jcsample.c

EVM板JPEG实现,Texas Instruments TMS320C54x EVM JPEG

/*
 * jcsample.c
 *
 * Copyright (C) 1991, 1992, 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 downsampling routines.
 * These routines are invoked via the downsample and
 * downsample_init/term methods.
 *
 * An excellent reference for image resampling is
 *   Digital Image Warping, George Wolberg, 1990.
 *   Pub. by IEEE Computer Society Press, Los Alamitos, CA. ISBN 0-8186-8944-7.
 *
 * The downsampling algorithm used here is a simple average of the source
 * pixels covered by the output pixel.  The hi-falutin sampling literature
 * refers to this as a "box filter".  In general the characteristics of a box
 * filter are not very good, but for the specific cases we normally use (1:1
 * and 2:1 ratios) the box is equivalent to a "triangle filter" which is not
 * nearly so bad.  If you intend to use other sampling ratios, you'd be well
 * advised to improve this code.
 *
 * A simple input-smoothing capability is provided.  This is mainly intended
 * for cleaning up color-dithered GIF input files (if you find it inadequate,
 * we suggest using an external filtering program such as pnmconvol).  When
 * enabled, each input pixel P is replaced by a weighted sum of itself and its
 * eight neighbors.  P's weight is 1-8*SF and each neighbor's weight is SF,
 * where SF = (smoothing_factor / 1024).
 * Currently, smoothing is only supported for 2h2v sampling factors.
 */

/* This file was changed to eliminate the error messages. Christopher Chang,
   Summer 1993.
*/

#include "jinclude.h"


/*
 * Initialize for downsampling a scan.
 */

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


/*
 * Downsample pixel values of a single component.
 * This version handles arbitrary integral sampling ratios, without smoothing.
 * Note that this version is not actually used for customary sampling ratios.
 */

METHODDEF void
int_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)
{
  jpeg_component_info * compptr = cinfo->cur_comp_info[which_component];
  int inrow, outrow, h_expand, v_expand, numpix, numpix2, h, v;
  long outcol, outcol_h;    /* outcol_h == outcol*h_expand */
  JSAMPROW inptr, outptr;
  INT32 outvalue;

#ifdef DEBUG            /* for debugging pipeline controller */
  
/*************************DID NOT SUPPORT THIS ERROR*************************  
  if (output_rows != compptr->v_samp_factor ||
	  input_rows != cinfo->max_v_samp_factor ||
	  (output_cols % compptr->h_samp_factor) != 0 ||
	  (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

  h_expand = cinfo->max_h_samp_factor / compptr->h_samp_factor;
  v_expand = cinfo->max_v_samp_factor / compptr->v_samp_factor;
  numpix = h_expand * v_expand;
  numpix2 = numpix/2;

  inrow = 0;
  for (outrow = 0; outrow < output_rows; outrow++) {
	outptr = output_data[outrow];
	for (outcol = 0, outcol_h = 0; outcol < output_cols;
	 outcol++, outcol_h += h_expand) {
	  outvalue = 0;
	  for (v = 0; v < v_expand; v++) {
	inptr = input_data[inrow+v] + outcol_h;
	for (h = 0; h < h_expand; h++) {
	  outvalue += (INT32) GETJSAMPLE(*inptr++);
	}
	  }
	  *outptr++ = (JSAMPLE) ((outvalue + numpix2) / numpix);
	}
	inrow += v_expand;
  }
}


/*
 * Downsample pixel values of a single component.
 * This version handles the common case of 2:1 horizontal and 1:1 vertical,
 * without smoothing.
 */

METHODDEF void
h2v1_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 outcol;
  register JSAMPROW inptr, outptr;

#ifdef DEBUG            /* for debugging pipeline controller */
  jpeg_component_info * compptr = cinfo->cur_comp_info[which_component];
  
/*******************DID NOT SUPPORT THIS ERROR******************************  
  if (output_rows != compptr->v_samp_factor ||
	  input_rows != cinfo->max_v_samp_factor ||
	  (output_cols % compptr->h_samp_factor) != 0 ||
	  (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

  for (outrow = 0; outrow < output_rows; outrow++) {
	outptr = output_data[outrow];
	inptr = input_data[outrow];
	for (outcol = 0; outcol < output_cols; outcol++) {
	  *outptr++ = (JSAMPLE) ((GETJSAMPLE(*inptr) + GETJSAMPLE(inptr[1])
				  + 1) >> 1);
	  inptr += 2;
	}
  }
}


/*
 * Downsample pixel values of a single component.
 * This version handles the standard case of 2:1 horizontal and 2:1 vertical,
 * without smoothing.
 */

METHODDEF void
h2v2_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 inrow, outrow;
  long outcol;
  register JSAMPROW inptr0, inptr1, outptr;

#ifdef DEBUG            /* for debugging pipeline controller */
  jpeg_component_info * compptr = cinfo->cur_comp_info[which_component];
  
/*************************DID NOT SUPPORT THIS ERROR************************  
  if (output_rows != compptr->v_samp_factor ||
	  input_rows != cinfo->max_v_samp_factor ||
	  (output_cols % compptr->h_samp_factor) != 0 ||
	  (input_cols % cinfo->max_h_samp_factor) != 0 ||
	  input_cols*compptr->h_samp_factor != output_cols*cinfo->max_h_samp_factor)
	ERREXIT(cinfo->emethods);   do not suppor this error 
	(cinfo->emethods, "Bogus downsample parameters");
***************************************************************************/

#endif

  inrow = 0;
  for (outrow = 0; outrow < output_rows; outrow++) {
	outptr = output_data[outrow];
	inptr0 = input_data[inrow];
	inptr1 = input_data[inrow+1];
	for (outcol = 0; outcol < output_cols; outcol++) {
	  *outptr++ = (JSAMPLE) ((GETJSAMPLE(*inptr0) + GETJSAMPLE(inptr0[1]) +
				  GETJSAMPLE(*inptr1) + GETJSAMPLE(inptr1[1])
				  + 2) >> 2);
	  inptr0 += 2; inptr1 += 2;
	}
	inrow += 2;
  }
}


/*
 * Downsample pixel values of a single component.
 * This version handles the special case of a full-size component,
 * without smoothing.
 */

METHODDEF void
fullsize_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)
{
#ifdef DEBUG            /* for debugging pipeline controller */
  
/***************************DID NOT SUPPORT THIS ERROR**********************  
  if (input_cols != output_cols || input_rows != output_rows)
	ERREXIT(cinfo->emethods);   
	(cinfo->emethods, "Pipeline controller messed up");
***************************************************************************/

#endif

  jcopy_sample_rows(input_data, 0, output_data, 0, output_rows, output_cols);
}


#ifdef INPUT_SMOOTHING_SUPPORTED

/*
 * Downsample pixel values of a single component.
 * This version handles the standard case of 2:1 horizontal and 2:1 vertical,
 * with smoothing.
 */

METHODDEF void
h2v2_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 inrow, outrow;
  long colctr;
  register JSAMPROW inptr0, inptr1, above_ptr, below_ptr, outptr;
  INT32 membersum, neighsum, memberscale, neighscale;

#ifdef DEBUG            /* for debugging pipeline controller */
  jpeg_component_info * compptr = cinfo->cur_comp_info[which_component];
  
/*************************DID NOT SUPPORT THIS ERROR************************  
  if (output_rows != compptr->v_samp_factor ||       
	  input_rows != cinfo->max_v_samp_factor ||
	  (output_cols % compptr->h_samp_factor) != 0 ||