UIImageView won't animate with UIImages of CGImage - objective-c

Question

I have a UIImageView that I am trying to make do an animation of a set of UIImages that are created by flipping other UIImages. Here's my code:
turtle = [[UIImageView alloc] initWithFrame:CGRectMake(self.view.frame.size.width-200,
self.view.frame.size.height - sand.frame.size.height - turtle.frame.size.height - 10 - heightOfKeyboard,
100,100)];
[flippedTurtleArray addObject:[UIImage imageWithCGImage:[UIImage imageNamed:#"Turtle1.png"].CGImage scale:1 orientation:UIImageOrientationDownMirrored]];
[flippedTurtleArray addObject:[UIImage imageWithCGImage:[UIImage imageNamed:#"Turtle2.png"].CGImage scale:1 orientation:UIImageOrientationDownMirrored]];
[flippedTurtleArray addObject:[UIImage imageWithCGImage:[UIImage imageNamed:#"Turtle3.png"].CGImage scale:1 orientation:UIImageOrientationDownMirrored]];
[flippedTurtleArray addObject:[UIImage imageWithCGImage:[UIImage imageNamed:#"Turtle2.png"].CGImage scale:1 orientation:UIImageOrientationDownMirrored]];
[self.view addSubview: turtle];
Problem is, when I try and make it animate from the array of flipped images, it shows the originals, not the flipped ones (i.e., when I do this):
turtle.animationImages = flippedTurtleArray;
turtle.animationDuration = 0.8f;
turtle.animationRepeatCount = 0;
[turtle startAnimating];
the original non flipped images are shown.
Now, if I do this however:
turtle.image = [flippedTurtleArray objectAtIndex:1];
the flipped image is shown. I thought maybe you can't do the animation with CGImage, but couldn't find that anyone else had had the same problem. Any ideas?
Thanks,
Sam

Answer 1

I would look at the CGLayer property, and specifically the transform property of the layer.
The Transform property is animatable, and would allow you to apply an arbitrary transform to you original image without having to manage your intermediate flipped Turtle Array.
The transform applied to the layer’s contents. Animatable.
#property CATransform3D transform
Discussion
This property is set to the identity transform by default. Any transformations you apply to the layer occur relative to the layer’s anchor point.
Availability
Available in iOS 2.0 and later.
Related Sample Code
oalTouch
Declared In
CALayer.h
If you have other reasons for wanting the array, then you may want to render the flipped image into a separate image, and pass that into your array.
Similarly if you can use iOS 7 as a target, take a look a SpriteKit, it may make the whole task much simpler.