1 /*
2 * write-exif.c
3 *
4 * Placed into the public domain by Daniel Fandrich
5 *
6 * Create a new EXIF data block and write it into a JPEG image file.
7 *
8 * The JPEG image data used in this example is fixed and is guaranteed not
9 * to contain an EXIF tag block already, so it is easy to precompute where
10 * in the file the EXIF data should be. In real life, a library like
11 * libjpeg (included with the exif command-line tool source code) would
12 * be used to write to an existing JPEG file.
13 */
14
15 #include <stdio.h>
16 #include <stdlib.h>
17 #include <string.h>
18 #include <assert.h>
19 #include <libexif/exif-data.h>
20
21 /* this file will be unilaterally overwritten */
22 #define FILE_NAME "write-exif.jpg"
23
24 /* raw JPEG image data */
25 static const unsigned char image_jpg[] = {
26 0xff, 0xd8, 0xff, 0xe0, 0x00, 0x10, 0x4a, 0x46, 0x49, 0x46, 0x00, 0x01,
27 0x01, 0x01, 0x00, 0x48, 0x00, 0x48, 0x00, 0x00, 0xff, 0xdb, 0x00, 0x43,
28 0x00, 0x14, 0x0e, 0x0f, 0x12, 0x0f, 0x0d, 0x14, 0x12, 0x10, 0x12, 0x17,
29 0x15, 0x14, 0x18, 0x1e, 0x32, 0x21, 0x1e, 0x1c, 0x1c, 0x1e, 0x3d, 0x2c,
30 0x2e, 0x24, 0x32, 0x49, 0x40, 0x4c, 0x4b, 0x47, 0x40, 0x46, 0x45, 0x50,
31 0x5a, 0x73, 0x62, 0x50, 0x55, 0x6d, 0x56, 0x45, 0x46, 0x64, 0x88, 0x65,
32 0x6d, 0x77, 0x7b, 0x81, 0x82, 0x81, 0x4e, 0x60, 0x8d, 0x97, 0x8c, 0x7d,
33 0x96, 0x73, 0x7e, 0x81, 0x7c, 0xff, 0xc0, 0x00, 0x0b, 0x08, 0x00, 0x40,
34 0x00, 0x40, 0x01, 0x01, 0x11, 0x00, 0xff, 0xc4, 0x00, 0x1b, 0x00, 0x00,
35 0x03, 0x01, 0x01, 0x01, 0x01, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
36 0x00, 0x00, 0x00, 0x00, 0x05, 0x06, 0x04, 0x03, 0x07, 0x02, 0x01, 0xff,
37 0xc4, 0x00, 0x2f, 0x10, 0x00, 0x01, 0x03, 0x03, 0x02, 0x05, 0x03, 0x03,
38 0x03, 0x05, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x02, 0x03, 0x11,
39 0x00, 0x04, 0x05, 0x21, 0x31, 0x06, 0x12, 0x41, 0x51, 0x81, 0x61, 0x71,
40 0x91, 0x13, 0x32, 0xa1, 0x14, 0x22, 0xc1, 0x15, 0x23, 0x52, 0xd1, 0xf0,
41 0xff, 0xda, 0x00, 0x08, 0x01, 0x01, 0x00, 0x00, 0x3f, 0x00, 0xb3, 0xa2,
42 0x8a, 0x28, 0xa2, 0x8a, 0x28, 0xa2, 0x97, 0x64, 0x72, 0xd6, 0x58, 0xd4,
43 0x8f, 0xd5, 0x3d, 0xca, 0xa5, 0x7d, 0xa8, 0x4e, 0xaa, 0x3e, 0xb0, 0x3a,
44 0x7a, 0x9d, 0x2b, 0x2d, 0x87, 0x13, 0xe3, 0xaf, 0x9f, 0x0c, 0xb6, 0xb5,
45 0xb6, 0xe2, 0xb4, 0x48, 0x71, 0x30, 0x14, 0x7b, 0x02, 0x09, 0x14, 0xee,
46 0x94, 0x64, 0x38, 0x87, 0x1f, 0x8d, 0x5f, 0xd3, 0x7d, 0xe2, 0xa7, 0x46,
47 0xe8, 0x6c, 0x49, 0x1e, 0xfd, 0x07, 0xb1, 0x33, 0x5f, 0xb8, 0xdc, 0xf5,
48 0x96, 0x51, 0x7c, 0x96, 0xee, 0x14, 0xba, 0x04, 0xf2, 0x2c, 0x42, 0xa3,
49 0xd3, 0x70, 0x7c, 0x1a, 0x6d, 0x45, 0x2c, 0xcd, 0xe5, 0x11, 0x89, 0xb1,
50 0x5b, 0xc4, 0x02, 0xe1, 0xd1, 0xb4, 0xcf, 0xdc, 0xa3, 0xfc, 0x0d, 0xcd,
