Adding a subtle crossfade when transitioning NYTScalingImageView between placeholder and image.

CHANGELOG.md

@@ -6,6 +6,7 @@ Changes for users of the library currently on `develop`:
     - A data source no longer has to handle out-of-bounds indexes ([#227](https://github.com/NYTimes/NYTPhotoViewer/pull/227))
     - The data source is not retained ([#227](https://github.com/NYTimes/NYTPhotoViewer/pull/227))
 - Respect safe areas for iOS 11 support
+- Adding a subtle crossfade when transitioning `NYTScalingImageView` between placeholder and image.
 
 ## [1.2.0](https://github.com/NYTimes/NYTPhotoViewer/releases/tag/1.2.0)
 

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];