kc3-lang/libjpeg-turbo/jcsample.c

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• Hash : bd543f03
  Author :
  Date : 1991-12-13T00:00:00
  

  The Independent JPEG Group's JPEG software v2
  

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• jcsample.c

• /*
   * jcsample.c
   *
   * Copyright (C) 1991, 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 subsampling routines.
   * These routines are invoked via the subsample and
   * subsample_init/term methods.
   */
  
  #include "jinclude.h"
  
  
  /*
   * Initialize for subsampling a scan.
   */
  
  METHODDEF void
  subsample_init (compress_info_ptr cinfo)
  {
    /* no work for now */
  }
  
  
  /*
   * Subsample pixel values of a single component.
   * This version only handles integral sampling ratios.
   */
  
  METHODDEF void
  subsample (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;
    JSAMPROW inptr, outptr;
    INT32 outvalue;
  
    /* TEMP FOR DEBUGGING PIPELINE CONTROLLER */
    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, "Bogus subsample parameters");
  
    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 < output_cols; outcol++) {
        outvalue = 0;
        for (v = 0; v < v_expand; v++) {
  	inptr = input_data[inrow+v] + (outcol*h_expand);
  	for (h = 0; h < h_expand; h++) {
  	  outvalue += (INT32) GETJSAMPLE(*inptr++);
  	}
        }
        *outptr++ = (JSAMPLE) ((outvalue + numpix2) / numpix);
      }
      inrow += v_expand;
    }
  }
  
  
  /*
   * Subsample pixel values of a single component.
   * This version handles the special case of a full-size component.
   */
  
  METHODDEF void
  fullsize_subsample (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)
  {
    if (input_cols != output_cols || input_rows != output_rows) /* DEBUG */
      ERREXIT(cinfo->emethods, "Pipeline controller messed up");
  
    jcopy_sample_rows(input_data, 0, output_data, 0, output_rows, output_cols);
  }
  
  
  /*
   * Clean up after a scan.
   */
  
  METHODDEF void
  subsample_term (compress_info_ptr cinfo)
  {
    /* no work for now */
  }
  
  
  
  /*
   * The method selection routine for subsampling.
   * Note that we must select a routine for each component.
   */
  
  GLOBAL void
  jselsubsample (compress_info_ptr cinfo)
  {
    short ci;
    jpeg_component_info * compptr;
  
    if (cinfo->CCIR601_sampling)
      ERREXIT(cinfo->emethods, "CCIR601 subsampling 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)
        cinfo->methods->subsample[ci] = fullsize_subsample;
      else if ((cinfo->max_h_samp_factor % compptr->h_samp_factor) == 0 &&
  	     (cinfo->max_v_samp_factor % compptr->v_samp_factor) == 0)
        cinfo->methods->subsample[ci] = subsample;
      else
        ERREXIT(cinfo->emethods, "Fractional subsampling not implemented yet");
    }
  
    cinfo->methods->subsample_init = subsample_init;
    cinfo->methods->subsample_term = subsample_term;
  }
  

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