51 0x41, 0xde, 0xe3, 0xb2, 0x2e, 0xda, 0x1c, 0xbd, 0xe2, 0x4a, 0x90, 0xe9,
52 0x04, 0x95, 0x2b, 0xf7, 0x41, 0xd0, 0x18, 0xe8, 0x36, 0x03, 0xc6, 0x91,
53 0x4a, 0x81, 0x20, 0x82, 0x24, 0x10, 0x66, 0x45, 0x5a, 0xdd, 0xf1, 0x32,
54 0xff, 0x00, 0xa2, 0x5a, 0x8b, 0x62, 0x57, 0x7d, 0x70, 0x80, 0x93, 0x1a,
55 0x94, 0x10, 0x79, 0x4a, 0xa3, 0xb9, 0x20, 0xc0, 0xf3, 0xd3, 0x55, 0x59,
56 0x4e, 0x1c, 0x7a, 0xc7, 0x12, 0x9b, 0xc7, 0x94, 0xa7, 0x2e, 0x14, 0xa9,
57 0x74, 0x0d, 0x42, 0x01, 0x04, 0xc9, 0x3b, 0x93, 0x30, 0x09, 0xdb, 0x5f,
58 0x35, 0x9b, 0x85, 0xad, 0xde, 0x7f, 0x39, 0x6e, 0xa6, 0x82, 0xa1, 0xa5,
59 0x73, 0x2d, 0x40, 0x68, 0x13, 0x06, 0x67, 0xdf, 0x6f, 0x35, 0xe9, 0xb4,
60 0x52, 0x4c, 0xbe, 0x0c, 0x65, 0x72, 0x16, 0xcf, 0x3a, 0xff, 0x00, 0xf6,
61 0x5a, 0xd1, 0x4d, 0x11, 0xa1, 0x13, 0x26, 0x0f, 0x73, 0x00, 0x1f, 0x41,
62 0x5b, 0x72, 0xd6, 0xa2, 0xeb, 0x15, 0x73, 0x6e, 0x13, 0xf7, 0x36, 0x42,
63 0x40, 0xee, 0x04, 0x8f, 0xc8, 0x15, 0xe4, 0xf5, 0x59, 0xc1, 0x16, 0x0d,
64 0x3d, 0x70, 0xed, 0xdb, 0x84, 0x29, 0x6c, 0x40, 0x42, 0x3b, 0x13, 0x3f,
65 0xb8, 0xfc, 0x10, 0x3c, 0xd5, 0xc1, 0x00, 0x88, 0x22, 0x41, 0xef, 0x5f,
66 0x0d, 0xb4, 0x86, 0x81, 0x0d, 0xa1, 0x28, 0x07, 0x52, 0x12, 0x00, 0x06,
67 0xba, 0xd1, 0x45, 0x71, 0xb8, 0xb8, 0x6e, 0xd9, 0x85, 0xbc, 0xf2, 0xb9,
68 0x5b, 0x40, 0x25, 0x47, 0xb0, 0xaf, 0x24, 0x79, 0x48, 0x53, 0xce, 0x29,
69 0xb4, 0x94, 0xa0, 0xa8, 0x94, 0xa7, 0xb0, 0x27, 0x41, 0xf1, 0x54, 0x9c,
70 0x09, 0x71, 0xc9, 0x92, 0x7d, 0x82, 0x74, 0x75, 0xa9, 0x1e, 0xa5, 0x27,
71 0xfd, 0x13, 0x55, 0xd9, 0x3c, 0x83, 0x38, 0xbb, 0x45, 0x5c, 0xbf, 0x3c,
72 0xa1, 0x40, 0x40, 0x02, 0x54, 0x4f, 0x41, 0x3e, 0x4f, 0x83, 0x5a, 0x2d,
73 0xae, 0x1b, 0xba, 0xb7, 0x6d, 0xf6, 0x89, 0x28, 0x71, 0x21, 0x49, 0x24,
74 0x41, 0x83, 0xe9, 0x5d, 0xe9, 0x3f, 0x12, 0x64, 0x97, 0x8b, 0xc6, 0x17,
75 0x59, 0x03, 0xea, 0xa9, 0x61, 0x08, 0x24, 0x48, 0x04, 0xc9, 0x9f, 0x80,
76 0x6a, 0x4b, 0x17, 0xc4, 0xd7, 0xac, 0xdf, 0x36, 0xab, 0xbb, 0x85, 0x39,
77 0x6e, 0xb5, 0x00, 0xe0, 0x50, 0x06, 0x01, 0x3a, 0x91, 0x02, 0x44, 0x6f,
78 0x02, 0xb7, 0x65, 0xb2, 0x0e, 0x71, 0x25, 0xf3, 0x58, 0xdc, 0x72, 0x8f,
79 0xe9, 0xc1, 0xe6, 0x52, 0xe0, 0xc2, 0xa3, 0x72, 0x46, 0xe0, 0x0e, 0x83,
80 0xa9, 0xf1, 0x4b, 0x38, 0x9f, 0x16, 0xde, 0x2e, 0xfd, 0xa4, 0x32, 0x92,
81 0x1a, 0x5b, 0x40, 0x83, 0xdc, 0x8d, 0x0f, 0x9d, 0x01, 0x3e, 0xf5, 0x83,
82 0x17, 0x7a, 0xac, 0x76, 0x41, 0x9b, 0xa4, 0xa7, 0x9b, 0xe9, 0xab, 0x51,
83 0x31, 0x20, 0x82, 0x08, 0xf8, 0x34, 0xf9, 0xdb, 0x97, 0xb8, 0xb7, 0x2c,
84 0xcd, 0xba, 0x12, 0xa6, 0xec, 0xda, 0x3c, 0xca, 0x13, 0x24, 0x0e, 0xa4,
85 0x91, 0xa4, 0x9d, 0x87, 0x69, 0xf7, 0xab, 0x74, 0x21, 0x2d, 0xa1, 0x28,
86 0x4a, 0x42, 0x52, 0x90, 0x02, 0x40, 0xd8, 0x01, 0xb0, 0xae, 0x95, 0x87,
87 0x29, 0x8f, 0x6f, 0x27, 0x64, 0xe5, 0xb3, 0xc4, 0x80, 0xa8, 0x29, 0x50,
