/* * 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 <libexif/exif-data.h> /* 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); } } } /* 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); } } } } } } int main(int argc, char **argv) { ExifData *ed; ExifEntry *entry; 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; } /* Show all the tags that might contain information about the * photographer */ show_tag(ed, EXIF_IFD_0, EXIF_TAG_ARTIST); show_tag(ed, EXIF_IFD_0, EXIF_TAG_XP_AUTHOR); show_tag(ed, EXIF_IFD_0, EXIF_TAG_COPYRIGHT); /* These are much less likely to be useful */ show_tag(ed, EXIF_IFD_EXIF, EXIF_TAG_USER_COMMENT); show_tag(ed, EXIF_IFD_0, EXIF_TAG_IMAGE_DESCRIPTION); show_tag(ed, EXIF_IFD_1, EXIF_TAG_IMAGE_DESCRIPTION); /* A couple of MakerNote tags can contain useful data. Read the * manufacturer tag to see if this image could have one of the recognized * MakerNote tags. */ entry = exif_content_get_entry(ed->ifd[EXIF_IFD_0], EXIF_TAG_MAKE); if (entry) { char buf[64]; /* Get the contents of the manufacturer tag as a string */ if (exif_entry_get_value(entry, buf, sizeof(buf))) { trim_spaces(buf); if (!strcmp(buf, "Canon")) { show_mnote_tag(ed, 9); /* MNOTE_CANON_TAG_OWNER */ } else if (!strcmp(buf, "Asahi Optical Co.,Ltd.") || !strcmp(buf, "PENTAX Corporation")) { show_mnote_tag(ed, 0x23); /* MNOTE_PENTAX2_TAG_HOMETOWN_CITY */ } } } /* Free the EXIF data */ exif_data_unref(ed); return 0; }