLE(*inptr2++); 
    cred = Crrtab[cr]; 
    cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS); 
    cblue = Cbbtab[cb]; 
    /* Fetch 2 Y values and emit 2 pixels */ 
    y  = GETJSAMPLE(*inptr0++); 
    outptr[RGB_RED] =   range_limit[y + cred]; 
    outptr[RGB_GREEN] = range_limit[y + cgreen]; 
    outptr[RGB_BLUE] =  range_limit[y + cblue]; 
    outptr += RGB_PIXELSIZE; 
    y  = GETJSAMPLE(*inptr0++); 
    outptr[RGB_RED] =   range_limit[y + cred]; 
    outptr[RGB_GREEN] = range_limit[y + cgreen]; 
    outptr[RGB_BLUE] =  range_limit[y + cblue]; 
    outptr += RGB_PIXELSIZE; 
  } 
  /* If image width is odd, do the last output column separately */ 
  if (cinfo->output_width & 1) { 
    cb = GETJSAMPLE(*inptr1); 
    cr = GETJSAMPLE(*inptr2); 
    cred = Crrtab[cr]; 
    cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS); 
    cblue = Cbbtab[cb]; 
    y  = GETJSAMPLE(*inptr0); 
    outptr[RGB_RED] =   range_limit[y + cred]; 
    outptr[RGB_GREEN] = range_limit[y + cgreen]; 
    outptr[RGB_BLUE] =  range_limit[y + cblue]; 
  } 
} 
 
/* 
 * Upsample and color convert for the case of 2:1 horizontal and 2:1 vertical. 
 */ 
 
METHODDEF(void) 
h2v2_merged_upsample (j_decompress_ptr cinfo, 
		      JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr, 
		      JSAMPARRAY output_buf) 
{ 
  my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample; 
  register int y, cred, cgreen, cblue; 
  int cb, cr; 
  register JSAMPROW outptr0, outptr1; 
  JSAMPROW inptr00, inptr01, inptr1, inptr2; 
  JDIMENSION col; 
  /* copy these pointers into registers if possible */ 
  register JSAMPLE * range_limit = cinfo->sample_range_limit; 
  int * Crrtab = upsample->Cr_r_tab; 
  int * Cbbtab = upsample->Cb_b_tab; 
  JPEG_INT32 * Crgtab = upsample->Cr_g_tab; 
  JPEG_INT32 * Cbgtab = upsample->Cb_g_tab; 
  SHIFT_TEMPS 
 
  inptr00 = input_buf[0][in_row_group_ctr*2]; 
  inptr01 = input_buf[0][in_row_group_ctr*2 + 1]; 
  inptr1 = input_buf[1][in_row_group_ctr]; 
  inptr2 = input_buf[2][in_row_group_ctr]; 
  outptr0 = output_buf[0]; 
  outptr1 = output_buf[1]; 
  /* Loop for each group of output pixels */ 
  for (col = cinfo->output_width >> 1; col > 0; col--) { 
    /* Do the chroma part of the calculation */ 
    cb = GETJSAMPLE(*inptr1++); 
    cr = GETJSAMPLE(*inptr2++); 
    cred = Crrtab[cr]; 
    cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS); 
    cblue = Cbbtab[cb]; 
    /* Fetch 4 Y values and emit 4 pixels */ 
    y  = GETJSAMPLE(*inptr00++); 
    outptr0[RGB_RED] =   range_limit[y + cred]; 
    outptr0[RGB_GREEN] = range_limit[y + cgreen]; 
    outptr0[RGB_BLUE] =  range_limit[y + cblue]; 
    outptr0 += RGB_PIXELSIZE; 
    y  = GETJSAMPLE(*inptr00++); 
    outptr0[RGB_RED] =   range_limit[y + cred]; 
    outptr0[RGB_GREEN] = range_limit[y + cgreen]; 
    outptr0[RGB_BLUE] =  range_limit[y + cblue]; 
    outptr0 += RGB_PIXELSIZE; 
    y  = GETJSAMPLE(*inptr01++); 
    outptr1[RGB_RED] =   range_limit[y + cred]; 
    outptr1[RGB_GREEN] = range_limit[y + cgreen]; 
    outptr1[RGB_BLUE] =  range_limit[y + cblue]; 
    outptr1 += RGB_PIXELSIZE; 
    y  = GETJSAMPLE(*inptr01++); 
    outptr1[RGB_RED] =   range_limit[y + cred]; 
    outptr1[RGB_GREEN] = range_limit[y + cgreen]; 
    outptr1[RGB_BLUE] =  range_limit[y + cblue]; 
    outptr1 += RGB_PIXELSIZE; 
  } 
  /* If image width is odd, do the last output column separately */ 
  if (cinfo->output_width & 1) { 
    cb = GETJSAMPLE(*inptr1); 
    cr = GETJSAMPLE(*inptr2); 
    cred = Crrtab[cr]; 
    cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS); 
    cblue = Cbbtab[cb]; 
    y  = GETJSAMPLE(*inptr00); 
    outptr0[RGB_RED] =   range_limit[y + cred]; 
    outptr0[RGB_GREEN] = range_limit[y + cgreen]; 
    outptr0[RGB_BLUE] =  range_limit[y + cblue]; 
    y  = GETJSAMPLE(*inptr01); 
    outptr1[RGB_RED] =   range_limit[y + cred]; 
    outptr1[RGB_GREEN] = range_limit[y + cgreen]; 
    outptr1[RGB_BLUE] =  range_limit[y + cblue]; 
  } 
} 
 
 
/* 
 * Module initialization routine for merged upsampling/color conversion. 
 * 
 * NB: this is called under the conditions determined by use_merged_upsample() 
 * in jdmaster.c.  That routine MUST correspond to the actual capabilities 
 * of this module; no safety checks are made here. 
 */ 
 
GLOBAL(void) 
jinit_merged_upsampler (j_decompress_ptr cinfo) 
{ 
  my_upsample_ptr upsample; 
 
  upsample = (my_upsample_ptr) 
    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 
				SIZEOF(my_upsampler)); 
  cinfo->upsample = (struct jpeg_upsampler *) upsample; 
  upsample->pub.start_pass = start_pass_merged_upsample; 
  upsample->pub.need_context_rows = FALSE; 
 
  upsample->out_row_width = cinfo->output_width * cinfo->out_color_components; 
 
  if (cinfo->max_v_samp_factor == 2) { 
    upsample->pub.upsample = merged_2v_upsample; 
    upsample->upmethod = h2v2_merged_upsample; 
    /* Allocate a spare row buffer */ 
    upsample->spare_row = (JSAMPROW) 
      (*cinfo->mem->alloc_large) ((j_common_ptr) cinfo, JPOOL_IMAGE, 
		(size_t) (upsample->out_row_width * SIZEOF(JSAMPLE))); 
  } else { 
    upsample->pub.upsample = merged_1v_upsample; 
    upsample->upmethod = h2v1_merged_upsample; 
    /* No spare row needed */ 
    upsample->spare_row = NULL; 
  } 
 
  build_ycc_rgb_table(cinfo); 
} 
 
#endif /* UPSAMPLE_MERGING_SUPPORTED */