88 0xdd, 0x24, 0x6c, 0x47, 0xfd, 0xd4, 0xd4, 0x92, 0x78, 0x1e, 0xef, 0xeb,
89 0x42, 0xae, 0x98, 0x0d, 0x7f, 0x90, 0x0a, 0x27, 0xe2, 0x00, 0xfc, 0xd5,
90 0x4e, 0x27, 0x11, 0x6d, 0x89, 0x60, 0xb7, 0x6e, 0x92, 0x54, 0xa8, 0xe6,
91 0x71, 0x5b, 0xa8, 0xff, 0x00, 0x03, 0xd2, 0xbe, 0x73, 0x38, 0x86, 0x72,
92 0xf6, 0xc1, 0xb7, 0x4f, 0x2a, 0xd1, 0x25, 0x0e, 0x01, 0x25, 0x27, 0xae,
93 0x9d, 0x41, 0xed, 0xed, 0x52, 0xe8, 0xe0, 0x7b, 0xcf, 0xab, 0x0e, 0x5d,
94 0x30, 0x96, 0xe7, 0xee, 0x4f, 0x31, 0x57, 0xc1, 0x00, 0x7e, 0x6a, 0xaf,
95 0x15, 0x8b, 0x63, 0x17, 0x6e, 0x1a, 0x61, 0x24, 0x92, 0x65, 0x6b, 0x3b,
96 0xa8, 0xf7, 0x3e, 0x9d, 0x87, 0x4a, 0x63, 0x45, 0x14, 0x51, 0x45, 0x14,
97 0x51, 0x45, 0x7f, 0xff, 0xd9
98 };
99
100 /* length of data in image_jpg */
101 static const unsigned int image_jpg_len = sizeof(image_jpg);
102
103 /* dimensions of image */
104 static const unsigned int image_jpg_x = 64;
105 static const unsigned int image_jpg_y = 64;
106
107 /* start of JPEG image data section */
108 static const unsigned int image_data_offset = 20;
109 #define image_data_len (image_jpg_len - image_data_offset)
110
111 /* raw EXIF header data */
112 static const unsigned char exif_header[] = {
113 0xff, 0xd8, 0xff, 0xe1
114 };
115 /* length of data in exif_header */
116 static const unsigned int exif_header_len = sizeof(exif_header);
117
118 /* byte order to use in the EXIF block */
119 #define FILE_BYTE_ORDER EXIF_BYTE_ORDER_INTEL
120
121 /* comment to write into the EXIF block */
122 #define FILE_COMMENT "libexif demonstration image"
123
124 /* special header required for EXIF_TAG_USER_COMMENT */
125 #define ASCII_COMMENT "ASCII\0\0\0"
126
127
128 /* Get an existing tag, or create one if it doesn't exist */
init_tag(ExifData * exif,ExifIfd ifd,ExifTag tag)129 static ExifEntry *init_tag(ExifData *exif, ExifIfd ifd, ExifTag tag)
130 {
131 ExifEntry *entry;
132 /* Return an existing tag if one exists */
133 if (!((entry = exif_content_get_entry (exif->ifd[ifd], tag)))) {
134 /* Allocate a new entry */
135 entry = exif_entry_new ();
136 assert(entry != NULL); /* catch an out of memory condition */
137 entry->tag = tag; /* tag must be set before calling
138 exif_content_add_entry */
139
140 /* Attach the ExifEntry to an IFD */
141 exif_content_add_entry (exif->ifd[ifd], entry);
142
143 /* Allocate memory for the entry and fill with default data */
144 exif_entry_initialize (entry, tag);
145
146 /* Ownership of the ExifEntry has now been passed to the IFD.
147 * One must be very careful in accessing a structure after
148 * unref'ing it; in this case, we know "entry" won't be freed
149 * because the reference count was bumped when it was added to
150 * the IFD.
151 */
152 exif_entry_unref(entry);
153 }
