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 */ 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 */ 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 } 195 196 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
