read-exif-new

/*
 * libexif example program to display the contents of a number of specific
 * EXIF and MakerNote tags. The tags selected are those that may aid in
 * identification of the photographer who took the image.
 *
 * Placed into the public domain by Dan Fandrich
 */

#include <stdio.h>
#include <string.h>
#include <assert.h>
#include <libexif/exif-data.h>

#define FILE_BYTE_ORDER EXIF_BYTE_ORDER_INTEL

/* Remove spaces on the right of the string */
static void trim_spaces(char *buf)
{
    char *s = buf-1;
    for (; *buf; ++buf) {
        if (*buf != ' ')
            s = buf;
    }
    *++s = 0; /* nul terminate the string on the first of the final spaces */
}

/* Show the tag name and contents if the tag exists */
static void show_tag(ExifData *d, ExifIfd ifd, ExifTag tag)
{
    /* See if this tag exists */
    ExifEntry *entry = exif_content_get_entry(d->ifd[ifd],tag);
    if (entry) {
        char buf[1024];

        /* Get the contents of the tag in human-readable form */
        exif_entry_get_value(entry, buf, sizeof(buf));

        /* Don't bother printing it if it's entirely blank */
        trim_spaces(buf);
        if (*buf) {
            printf("%s: %s\n", exif_tag_get_name_in_ifd(tag,ifd), buf);
        }
    }
}

static char* read_tag(ExifData *ed, ExifIfd eid, ExifTag tag){
    static char result[1024];
    ExifEntry *entry = exif_content_get_entry(ed->ifd[eid], tag);

    if (entry){
        char buf[1024];

        exif_entry_get_value(entry, buf, sizeof(buf));
        trim_spaces(buf);

        if (*buf) strcpy(result, buf);
        else strcpy(result, "NULL");
    }
    else strcpy(result, "NULL");

    return result;
}

/* Show the given MakerNote tag if it exists */
static void show_mnote_tag(ExifData *d, unsigned tag)
{
    ExifMnoteData *mn = exif_data_get_mnote_data(d);
    if (mn) {
        int num = exif_mnote_data_count(mn);
        int i;

        /* Loop through all MakerNote tags, searching for the desired one */
        for (i=0; i < num; ++i) {
            char buf[1024];
            if (exif_mnote_data_get_id(mn, i) == tag) {
                if (exif_mnote_data_get_value(mn, i, buf, sizeof(buf))) {
                    /* Don't bother printing it if it's entirely blank */
                    trim_spaces(buf);
                    if (*buf) {
                        printf("%s: %s\n", exif_mnote_data_get_title(mn, i),
                            buf);
                    }
                }
            }
        }
    }
}

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;
}


int main(int argc, char **argv)
{
    ExifData *ed;
    ExifEntry *entry;
    unsigned char *data;
    unsigned int data_size;

    if (argc < 2) {
        printf("Usage: %s image.jpg\n", argv[0]);
        printf("Displays tags potentially relating to ownership "
                "of the image.\n");
        return 1;
    }

    /* Load an ExifData object from an EXIF file */
    ed = exif_data_new_from_file(argv[1]);
    if (!ed) {
        printf("File not readable or no EXIF data in file %s\n", argv[1]);
        return 2;
    }

    printf("Model : %s\n", read_tag(ed, EXIF_IFD_0, EXIF_TAG_MODEL));
    printf("Software: %s\n", read_tag(ed, EXIF_IFD_0, EXIF_TAG_SOFTWARE));

    entry = init_tag(ed, EXIF_IFD_EXIF, EXIF_TAG_MODEL);
    exif_set_long(entry->data, FILE_BYTE_ORDER, atol("Nokia 3330"));
    exif_data_save_data(ed, &data, &data_size);
    /* Free the EXIF data */
    exif_data_unref(ed);

    return 0;
}