154 return entry;
155 }
156
157 /* Create a brand-new tag with a data field of the given length, in the
158 * given IFD. This is needed when exif_entry_initialize() isn't able to create
159 * this type of tag itself, or the default data length it creates isn't the
160 * correct length.
161 */
create_tag(ExifData * exif,ExifIfd ifd,ExifTag tag,size_t len)162 static ExifEntry *create_tag(ExifData *exif, ExifIfd ifd, ExifTag tag, size_t len)
163 {
164 void *buf;
165 ExifEntry *entry;
166
167 /* Create a memory allocator to manage this ExifEntry */
168 ExifMem *mem = exif_mem_new_default();
169 assert(mem != NULL); /* catch an out of memory condition */
170
171 /* Create a new ExifEntry using our allocator */
172 entry = exif_entry_new_mem (mem);
173 assert(entry != NULL);
174
175 /* Allocate memory to use for holding the tag data */
176 buf = exif_mem_alloc(mem, len);
177 assert(buf != NULL);
178
179 /* Fill in the entry */
180 entry->data = buf;
181 entry->size = len;
182 entry->tag = tag;
183 entry->components = len;
184 entry->format = EXIF_FORMAT_UNDEFINED;
185
186 /* Attach the ExifEntry to an IFD */
187 exif_content_add_entry (exif->ifd[ifd], entry);
188
189 /* The ExifMem and ExifEntry are now owned elsewhere */
190 exif_mem_unref(mem);
191 exif_entry_unref(entry);
192
193 return entry;
194 }
195
main(int argc,char ** argv)196 int main(int argc, char **argv)
197 {
198 int rc = 1;
199 FILE *f;
200 unsigned char *exif_data;
201 unsigned int exif_data_len;
202 ExifEntry *entry;
203 ExifData *exif = exif_data_new();
204 if (!exif) {
205 fprintf(stderr, "Out of memory\n");
206 return 2;
207 }
208
209 /* Set the image options */
210 exif_data_set_option(exif, EXIF_DATA_OPTION_FOLLOW_SPECIFICATION);
211 exif_data_set_data_type(exif, EXIF_DATA_TYPE_COMPRESSED);
212 exif_data_set_byte_order(exif, FILE_BYTE_ORDER);
213
214 /* Create the mandatory EXIF fields with default data */
215 exif_data_fix(exif);
216
217 /* All these tags are created with default values by exif_data_fix() */
218 /* Change the data to the correct values for this image. */
219 entry = init_tag(exif, EXIF_IFD_EXIF, EXIF_TAG_PIXEL_X_DIMENSION);
220 exif_set_long(entry->data, FILE_BYTE_ORDER, image_jpg_x);
221
222 entry = init_tag(exif, EXIF_IFD_EXIF, EXIF_TAG_PIXEL_Y_DIMENSION);
223 exif_set_long(entry->data, FILE_BYTE_ORDER, image_jpg_y);
224
225 entry = init_tag(exif, EXIF_IFD_EXIF, EXIF_TAG_COLOR_SPACE);
226 exif_set_short(entry->data, FILE_BYTE_ORDER, 1);
227
228 /* Create a EXIF_TAG_USER_COMMENT tag. This one must be handled
229 * differently because that tag isn't automatically created and
230 * allocated by exif_data_fix(), nor can it be created using
231 * exif_entry_initialize() so it must be explicitly allocated here.
