UIImage Sprite Additions

Useful UIImage category for handling sprite sheets. This add-on smoothes the way of extracting images from a sprite sheet (texture atlas).

This can be useful in UIImageView animations where animationImages array has to be filled with a set of images representing frames. UIImage-Sprite category makes this process trivial by introducing two methods:

- (NSArray *)spritesWithSpriteSheetImage:(UIImage *)image spriteSize:(CGSize)size;
- (NSArray *)spritesWithSpriteSheetImage:(UIImage *)image inRange:(NSRange)range spriteSize:(CGSize)size;

Quick start

Just copy UIImage+Sprite.h and UIImage+Sprite.m to your project or use CocoaPods to install the pod.

Instructions for CocoaPods users:

1. Install CocoaPods with gem install cocoapods.

2. Create a file in your XCode project called Podfile and add the following line:

    pod 'UIImage+SpriteAdditions'
   

3. Run pod install in your xcode project directory. CocoaPods should download and install the UIImage+SpriteAdditions category, and create a new Xcode workspace. Open up this workspace in Xcode.

How to

There are two methods in UIImage+SpriteAdditions category. First one:

- (NSArray *)spritesWithSpriteSheetImage:(UIImage *)image  spriteSize:(CGSize)size;

The method returns an array with UIImage objects. Original sprite sheet (image) is sliced into smaller chunks, each of the specified size.

Second method is very similar:

- (NSArray *)spritesWithSpriteSheetImage:(UIImage *)image inRange:(NSRange)range spriteSize:(CGSize)size;

This method does exactly the same thing as the latter. However, this time we can specify the range of the chunks we want to get.

Note that for performance reasons you should not fire these methods every time you want to get the array of animation frames. You should rather fire it once and store the output array somewhere. This is because the CoreGraphics image manipulation operations (especially on large images) are not so fast and your application may slow down.

I wrote this add-on to facilitate the setup of short animations using UIImageView. For more complex animations I recommend using OpenGLES.

Demo

SpriteAnimationDemo project presents the usage of the UIImage+Sprite methods. The example shows how to create an animated UIImageView. This cool explosion sprite sheet which I included in the demo can be found here. I added some numbers to this image to make testing and debugging easier.

License

This code is distributed under the terms and conditions of the MIT license.

Copyright (c) 2011 Rafal Sroka