Merge branch 'date'

exiv2.js

@@ -2,3 +2,43 @@ var exiv2 = require('./build/Release/exiv2.node')
 
 // Export the properties implemented in the extension.
 exports = module.exports = exiv2;
+
+/**
+ * Convert exiv2's date-time strings into Date instances.
+ *
+ * The first parameter is the hash of tags loaded by getImageTags().
+ *
+ * The second parameter is an optional tag name. The default is
+ * 'Exif.Photo.DateTimeOriginal' with sub-second data being loaded from
+ * 'Exif.Photo.SubSecTimeOriginal', if it exists. See http://exiv2.org/tags.html
+ * for a complete list of tags.
+ */
+exports.getDate = function getDate(tags, dateTimeTag) {
+  dateTimeTag = dateTimeTag || 'Exif.Photo.DateTimeOriginal';
+  if (tags[dateTimeTag] === undefined) {
+    return null;
+  }
+
+  // Date.parse() doesn't recognize the custom format ('2012:04:14 17:45:52') so
+  // the easiest thing to do is convert it to ISO 8601 (e.g.
+  // "2012-04-14T17:45:52") which it does recognize. The colons in the date need
+  // to become hyphens and the space needs to become a 'T'.
+
+  // So split it into two...
+  var datetime = tags[dateTimeTag].split(' ');
+  // ...then change the colons in date into hyphens...
+  datetime[0] = datetime[0].replace(/:/g, '-');
+  // ...then join it back together with a 'T' and parse it.
+  var d = new Date(Date.parse(datetime.join('T')));
+
+  // If there's a matching sub second tag scale it from hundredths of a second
+  // to thousands and apply it to the date. The extra precision can be useful
+  // when sorting photos by time because multiple photos could be taken in a
+  // single second.
+  var subSecTag = dateTimeTag.replace(/\.DateTime/, '.SubSecTime');
+  if (tags[subSecTag] !== undefined) {
+    d.setMilliseconds(tags[subSecTag] * 10);
+  }
+
+  return d;
+}

test/test.js

@@ -1,5 +1,6 @@
 var exiv = require('../exiv2')
   , fs = require('fs')
+  , util = require('util')
   , should = require('should')
   , dir = __dirname + '/images';
 
@@ -139,4 +140,36 @@ describe('exiv2', function(){
       });
     });
   });
+
+  describe('.getDate()', function() {
+    var tags = {'Exif.Photo.DateTimeOriginal': '2012:04:14 17:45:52'};
+
+    it("should return a false value if the tag doesn't exist", function() {
+      var d = exiv.getDate({});
+      should.not.exist(d);
+    });
+
+    it("should return a Date", function() {
+      var d = exiv.getDate(tags);
+      should.ok(util.isDate(d));
+    });
+
+    it("should be the correct date and time", function() {
+      var d = exiv.getDate(tags);
+      d.toISOString().should.equal('2012-04-14T17:45:52.000Z');
+    });
+
+    it("should include milliseconds if available", function() {
+      tags['Exif.Photo.SubSecTimeOriginal'] = '99';
+      var d = exiv.getDate(tags);
+      d.toISOString().should.equal('2012-04-14T17:45:52.990Z');
+    });
+
+    it("should use custom tags", function() {
+      tags['Exif.Photo.DateTimeDigitized'] = '2012:04:14 17:08:08';
+      tags['Exif.Photo.SubSecTimeDigitized'] = '88';
+      var d = exiv.getDate(tags, 'Exif.Photo.DateTimeDigitized');
+      d.toISOString().should.equal('2012-04-14T17:08:08.880Z');
+    });
+  })
 })