contrib/examples/photographer.c: Added example program to show how

to display EXIF and MakerNote tags

diff --git a/ChangeLog b/ChangeLog
index 7fc9f46..9b6ea10 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2009-01-03  Dan Fandrich <dan@coneharvesters.com>
+
+       * contrib/examples/photographer.c: Added example program to show how
+         to display EXIF and MakerNote tags
+
 2008-12-22  Dan Fandrich <dan@coneharvesters.com>
 
        * po/vi.po: Updated Vietnamese translation by Clytie Siddall

diff --git a/contrib/examples/Makefile.am b/contrib/examples/Makefile.am
index dac4e0c..c1eebd5 100644 (file)
--- a/contrib/examples/Makefile.am
+++ b/contrib/examples/Makefile.am
@@ -1,5 +1,5 @@
 # Simple example programs
-check_PROGRAMS = thumbnail
+check_PROGRAMS = photographer thumbnail
 
 # Example programs with dependencies other than plain libexif
 COMPLICATED_EXAMPLES = cam_features.c

diff --git a/contrib/examples/photographer.c b/contrib/examples/photographer.c
new file mode 100644 (file)
index 0000000..f0b586b
--- /dev/null
+++ b/contrib/examples/photographer.c
@@ -0,0 +1,127 @@
+/*
+ * 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;
+
+    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.
+     */
+    ExifEntry *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")) {
+                /* MNOTE_CANON_TAG_OWNER */
+                show_mnote_tag(ed, 9);
+
+            } else if (!strcmp(buf, "Asahi Optical Co.,Ltd.") || 
+                       !strcmp(buf, "PENTAX Corporation")) {
+                /* MNOTE_PENTAX2_TAG_HOMETOWN_CITY */
+                show_mnote_tag(ed, 0x23);
+            }
+        }
+    }
+
+    /* Free the EXIF data */
+    exif_data_unref(ed);
+
+    return 0;
+}