jcsample.c

EVM板JPEG实现,Texas Instruments TMS320C54x EVM JPEG

	  (input_cols % cinfo->max_h_samp_factor) != 0 ||
	  input_cols*compptr->h_samp_factor != output_cols*cinfo->max_h_samp_factor)
	ERREXIT(cinfo->emethods);
	(cinfo->emethods, "Bogus downsample parameters");
***************************************************************************/

#endif

  /* We don't bother to form the individual "smoothed" input pixel values;
   * we can directly compute the output which is the average of the four
   * smoothed values.  Each of the four member pixels contributes a fraction
   * (1-8*SF) to its own smoothed image and a fraction SF to each of the three
   * other smoothed pixels, therefore a total fraction (1-5*SF)/4 to the final
   * output.  The four corner-adjacent neighbor pixels contribute a fraction
   * SF to just one smoothed pixel, or SF/4 to the final output; while the
   * eight edge-adjacent neighbors contribute SF to each of two smoothed
   * pixels, or SF/2 overall.  In order to use integer arithmetic, these
   * factors are scaled by 2^16 = 65536.
   * Also recall that SF = smoothing_factor / 1024.
   */

  memberscale = 16384 - cinfo->smoothing_factor * 80; /* scaled (1-5*SF)/4 */
  neighscale = cinfo->smoothing_factor * 16; /* scaled SF/4 */

  inrow = 0;
  for (outrow = 0; outrow < output_rows; outrow++) {
	outptr = output_data[outrow];
	inptr0 = input_data[inrow];
	inptr1 = input_data[inrow+1];
	if (inrow == 0)
	  above_ptr = above[input_rows-1];
	else
	  above_ptr = input_data[inrow-1];
	if (inrow >= input_rows-2)
	  below_ptr = below[0];
	else
	  below_ptr = input_data[inrow+2];

	/* Special case for first column: pretend column -1 is same as column 0 */
	membersum = GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +
		GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]);
	neighsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[1]) +
		   GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[1]) +
		   GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[2]) +
		   GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[2]);
	neighsum += neighsum;
	neighsum += GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[2]) +
		GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[2]);
	membersum = membersum * memberscale + neighsum * neighscale;
	*outptr++ = (JSAMPLE) ((membersum + 32768L) >> 16);
	inptr0 += 2; inptr1 += 2; above_ptr += 2; below_ptr += 2;

	for (colctr = output_cols - 2; colctr > 0; colctr--) {
	  /* sum of pixels directly mapped to this output element */
	  membersum = GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +
		  GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]);
	  /* sum of edge-neighbor pixels */
	  neighsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[1]) +
		 GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[1]) +
		 GETJSAMPLE(inptr0[-1]) + GETJSAMPLE(inptr0[2]) +
		 GETJSAMPLE(inptr1[-1]) + GETJSAMPLE(inptr1[2]);
	  /* The edge-neighbors count twice as much as corner-neighbors */
	  neighsum += neighsum;
	  /* Add in the corner-neighbors */
	  neighsum += GETJSAMPLE(above_ptr[-1]) + GETJSAMPLE(above_ptr[2]) +
		  GETJSAMPLE(below_ptr[-1]) + GETJSAMPLE(below_ptr[2]);
	  /* form final output scaled up by 2^16 */
	  membersum = membersum * memberscale + neighsum * neighscale;
	  /* round, descale and output it */
	  *outptr++ = (JSAMPLE) ((membersum + 32768L) >> 16);
	  inptr0 += 2; inptr1 += 2; above_ptr += 2; below_ptr += 2;
	}

	/* Special case for last column */
	membersum = GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +
		GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1]);
	neighsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(above_ptr[1]) +
		   GETJSAMPLE(*below_ptr) + GETJSAMPLE(below_ptr[1]) +
		   GETJSAMPLE(inptr0[-1]) + GETJSAMPLE(inptr0[1]) +
		   GETJSAMPLE(inptr1[-1]) + GETJSAMPLE(inptr1[1]);
	neighsum += neighsum;
	neighsum += GETJSAMPLE(above_ptr[-1]) + GETJSAMPLE(above_ptr[1]) +
		GETJSAMPLE(below_ptr[-1]) + GETJSAMPLE(below_ptr[1]);
	membersum = membersum * memberscale + neighsum * neighscale;
	*outptr = (JSAMPLE) ((membersum + 32768L) >> 16);

	inrow += 2;
  }
}


/*
 * Downsample pixel values of a single component.
 * This version handles the special case of a full-size component,
 * with smoothing.
 */

METHODDEF void
fullsize_smooth_downsample (compress_info_ptr cinfo, int which_component,
				long input_cols, int input_rows,
				long output_cols, int output_rows,
				JSAMPARRAY above, JSAMPARRAY input_data, JSAMPARRAY below,
				JSAMPARRAY output_data)
{
  int outrow;
  long colctr;
  register JSAMPROW inptr, above_ptr, below_ptr, outptr;
  INT32 membersum, neighsum, memberscale, neighscale;
  int colsum, lastcolsum, nextcolsum;

#ifdef DEBUG            /* for debugging pipeline controller */
  if (input_cols != output_cols || input_rows != output_rows)
	ERREXIT(cinfo->emethods);
	/*(cinfo->emethods, "Pipeline controller messed up");*/
#endif

