UIImage+animatedGIF.h 1.73 KB
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#import <UIKit/UIKit.h>

/**
UIImage (animatedGIF)

This category adds class methods to `UIImage` to create an animated `UIImage` from an animated GIF.
*/
@interface UIImage (animatedGIF)

/*
UIImage *animation = [UIImage animatedImageWithAnimatedGIFData:theData];

I interpret `theData` as a GIF. I create an animated `UIImage` using the source images in the GIF.

The GIF stores a separate duration for each frame, in units of centiseconds (hundredths of a second). However, a `UIImage` only has a single, total `duration` property, which is a floating-point number.

To handle this mismatch, I add each source image (from the GIF) to `animation` a varying number of times to match the ratios between the frame durations in the GIF.

For example, suppose the GIF contains three frames. Frame 0 has duration 3. Frame 1 has duration 9. Frame 2 has duration 15. I divide each duration by the greatest common denominator of all the durations, which is 3, and add each frame the resulting number of times. Thus `animation` will contain frame 0 3/3 = 1 time, then frame 1 9/3 = 3 times, then frame 2 15/3 = 5 times. I set `animation.duration` to (3+9+15)/100 = 0.27 seconds.
*/
+ (UIImage *)animatedImageWithAnimatedGIFData:(NSData *)theData;

/*
UIImage *image = [UIImage animatedImageWithAnimatedGIFURL:theURL];

I interpret the contents of `theURL` as a GIF. I create an animated `UIImage` using the source images in the GIF.

I operate exactly like `+[UIImage animatedImageWithAnimatedGIFData:]`, except that I read the data from `theURL`. If `theURL` is not a `file:` URL, you probably want to call me on a background thread or GCD queue to avoid blocking the main thread.
*/
+ (UIImage *)animatedImageWithAnimatedGIFURL:(NSURL *)theURL;

@end