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 */
25static 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 */
101static const unsigned int image_jpg_len = sizeof(image_jpg);
102
103/* dimensions of image */
104static const unsigned int image_jpg_x = 64;
105static const unsigned int image_jpg_y = 64;
106
107/* start of JPEG image data section */
108static const unsigned int image_data_offset = 20;
109#define image_data_len (image_jpg_len - image_data_offset)
110
111/* raw EXIF header data */
112static const unsigned char exif_header[] = {
113  0xff, 0xd8, 0xff, 0xe1
114};
115/* length of data in exif_header */
116static 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 */
129static 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 */
162static 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
196int 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
289errout:
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