diff options
Diffstat (limited to 'contrib/examples/write-exif.c')
| -rw-r--r-- | contrib/examples/write-exif.c | 301 |
1 files changed, 301 insertions, 0 deletions
diff --git a/contrib/examples/write-exif.c b/contrib/examples/write-exif.c new file mode 100644 index 0000000..894cdb6 --- /dev/null +++ b/contrib/examples/write-exif.c @@ -0,0 +1,301 @@ +/* + * write-exif.c + * + * Placed into the public domain by Daniel Fandrich + * + * Create a new EXIF data block and write it into a JPEG image file. + * + * The JPEG image data used in this example is fixed and is guaranteed not + * to contain an EXIF tag block already, so it is easy to precompute where + * in the file the EXIF data should be. In real life, a library like + * libjpeg (included with the exif command-line tool source code) would + * be used to write to an existing JPEG file. + */ + +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <assert.h> +#include <libexif/exif-data.h> + +/* this file will be unilaterally overwritten */ +#define FILE_NAME "write-exif.jpg" + +/* raw JPEG image data */ +static const unsigned char image_jpg[] = { + 0xff, 0xd8, 0xff, 0xe0, 0x00, 0x10, 0x4a, 0x46, 0x49, 0x46, 0x00, 0x01, + 0x01, 0x01, 0x00, 0x48, 0x00, 0x48, 0x00, 0x00, 0xff, 0xdb, 0x00, 0x43, + 0x00, 0x14, 0x0e, 0x0f, 0x12, 0x0f, 0x0d, 0x14, 0x12, 0x10, 0x12, 0x17, + 0x15, 0x14, 0x18, 0x1e, 0x32, 0x21, 0x1e, 0x1c, 0x1c, 0x1e, 0x3d, 0x2c, + 0x2e, 0x24, 0x32, 0x49, 0x40, 0x4c, 0x4b, 0x47, 0x40, 0x46, 0x45, 0x50, + 0x5a, 0x73, 0x62, 0x50, 0x55, 0x6d, 0x56, 0x45, 0x46, 0x64, 0x88, 0x65, + 0x6d, 0x77, 0x7b, 0x81, 0x82, 0x81, 0x4e, 0x60, 0x8d, 0x97, 0x8c, 0x7d, + 0x96, 0x73, 0x7e, 0x81, 0x7c, 0xff, 0xc0, 0x00, 0x0b, 0x08, 0x00, 0x40, + 0x00, 0x40, 0x01, 0x01, 0x11, 0x00, 0xff, 0xc4, 0x00, 0x1b, 0x00, 0x00, + 0x03, 0x01, 0x01, 0x01, 0x01, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, + 0x00, 0x00, 0x00, 0x00, 0x05, 0x06, 0x04, 0x03, 0x07, 0x02, 0x01, 0xff, + 0xc4, 0x00, 0x2f, 0x10, 0x00, 0x01, 0x03, 0x03, 0x02, 0x05, 0x03, 0x03, + 0x03, 0x05, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x02, 0x03, 0x11, + 0x00, 0x04, 0x05, 0x21, 0x31, 0x06, 0x12, 0x41, 0x51, 0x81, 0x61, 0x71, + 0x91, 0x13, 0x32, 0xa1, 0x14, 0x22, 0xc1, 0x15, 0x23, 0x52, 0xd1, 0xf0, + 0xff, 0xda, 0x00, 0x08, 0x01, 0x01, 0x00, 0x00, 0x3f, 0x00, 0xb3, 0xa2, + 0x8a, 0x28, 0xa2, 0x8a, 0x28, 0xa2, 0x97, 0x64, 0x72, 0xd6, 0x58, 0xd4, + 0x8f, 0xd5, 0x3d, 0xca, 0xa5, 0x7d, 0xa8, 0x4e, 0xaa, 0x3e, 0xb0, 0x3a, + 0x7a, 0x9d, 0x2b, 0x2d, 0x87, 0x13, 0xe3, 0xaf, 0x9f, 0x0c, 0xb6, 0xb5, + 0xb6, 0xe2, 0xb4, 0x48, 0x71, 0x30, 0x14, 0x7b, 0x02, 0x09, 0x14, 0xee, + 0x94, 0x64, 0x38, 0x87, 