232 */
233 entry = create_tag(exif, EXIF_IFD_EXIF, EXIF_TAG_USER_COMMENT,
234 sizeof(ASCII_COMMENT) + sizeof(FILE_COMMENT) - 2);
235 /* Write the special header needed for a comment tag */
236 memcpy(entry->data, ASCII_COMMENT, sizeof(ASCII_COMMENT)-1);
237 /* Write the actual comment text, without the trailing NUL character */
238 memcpy(entry->data+8, FILE_COMMENT, sizeof(FILE_COMMENT)-1);
239 /* create_tag() happens to set the format and components correctly for
240 * EXIF_TAG_USER_COMMENT, so there is nothing more to do. */
241
242 /* Create a EXIF_TAG_SUBJECT_AREA tag */
243 entry = create_tag(exif, EXIF_IFD_EXIF, EXIF_TAG_SUBJECT_AREA,
244 4 * exif_format_get_size(EXIF_FORMAT_SHORT));
245 entry->format = EXIF_FORMAT_SHORT;
246 entry->components = 4;
247 exif_set_short(entry->data, FILE_BYTE_ORDER, image_jpg_x / 2);
248 exif_set_short(entry->data+2, FILE_BYTE_ORDER, image_jpg_y / 2);
249 exif_set_short(entry->data+4, FILE_BYTE_ORDER, image_jpg_x);
250 exif_set_short(entry->data+6, FILE_BYTE_ORDER, image_jpg_y);
251
252 /* Get a pointer to the EXIF data block we just created */
253 exif_data_save_data(exif, &exif_data, &exif_data_len);
254 assert(exif_data != NULL);
255
256 f = fopen(FILE_NAME, "wb");
257 if (!f) {
258 fprintf(stderr, "Error creating file %s\n", FILE_NAME);
259 exif_data_unref(exif);
260 return rc;
261 }
262 /* Write EXIF header */
263 if (fwrite(exif_header, exif_header_len, 1, f) != 1) {
264 fprintf(stderr, "Error writing to file %s\n", FILE_NAME);
265 goto errout;
266 }
267 /* Write EXIF block length in big-endian order */
268 if (fputc((exif_data_len+2) >> 8, f) < 0) {
269 fprintf(stderr, "Error writing to file %s\n", FILE_NAME);
270 goto errout;
271 }
272 if (fputc((exif_data_len+2) & 0xff, f) < 0) {
273 fprintf(stderr, "Error writing to file %s\n", FILE_NAME);
274 goto errout;
275 }
276 /* Write EXIF data block */
277 if (fwrite(exif_data, exif_data_len, 1, f) != 1) {
278 fprintf(stderr, "Error writing to file %s\n", FILE_NAME);
279 goto errout;
280 }
281 /* Write JPEG image data, skipping the non-EXIF header */
282 if (fwrite(image_jpg+image_data_offset, image_data_len, 1, f) != 1) {
283 fprintf(stderr, "Error writing to file %s\n", FILE_NAME);
284 goto errout;
285 }
286 printf("Wrote file %s\n", FILE_NAME);
287 rc = 0;
288
289 errout:
290 if (fclose(f)) {
291 fprintf(stderr, "Error writing to file %s\n", FILE_NAME);
292 rc = 1;
293 }
294 /* The allocator we're using for ExifData is the standard one, so use
295 * it directly to free this pointer.
296 */
297 free(exif_data);
298 exif_data_unref(exif);
299
300 return rc;
301 }
302