Adding a subtle crossfade when transitioning NYTScalingImageView be…

…tween placeholder and image.

I noticed especially with differing aspect ratios that this was a fairly jarring transition.

NYTPhotoViewer/NYTScalingImageView.m

@@ -118,8 +118,11 @@ - (void)updateImage:(UIImage *)image imageData:(NSData *)imageData {
 
     // Remove any transform currently applied by the scroll view zooming.
     self.imageView.transform = CGAffineTransformIdentity;
-    self.imageView.image = imageToUse;
-
+
+    [UIView transitionWithView:self.imageView duration:0.15f options:UIViewAnimationOptionTransitionCrossDissolve animations:^{
+        self.imageView.image = imageToUse;
+    } completion:nil];
+
 #ifdef ANIMATED_GIF_SUPPORT
     // It's necessarry to first assign the UIImage so calulations for layout go right (see above)
     self.imageView.animatedImage = [[FLAnimatedImage alloc] initWithAnimatedGIFData:imageData];