0x1f, 0x8d, 0x5f, 0xd3, 0x7d, 0xe2, 0xa7, 0x46, + 0xe8, 0x6c, 0x49, 0x1e, 0xfd, 0x07, 0xb1, 0x33, 0x5f, 0xb8, 0xdc, 0xf5, + 0x96, 0x51, 0x7c, 0x96, 0xee, 0x14, 0xba, 0x04, 0xf2, 0x2c, 0x42, 0xa3, + 0xd3, 0x70, 0x7c, 0x1a, 0x6d, 0x45, 0x2c, 0xcd, 0xe5, 0x11, 0x89, 0xb1, + 0x5b, 0xc4, 0x02, 0xe1, 0xd1, 0xb4, 0xcf, 0xdc, 0xa3, 0xfc, 0x0d, 0xcd, + 0x41, 0xde, 0xe3, 0xb2, 0x2e, 0xda, 0x1c, 0xbd, 0xe2, 0x4a, 0x90, 0xe9, + 0x04, 0x95, 0x2b, 0xf7, 0x41, 0xd0, 0x18, 0xe8, 0x36, 0x03, 0xc6, 0x91, + 0x4a, 0x81, 0x20, 0x82, 0x24, 0x10, 0x66, 0x45, 0x5a, 0xdd, 0xf1, 0x32, + 0xff, 0x00, 0xa2, 0x5a, 0x8b, 0x62, 0x57, 0x7d, 0x70, 0x80, 0x93, 0x1a, + 0x94, 0x10, 0x79, 0x4a, 0xa3, 0xb9, 0x20, 0xc0, 0xf3, 0xd3, 0x55, 0x59, + 0x4e, 0x1c, 0x7a, 0xc7, 0x12, 0x9b, 0xc7, 0x94, 0xa7, 0x2e, 0x14, 0xa9, + 0x74, 0x0d, 0x42, 0x01, 0x04, 0xc9, 0x3b, 0x93, 0x30, 0x09, 0xdb, 0x5f, + 0x35, 0x9b, 0x85, 0xad, 0xde, 0x7f, 0x39, 0x6e, 0xa6, 0x82, 0xa1, 0xa5, + 0x73, 0x2d, 0x40, 0x68, 0x13, 0x06, 0x67, 0xdf, 0x6f, 0x35, 0xe9, 0xb4, + 0x52, 0x4c, 0xbe, 0x0c, 0x65, 0x72, 0x16, 0xcf, 0x3a, 0xff, 0x00, 0xf6, + 0x5a, 0xd1, 0x4d, 0x11, 0xa1, 0x13, 0x26, 0x0f, 0x73, 0x00, 0x1f, 0x41, + 0x5b, 0x72, 0xd6, 0xa2, 0xeb, 0x15, 0x73, 0x6e, 0x13, 0xf7, 0x36, 0x42, + 0x40, 0xee, 0x04, 0x8f, 0xc8, 0x15, 0xe4, 0xf5, 0x59, 0xc1, 0x16, 0x0d, + 0x3d, 0x70, 0xed, 0xdb, 0x84, 0x29, 0x6c, 0x40, 0x42, 0x3b, 0x13, 0x3f, + 0xb8, 0xfc, 0x10, 0x3c, 0xd5, 0xc1, 0x00, 0x88, 0x22, 0x41, 0xef, 0x5f, + 0x0d, 0xb4, 0x86, 0x81, 0x0d, 0xa1, 0x28, 0x07, 0x52, 0x12, 0x00, 0x06, + 0xba, 0xd1, 0x45, 0x71, 0xb8, 0xb8, 0x6e, 0xd9, 0x85, 0xbc, 0xf2, 0xb9, + 0x5b, 0x40, 0x25, 0x47, 0xb0, 0xaf, 0x24, 0x79, 0x48, 0x53, 0xce, 0x29, + 0xb4, 0x94, 0xa0, 0xa8, 0x94, 0xa7, 0xb0, 0x27, 0x41, 0xf1, 0x54, 0x9c, + 0x09, 0x71, 0xc9, 0x92, 0x7d, 0x82, 0x74, 0x75, 0xa9, 0x1e, 0xa5, 0x27, + 0xfd, 0x13, 0x55, 0xd9, 0x3c, 0x83, 0x38, 0xbb, 0x45, 0x5c, 0xbf, 0x3c, + 0xa1, 0x40, 0x40, 0x02, 0x54, 0x4f, 0x41, 0x3e, 0x4f, 0x83, 0x5a, 0x2d, + 0xae, 0x1b, 0xba, 0xb7, 0x6d, 0xf6, 0x89, 0x28, 0x71, 0x21, 0x49, 0x24, + 0x41, 0x83, 0xe9, 0x5d, 0xe9, 0x3f, 0x12, 0x64, 0x97, 0x8b, 0xc6, 0x17, + 0x59, 0x03, 0xea, 0xa9, 0x61, 0x08, 0x24, 0x48, 0x04, 0xc9, 0x9f, 0x80, + 0x6a, 0x4b, 0x17, 0xc4, 0xd7, 0xac, 0xdf, 0x36, 0xab, 0xbb, 0x85, 0x39, + 0x6e, 0xb5, 0x00, 0xe0, 0x50, 0x06, 0x01, 0x3a, 0x91, 0x02, 0x44, 0x6f, + 0x02, 0xb7, 0x65, 0xb2, 0x0e, 0x71, 0x25, 0xf3, 0x58, 0xdc, 0x72, 0x8f, + 0xe9, 0xc1, 0xe6, 0x52, 0xe0, 0xc2, 0xa3, 0x72, 0x46, 0xe0, 0x0e, 0x83, + 0xa9, 0xf1, 0x4b, 0x38, 0x9f, 0x16, 0xde, 0x2e, 0xfd, 0xa4, 0x32, 0x92, + 0x1a, 0x5b, 0x40, 0x83, 0xdc, 0x8d, 0x0f, 0x9d, 0x01, 0x3e, 0xf5, 0x83, + 