1 /*
2 * jcscale.c
3 *
4 * Copyright (C) 1998, Thomas G. Lane.
5 * This file is part of the Independent JPEG Group's software.
6 * For conditions of distribution and use, see the accompanying README file.
7 *
8 * This file contains sample downscaling by 2^Pt for lossless JPEG.
9 */
10
11 #define JPEG_INTERNALS
12 #include "jinclude16.h"
13 #include "jpeglib16.h"
14 #include "jlossls16.h" /* Private declarations for lossless codec */
15
16
17 #ifdef C_LOSSLESS_SUPPORTED
18
19 METHODDEF(void)
simple_downscale(j_compress_ptr cinfo,const JSAMPROW input_buf,JSAMPROW output_buf,JDIMENSION width)20 simple_downscale(j_compress_ptr cinfo,
21 const JSAMPROW input_buf, JSAMPROW output_buf, JDIMENSION width)
22 {
23 /* j_lossless_c_ptr losslsc = (j_lossless_c_ptr) cinfo->codec; */
24 unsigned int xindex;
25 SHIFT_TEMPS
26
27 for (xindex = 0; xindex < width; xindex++)
28 output_buf[xindex] = (JSAMPLE) RIGHT_SHIFT(GETJSAMPLE(input_buf[xindex]),
29 cinfo->Al);
30 }
31
32
33 METHODDEF(void)
noscale(j_compress_ptr cinfo,JSAMPROW input_buf,JSAMPROW output_buf,JDIMENSION width)34 noscale(j_compress_ptr cinfo,
35 JSAMPROW input_buf, JSAMPROW output_buf, JDIMENSION width)
36 {
37 MEMCOPY(output_buf, input_buf, width * SIZEOF(JSAMPLE));
38 return;
39 }
40
41
42 METHODDEF(void)
scaler_start_pass(j_compress_ptr cinfo)43 scaler_start_pass (j_compress_ptr cinfo)
44 {
45 j_lossless_c_ptr losslsc = (j_lossless_c_ptr) cinfo->codec;
46
47 /* Set scaler function based on Pt */
48 if (cinfo->Al)
49 losslsc->scaler_scale = simple_downscale;
50 else
51 losslsc->scaler_scale = noscale;
52 }
53
54
55 GLOBAL(void)
jinit_c_scaler(j_compress_ptr cinfo)56 jinit_c_scaler (j_compress_ptr cinfo)
57 {
58 j_lossless_c_ptr losslsc = (j_lossless_c_ptr) cinfo->codec;
59
60 losslsc->scaler_start_pass = scaler_start_pass;
61 }
62
63 #endif /* C_LOSSLESS_SUPPORTED */
64