Cache Processed (e.g. blurred or edited) Images - ios

Question

Is there a best practice or library that helps cache processed images (i.e. images that have been created while the app is running) in iOS? I use SDWebImage for images that I download, but in various places in the app I blur or in other ways process some of these images. I would like to store the processed images in a cache so that I can access them easily rather than reprocess each time a user opens that image. What's the best way to do this?
Thanks!

Answer 1

The answer it seems is using NSCache. It's quite straightforward to do. I ended up with a subclass of NSCache to make sure memory warnings are handled.
Implementation of NATAutoPurgeCache (heavily based on other posts on StackOverflow)
#implementation NATAutoPurgeCache
+ (NATAutoPurgeCache *)sharedCache
{
static NATAutoPurgeCache *_sharedCache = nil;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
_sharedCache = [[self alloc] init];
});
return _sharedCache;
}
- (id)init
{
self = [super init];
if (self) {
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(removeAllObjects) name:UIApplicationDidReceiveMemoryWarningNotification object:nil];
}
return self;
}
- (void)dealloc
{
[[NSNotificationCenter defaultCenter] removeObserver:self name:UIApplicationDidReceiveMemoryWarningNotification object:nil];
}
#end
And using it when needed for an image: (in this case to store a blurred image)
UIImage* blurImage = [myCache objectForKey:#"blurred placeholder image"];
if (!blurImage)
{
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{
UIImage* blurImage = self.activityPic.image;
blurImage= [blurImage applyLightEffect];
dispatch_async(dispatch_get_main_queue(), ^{
self.activityPic.image = blurImage;
});
[myCache setObject:blurImage forKey:#"blurred placeholder image"];
});
}
else {
self.activityPic.image = blurImage;
}