0x17, 0x7a, 0xac, 0x76, 0x41, 0x9b, 0xa4, 0xa7, 0x9b, 0xe9, 0xab, 0x51, + 0x31, 0x20, 0x82, 0x08, 0xf8, 0x34, 0xf9, 0xdb, 0x97, 0xb8, 0xb7, 0x2c, + 0xcd, 0xba, 0x12, 0xa6, 0xec, 0xda, 0x3c, 0xca, 0x13, 0x24, 0x0e, 0xa4, + 0x91, 0xa4, 0x9d, 0x87, 0x69, 0xf7, 0xab, 0x74, 0x21, 0x2d, 0xa1, 0x28, + 0x4a, 0x42, 0x52, 0x90, 0x02, 0x40, 0xd8, 0x01, 0xb0, 0xae, 0x95, 0x87, + 0x29, 0x8f, 0x6f, 0x27, 0x64, 0xe5, 0xb3, 0xc4, 0x80, 0xa8, 0x29, 0x50, + 0xdd, 0x24, 0x6c, 0x47, 0xfd, 0xd4, 0xd4, 0x92, 0x78, 0x1e, 0xef, 0xeb, + 0x42, 0xae, 0x98, 0x0d, 0x7f, 0x90, 0x0a, 0x27, 0xe2, 0x00, 0xfc, 0xd5, + 0x4e, 0x27, 0x11, 0x6d, 0x89, 0x60, 0xb7, 0x6e, 0x92, 0x54, 0xa8, 0xe6, + 0x71, 0x5b, 0xa8, 0xff, 0x00, 0x03, 0xd2, 0xbe, 0x73, 0x38, 0x86, 0x72, + 0xf6, 0xc1, 0xb7, 0x4f, 0x2a, 0xd1, 0x25, 0x0e, 0x01, 0x25, 0x27, 0xae, + 0x9d, 0x41, 0xed, 0xed, 0x52, 0xe8, 0xe0, 0x7b, 0xcf, 0xab, 0x0e, 0x5d, + 0x30, 0x96, 0xe7, 0xee, 0x4f, 0x31, 0x57, 0xc1, 0x00, 0x7e, 0x6a, 0xaf, + 0x15, 0x8b, 0x63, 0x17, 0x6e, 0x1a, 0x61, 0x24, 0x92, 0x65, 0x6b, 0x3b, + 0xa8, 0xf7, 0x3e, 0x9d, 0x87, 0x4a, 0x63, 0x45, 0x14, 0x51, 0x45, 0x14, + 0x51, 0x45, 0x7f, 0xff, 0xd9 +}; + +/* length of data in image_jpg */ +static const unsigned int image_jpg_len = sizeof(image_jpg); + +/* dimensions of image */ +static const unsigned int image_jpg_x = 64; +static const unsigned int image_jpg_y = 64; + +/* start of JPEG image data section */ +static const unsigned int image_data_offset = 20; +#define image_data_len (image_jpg_len - image_data_offset) + +/* raw EXIF header data */ +static const unsigned char exif_header[] = { + 0xff, 0xd8, 0xff, 0xe1 +}; +/* length of data in exif_header */ +static const unsigned int exif_header_len = sizeof(exif_header); + +/* byte order to use in the EXIF block */ +#define FILE_BYTE_ORDER EXIF_BYTE_ORDER_INTEL + +/* comment to write into the EXIF block */ +#define FILE_COMMENT "libexif demonstration image" + +/* special header required for EXIF_TAG_USER_COMMENT */ +#define ASCII_COMMENT "ASCII\0\0\0" + + +/* Get an existing tag, or create one if it doesn't exist */ +static ExifEntry *init_tag(ExifData *exif, ExifIfd ifd, ExifTag tag) +{ + ExifEntry *entry; + /* Return an existing tag if one exists */ + if (!((entry = exif_content_get_entry (exif->ifd[ifd], tag)))) { + /* Allocate a new entry */ + entry = exif_entry_new (); + assert(entry != NULL); /* catch an out of memory condition */ + entry->tag = tag; /* tag must be set before calling + exif_content_add_entry */ + + /* Attach the ExifEntry to an IFD */ + exif_content_add_entry (exif->ifd[ifd], entry); + + /* Allocate memory for the entry and fill with default data */ + exif_entry_initialize (entry, tag); + + /* Ownership of the ExifEntry has now been passed to the IFD. + * One must be very careful in accessing a structure after + * unref'ing it; in this case, we know "entry" won't be freed + * because the reference count was bumped when it was added to + * the IFD. + */ + exif_entry_unref(entry); + } + return entry; +} + +/* Create a brand-new tag with a data field of the given length, in the + * given IFD. This is needed when exif_entry_initialize() isn't able to create + * this type of tag itself, or the default data length it creates isn't the + * correct length. + */ +static ExifEntry *create_tag(ExifData *exif, ExifIfd ifd, ExifTag tag, size_t len) +{ + void *buf; + ExifEntry *entry; + + /* Create a memory allocator to manage this ExifEntry */ + ExifMem *mem = exif_mem_new_default(); + assert(mem != NULL); /* catch an out of memory condition */ + + /* Create a new ExifEntry using our allocator */ + entry = exif_entry_new_mem (mem); + assert(entry != NULL); + + /* Allocate memory to use for holding the tag data */ + buf = exif_mem_alloc(mem, len); + assert(buf != NULL); + + /* Fill in the entry */ + entry->data = buf; + entry->size = len; + entry->tag = tag; + entry->components = len; + entry->format = EXIF_FORMAT_UNDEFINED; + + /* Attach the ExifEntry to an IFD */ + exif_content_add_entry (exif->ifd[ifd], entry); + + /* The ExifMem and ExifEntry are now owned elsewhere */ + exif_mem_unref(mem); + exif_entry_unref(entry); + + return entry; +} + +int main(int argc, char **argv) +{ + int rc = 1; + FILE *f; + unsigned char *exif_data; + unsigned int exif_data_len; + ExifEntry *entry; + ExifData *exif = exif_data_new(); + if (!exif) { + fprintf(stderr, "Out of memory\n"); + return 2; + } + + /* Set the image options */ + exif_data_set_option(exif, EXIF_DATA_OPTION_FOLLOW_SPECIFICATION); + exif_data_set_data_type(exif, EXIF_DATA_TYPE_COMPRESSED); + exif_data_set_byte_order(exif, FILE_BYTE_ORDER); + + /* Create the mandatory EXIF fields with default data */ + exif_data_fix(exif); + + /* All these tags are created with default values by exif_data_fix() */ + /* Change the data to the correct values for this image. */ + entry = init_tag(exif, EXIF_IFD_EXIF, EXIF_TAG_PIXEL_X_DIMENSION); + exif_set_long(entry->data, FILE_BYTE_ORDER, image_jpg_x); + + entry = init_tag(exif, EXIF_IFD_EXIF, EXIF_TAG_PIXEL_Y_DIMENSION); + exif_set_long(entry->data, FILE_BYTE_ORDER, image_jpg_y); + + entry = init_tag(exif, EXIF_IFD_EXIF, EXIF_TAG_COLOR_SPACE); + exif_set_short(entry->data, FILE_BYTE_ORDER, 1); + + /* Create a EXIF_TAG_USER_COMMENT tag. This one must be handled + * differently