2 * qscale: Quick, high-quality JPEG-to-JPEG scaler.
3 * Copyright (C) 2008 Steinar H. Gunderson <sgunderson@bigfoot.com>
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation, version 2 of the License.
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
23 #include "libqscale.h"
25 int main(int argc, char **argv)
27 /* user-settable parameters */
28 unsigned nominal_w = atoi(argv[1]);
29 unsigned nominal_h = atoi(argv[2]);
30 unsigned samp_h0 = 2, samp_v0 = 2;
31 unsigned samp_h1 = 1, samp_v1 = 1;
32 unsigned samp_h2 = 1, samp_v2 = 1;
33 unsigned jpeg_quality = 85;
36 qscale_img *img = qscale_load_jpeg_from_stdio(stdin);
37 qscale_img *scaled = qscale_scale(img, nominal_w, nominal_h, samp_h0, samp_v0, samp_h1, samp_v1, samp_h2, samp_v2, LANCZOS);
40 struct jpeg_compress_struct cinfo;
41 struct jpeg_error_mgr jerr;
42 cinfo.err = jpeg_std_error(&jerr);
43 jpeg_create_compress(&cinfo);
44 jpeg_stdio_dest(&cinfo, stdout);
45 cinfo.input_components = 3;
46 jpeg_set_defaults(&cinfo);
47 jpeg_set_quality(&cinfo, jpeg_quality, FALSE);
48 cinfo.image_width = nominal_w;
49 cinfo.image_height = nominal_h;
50 cinfo.raw_data_in = TRUE;
51 jpeg_set_colorspace(&cinfo, JCS_YCbCr);
52 cinfo.comp_info[0].h_samp_factor = samp_h0;
53 cinfo.comp_info[0].v_samp_factor = samp_v0;
54 cinfo.comp_info[1].h_samp_factor = samp_h1;
55 cinfo.comp_info[1].v_samp_factor = samp_v1;
56 cinfo.comp_info[2].h_samp_factor = samp_h2;
57 cinfo.comp_info[2].v_samp_factor = samp_v2;
58 jpeg_start_compress(&cinfo, TRUE);
60 unsigned dstride0 = (scaled->w0 + DCTSIZE-1) & ~(DCTSIZE-1);
61 unsigned dstride1 = (scaled->w1 + DCTSIZE-1) & ~(DCTSIZE-1);
62 unsigned dstride2 = (scaled->w2 + DCTSIZE-1) & ~(DCTSIZE-1);
66 while (total_lines < cinfo.comp_info[0].height_in_blocks * DCTSIZE) {
67 unsigned max_lines = cinfo.max_v_samp_factor * DCTSIZE;
69 JSAMPROW y_row_ptrs[max_lines];
70 JSAMPROW cb_row_ptrs[max_lines];
71 JSAMPROW cr_row_ptrs[max_lines];
72 JSAMPROW* ptrs[] = { y_row_ptrs, cb_row_ptrs, cr_row_ptrs };
75 for (i = 0; i < max_lines; ++i) {
76 /* simple edge extension */
77 int yline = i + blocks*DCTSIZE*cinfo.comp_info[0].v_samp_factor;
78 if (yline > scaled->h0 - 1)
79 yline = scaled->h0 - 1;
81 int cbline = i + blocks*DCTSIZE*cinfo.comp_info[1].v_samp_factor;
82 if (cbline > scaled->h1 - 1)
83 cbline = scaled->h2 - 1;
85 int crline = i + blocks*DCTSIZE*cinfo.comp_info[2].v_samp_factor;
86 if (crline > scaled->h2 - 1)
87 crline = scaled->h2 - 1;
89 y_row_ptrs[i] = scaled->data_y + yline * dstride0;
90 cb_row_ptrs[i] = scaled->data_cb + cbline * dstride1;
91 cr_row_ptrs[i] = scaled->data_cr + crline * dstride2;
94 total_lines += max_lines;
97 jpeg_write_raw_data(&cinfo, ptrs, max_lines);
99 jpeg_finish_compress(&cinfo);
100 jpeg_destroy_compress(&cinfo);