compiler/libjpeg/main/jcscale.c

   1 /*
   2     $Id$
   3 */
   4
   5 /*
   6  * jcscale.c
   7  *
   8  * Copyright (C) 1998, Thomas G. Lane.
   9  * This file is part of the Independent JPEG Group's software.
  10  * For conditions of distribution and use, see the accompanying README file.
  11  *
  12  * This file contains sample downscaling by 2^Pt for lossless JPEG.
  13  */
  14
  15 #define JPEG_INTERNALS
  16 #include "jinclude.h"
  17 #include "jpeglib.h"
  18 #include "jlossls.h"            /* Private declarations for lossless codec */
  19
  20
  21 #ifdef C_LOSSLESS_SUPPORTED
  22
  23 METHODDEF(void)
  24 simple_downscale(j_compress_ptr cinfo,
  25                  JSAMPROW input_buf, JSAMPROW output_buf, JDIMENSION width)
  26 {
  27   j_lossless_c_ptr losslsc = (j_lossless_c_ptr) cinfo->codec;
  28   int xindex;
  29
  30   for (xindex = 0; xindex < width; xindex++)
  31     output_buf[xindex] = (JSAMPLE) RIGHT_SHIFT(GETJSAMPLE(input_buf[xindex]),
  32                                                cinfo->Al);
  33 }
  34
  35
  36 METHODDEF(void)
  37 noscale(j_compress_ptr cinfo,
  38         JSAMPROW input_buf, JSAMPROW output_buf, JDIMENSION width)
  39 {
  40   MEMCOPY(output_buf, input_buf, width * SIZEOF(JSAMPLE));
  41   return;
  42 }
  43
  44
  45 METHODDEF(void)
  46 scaler_start_pass (j_compress_ptr cinfo)
  47 {
  48   j_lossless_c_ptr losslsc = (j_lossless_c_ptr) cinfo->codec;
  49
  50   /* Set scaler function based on Pt */
  51   if (cinfo->Al)
  52     losslsc->scaler_scale = simple_downscale;
  53   else
  54     losslsc->scaler_scale = noscale;
  55 }
  56
  57
  58 JGLOBAL(void)
  59 jinit_c_scaler (j_compress_ptr cinfo)
  60 {
  61   j_lossless_c_ptr losslsc = (j_lossless_c_ptr) cinfo->codec;
  62
  63   losslsc->scaler_start_pass = scaler_start_pass;
  64 }
  65
  66 #endif /* C_LOSSLESS_SUPPORTED */