On OS X, read Exif tags using Cocoa's built-in functionality

This allows for RAW files Exif reading. Fixes #234.

cocoa/inter/app_pe.py

@@ -6,7 +6,6 @@
 # which should be included with this package. The terms are also available at 
 # http://www.hardcoded.net/licenses/bsd_license
 
-import os.path as op
 import plistlib
 import logging
 import re
@@ -48,6 +47,16 @@ class Photo(PhotoBase):
             raise IOError('The picture %s could not be read' % str(self.path))
         return blocks
     
+    def _get_exif_timestamp(self):
+        exifdata = proxy.readExifData_(str(self.path))
+        if exifdata:
+            try:
+                return exifdata['{Exif}']['DateTimeOriginal']
+            except KeyError:
+                return ''
+        else:
+            return ''
+    
 
 class IPhoto(Photo):
     def __init__(self, path, db_id):

cocoalib/cocoa/CocoaProxy.h

@@ -30,4 +30,5 @@
 - (void)destroyPool;
 - (void)reportCrash:(NSString *)crashReport;
 - (void)log:(NSString *)s;
+- (NSDictionary *)readExifData:(NSString *)imagePath;
 @end

cocoalib/cocoa/CocoaProxy.m

@@ -157,4 +157,20 @@
 {
     NSLog(@"%@", s);
 }
+
+- (NSDictionary *)readExifData:(NSString *)imagePath
+{
+    NSDictionary *result = nil;
+    NSURL* url = [NSURL fileURLWithPath:imagePath];
+    CGImageSourceRef source = CGImageSourceCreateWithURL((CFURLRef)url, nil);
+    if (source != nil) {
+        CFDictionaryRef metadataRef = CGImageSourceCopyPropertiesAtIndex (source, 0, nil);
+        if (metadataRef != nil) {
+            result = [NSDictionary dictionaryWithDictionary:(NSDictionary *)metadataRef];
+            CFRelease(metadataRef);
+        }
+        CFRelease(source);
+    }
+    return result;
+}
 @end

core_pe/photo.py

@@ -49,6 +49,15 @@ class Photo(fs.File):
                 self._cached_orientation = 0
         return self._cached_orientation
     
+    def _get_exif_timestamp(self):
+        try:
+            with self.path.open('rb') as fp:
+                exifdata = exif.get_fields(fp)
+                return exifdata['DateTimeOriginal']
+        except Exception:
+            logging.info("Couldn't read EXIF of picture: %s", self.path)
+        return ''
+    
     @classmethod
     def can_handle(cls, path):
         return fs.File.can_handle(path) and get_file_ext(path[-1]) in cls.HANDLED_EXTS
@@ -89,12 +98,7 @@ class Photo(fs.File):
             if self._get_orientation() in {5, 6, 7, 8}:
                 self.dimensions = (self.dimensions[1], self.dimensions[0])
         elif field == 'exif_timestamp':
-            try:
-                with self.path.open('rb') as fp:
-                    exifdata = exif.get_fields(fp)
-                    self.exif_timestamp = exifdata['DateTimeOriginal']
-            except Exception:
-                logging.info("Couldn't read EXIF of picture: %s", self.path)
+            self.exif_timestamp = self._get_exif_timestamp()
     
     def get_blocks(self, block_count_per_side):
         return self._plat_get_blocks(block_count_per_side, self._get_orientation())