1 /** \file test-extract.c
2 * \brief Extract EXIF data from a file and write it to another file.
3 *
4 * Copyright (C) 2019 Dan Fandrich <dan@coneharvesters.com>
5 *
6 * This library is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation; either
9 * version 2 of the License, or (at your option) any later version.
10 *
11 * This library is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Lesser General Public License for more details.
15 *
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with this library; if not, write to the
18 * Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
19 * Boston, MA 02110-1301 USA.
20 *
21 * SPDX-License-Identifier: LGPL-2.0-or-later
22 */
23
24 #include "libexif/exif-data.h"
25
26 #include <string.h>
27 #include <stdio.h>
28 #include <stdlib.h>
29
30
31 static const unsigned char header[4] = {'\xff', '\xd8', '\xff', '\xe1'};
32
main(const int argc,const char * argv[])33 int main(const int argc, const char *argv[])
34 {
35 int first = 1;
36 const char *fn = "input.jpg";
37 const char *outfn = "output.exif";
38 ExifData *d;
39 unsigned char *buf;
40 unsigned int len;
41 FILE *f;
42 unsigned char lenbuf[2];
43
44 if (argc > 1 && !strcmp(argv[1], "-o")) {
45 outfn = argv[2];
46 first += 2;
47 }
48 if (argc > first) {
49 fn = argv[first];
50 ++first;
51 }
52 if (argc > first) {
53 fprintf (stderr, "Too many arguments\n");
54 return 1;
55 }
56
57 d = exif_data_new_from_file(fn);
58 if (!d) {
59 fprintf (stderr, "Could not load data from '%s'!\n", fn);
60 return 1;
61 }
62
63 exif_data_save_data(d, &buf, &len);
64 exif_data_unref(d);
65
66 if (!buf) {
67 fprintf (stderr, "Could not extract EXIF data!\n");
68 return 2;
69 }
70
71 f = fopen(outfn, "wb");
72 if (!f) {
73 fprintf (stderr, "Could not open '%s' for writing!\n", outfn);
74 return 1;
75 }
76 /* Write EXIF with headers and length. */
77 if (fwrite(header, 1, sizeof(header), f) != sizeof(header)) {
78 fprintf (stderr, "Could not write to '%s'!\n", outfn);
79 return 3;
80 }
81 /*
82 * FIXME: The buffer from exif_data_save_data() seems to contain extra 0xffd8
83 * 0xffd9 JPEG markers at the end that I wasn't expecting, making the length
84 * seem too long. Should those markers really be included?
85 */
86 exif_set_short(lenbuf, EXIF_BYTE_ORDER_MOTOROLA, len);
87 if (fwrite(lenbuf, 1, 2, f) != 2) {
88 fprintf (stderr, "Could not write to '%s'!\n", outfn);
89 return 3;
90 }
91 if (fwrite(buf, 1, len, f) != len) {
92 fprintf (stderr, "Could not write to '%s'!\n", outfn);
93 return 3;
94 }
95 if (fclose(f) != 0) {
96 fprintf (stderr, "Could not close '%s'!\n", outfn);
97 return 3;
98 }
99 free(buf);
100 fprintf (stderr, "Wrote EXIF data to '%s'\n", outfn);
101
102 return 0;
103 }
104