NSURL *imageRefURL = [info valueForKey:UIImagePickerControllerReferenceURL];

ALAssetsLibrary* assetLibrary = [[ALAssetsLibrary alloc] init];
void (^ALAssetsLibraryAssetForURLResultBlock)(ALAsset *) = ^(ALAsset *asset) {

if (asset != nil) {

ALAssetRepresentation *rep = [asset defaultRepresentation];
Byte imageBuffer = (Byte)malloc(rep.size);
NSUInteger bufferSize = [rep getBytes:imageBuffer fromOffset:0.0 length:rep.size error:nil];
NSData *imageData = [NSData dataWithBytesNoCopy:imageBuffer length:bufferSize freeWhenDone:YES];

// 这个imageData就是gif的了
} else {}
};

[assetLibrary assetForURL:imageRefURL
resultBlock:ALAssetsLibraryAssetForURLResultBlock
failureBlock:^(NSError *error){
}];