  /* Each of the eight neighbor pixels contributes a fraction SF to the
   * smoothed pixel, while the main pixel contributes (1-8*SF).  In order
   * to use integer arithmetic, these factors are multiplied by 2^16 = 65536.
   * Also recall that SF = smoothing_factor / 1024.
   */

  memberscale = 65536L - cinfo->smoothing_factor * 512L; /* scaled 1-8*SF */
  neighscale = cinfo->smoothing_factor * 64; /* scaled SF */

  for (outrow = 0; outrow < output_rows; outrow++) {
	outptr = output_data[outrow];
	inptr = input_data[outrow];
	if (outrow == 0)
	  above_ptr = above[input_rows-1];
	else
	  above_ptr = input_data[outrow-1];
	if (outrow >= input_rows-1)
	  below_ptr = below[0];
	else
	  below_ptr = input_data[outrow+1];

	/* Special case for first column */
	colsum = GETJSAMPLE(*above_ptr++) + GETJSAMPLE(*below_ptr++) +
		 GETJSAMPLE(*inptr);
	membersum = GETJSAMPLE(*inptr++);
	nextcolsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(*below_ptr) +
		 GETJSAMPLE(*inptr);
	neighsum = colsum + (colsum - membersum) + nextcolsum;
	membersum = membersum * memberscale + neighsum * neighscale;
	*outptr++ = (JSAMPLE) ((membersum + 32768L) >> 16);
	lastcolsum = colsum; colsum = nextcolsum;

	for (colctr = output_cols - 2; colctr > 0; colctr--) {
	  membersum = GETJSAMPLE(*inptr++);
	  above_ptr++; below_ptr++;
	  nextcolsum = GETJSAMPLE(*above_ptr) + GETJSAMPLE(*below_ptr) +
		   GETJSAMPLE(*inptr);
	  neighsum = lastcolsum + (colsum - membersum) + nextcolsum;
	  membersum = membersum * memberscale + neighsum * neighscale;
	  *outptr++ = (JSAMPLE) ((membersum + 32768L) >> 16);
	  lastcolsum = colsum; colsum = nextcolsum;
	}

	/* Special case for last column */
	membersum = GETJSAMPLE(*inptr);
	neighsum = lastcolsum + (colsum - membersum) + colsum;
	membersum = membersum * memberscale + neighsum * neighscale;
	*outptr = (JSAMPLE) ((membersum + 32768L) >> 16);

  }
}

#endif /* INPUT_SMOOTHING_SUPPORTED */


/*
 * Clean up after a scan.
 */

METHODDEF void
downsample_term (compress_info_ptr cinfo)
{
  /* no work for now */
}



/*
 * The method selection routine for downsampling.
 * Note that we must select a routine for each component.
 */

GLOBAL void
jseldownsample (compress_info_ptr cinfo)
{
  short ci;
  jpeg_component_info * compptr;
  boolean smoothok = TRUE;

/***********************DID NOT SUPPORT THIS ERROR**************************  
if (cinfo->CCIR601_sampling)
	ERREXIT(cinfo->emethods);
	(cinfo->emethods, "CCIR601 downsampling not implemented yet");
***************************************************************************/

  for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
	compptr = cinfo->cur_comp_info[ci];
	if (compptr->h_samp_factor == cinfo->max_h_samp_factor &&
	compptr->v_samp_factor == cinfo->max_v_samp_factor) {
#ifdef INPUT_SMOOTHING_SUPPORTED
	  if (cinfo->smoothing_factor)
	cinfo->methods->downsample[ci] = fullsize_smooth_downsample;
	  else
#endif
	cinfo->methods->downsample[ci] = fullsize_downsample;
	} else if (compptr->h_samp_factor * 2 == cinfo->max_h_samp_factor &&
		 compptr->v_samp_factor == cinfo->max_v_samp_factor) {
	  smoothok = FALSE;
	  cinfo->methods->downsample[ci] = h2v1_downsample;
	} else if (compptr->h_samp_factor * 2 == cinfo->max_h_samp_factor &&
		 compptr->v_samp_factor * 2 == cinfo->max_v_samp_factor) {
#ifdef INPUT_SMOOTHING_SUPPORTED
	  if (cinfo->smoothing_factor)
	cinfo->methods->downsample[ci] = h2v2_smooth_downsample;
	  else
#endif
	cinfo->methods->downsample[ci] = h2v2_downsample;
	} else if ((cinfo->max_h_samp_factor % compptr->h_samp_factor) == 0 &&
		 (cinfo->max_v_samp_factor % compptr->v_samp_factor) == 0) {
	  smoothok = FALSE;
	  cinfo->methods->downsample[ci] = int_downsample;
	} 

/***************************DID NOT SUPPORT THIS ERROR**********************    
	else
	ERREXIT(cinfo->emethods);
	  (cinfo->emethods, "Fractional downsampling not implemented yet");
***************************************************************************/

  }

#ifdef INPUT_SMOOTHING_SUPPORTED

/******************DID NOT SUPPORT THIS TRACE MESSAGE***********************  
  if (cinfo->smoothing_factor && !smoothok)
	TRACEMS(cinfo->emethods,0);
	(cinfo->emethods, 0,
		"Smoothing not supported with nonstandard sampling ratios");
***************************************************************************/

#endif

  cinfo->methods->downsample_init = downsample_init;
  cinfo->methods->downsample_term = downsample_term;
}