because that tag isn't automatically created and + * allocated by exif_data_fix(), nor can it be created using + * exif_entry_initialize() so it must be explicitly allocated here. + */ + entry = create_tag(exif, EXIF_IFD_EXIF, EXIF_TAG_USER_COMMENT, + sizeof(ASCII_COMMENT) + sizeof(FILE_COMMENT) - 2); + /* Write the special header needed for a comment tag */ + memcpy(entry->data, ASCII_COMMENT, sizeof(ASCII_COMMENT)-1); + /* Write the actual comment text, without the trailing NUL character */ + memcpy(entry->data+8, FILE_COMMENT, sizeof(FILE_COMMENT)-1); + /* create_tag() happens to set the format and components correctly for + * EXIF_TAG_USER_COMMENT, so there is nothing more to do. */ + + /* Create a EXIF_TAG_SUBJECT_AREA tag */ + entry = create_tag(exif, EXIF_IFD_EXIF, EXIF_TAG_SUBJECT_AREA, + 4 * exif_format_get_size(EXIF_FORMAT_SHORT)); + entry->format = EXIF_FORMAT_SHORT; + entry->components = 4; + exif_set_short(entry->data, FILE_BYTE_ORDER, image_jpg_x / 2); + exif_set_short(entry->data+2, FILE_BYTE_ORDER, image_jpg_y / 2); + exif_set_short(entry->data+4, FILE_BYTE_ORDER, image_jpg_x); + exif_set_short(entry->data+6, FILE_BYTE_ORDER, image_jpg_y); + + /* Get a pointer to the EXIF data block we just created */ + exif_data_save_data(exif, &exif_data, &exif_data_len); + assert(exif_data != NULL); + + f = fopen(FILE_NAME, "wb"); + if (!f) { + fprintf(stderr, "Error creating file %s\n", FILE_NAME); + exif_data_unref(exif); + return rc; + } + /* Write EXIF header */ + if (fwrite(exif_header, exif_header_len, 1, f) != 1) { + fprintf(stderr, "Error writing to file %s\n", FILE_NAME); + goto errout; + } + /* Write EXIF block length in big-endian order */ + if (fputc((exif_data_len+2) >> 8, f) < 0) { + fprintf(stderr, "Error writing to file %s\n", FILE_NAME); + goto errout; + } + if (fputc((exif_data_len+2) & 0xff, f) < 0) { + fprintf(stderr, "Error writing to file %s\n", FILE_NAME); + goto errout; + } + /* Write EXIF data block */ + if (fwrite(exif_data, exif_data_len, 1, f) != 1) { + fprintf(stderr, "Error writing to file %s\n", FILE_NAME); + goto errout; + } + /* Write JPEG image data, skipping the non-EXIF header */ + if (fwrite(image_jpg+image_data_offset, image_data_len, 1, f) != 1) { + fprintf(stderr, "Error writing to file %s\n", FILE_NAME); + goto errout; + } + printf("Wrote file %s\n", FILE_NAME); + rc = 0; + +errout: + if (fclose(f)) { + fprintf(stderr, "Error writing to file %s\n", FILE_NAME); + rc = 1; + } + /* The allocator we're using for ExifData is the standard one, so use + * it directly to free this pointer. + */ + free(exif_data); + exif_data_unref(exif); + + return rc; +} |