Deallocating images created with UIGraphicsBeginImageContext - iphone

Question

I'm creating images array for UIImageView so I can use [_myImageView startAnimating]; method. I figuree out that if I cache(preload) it like this way the animation is fluent.
But in Instruments I see, that game is deallocated but there is still too much memory allocated - I think there are some fragments of this UIGraphicsBeginContext stuff.
Am I using it right, is there some other way how to dealloc it?
Thanks in advance!
- (NSMutableArray *)generateCachedImageArrayWithFilename:(NSString *)filename extension:(NSString *)extension andImageCount:(int)count
{
_imagesArray = [[NSMutableArray alloc] init];
_fileExtension = extension;
_animationImageName = filename;
_imageCount = count;
for (int i = 0; i < count; i++)
{
NSString *tempImageNames = [NSString stringWithFormat:#"%#%i", filename, i];
NSString *imagePath = [[NSBundle mainBundle] pathForResource:tempImageNames ofType:extension];
UIImage *frameImage = [self loadRetinaImageIfAvailable:imagePath];
UIGraphicsBeginImageContext(frameImage.size);
CGRect rect = CGRectMake(0, 0, frameImage.size.width, frameImage.size.height);
[frameImage drawInRect:rect];
UIImage *renderedImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
[_imagesArray addObject:renderedImage];
if (_isDoublingFrames)
{
[_imagesArray addObject:renderedImage];
}
else if (_isTriplingFrames)
{
[_imagesArray addObject:renderedImage];
[_imagesArray addObject:renderedImage];
}
NSLog(#"filename = %#", filename);
}
return _imagesArray;
}
- (UIImage *)loadRetinaImageIfAvailable:(NSString *)path
{
NSString *retinaPath = [[path stringByDeletingLastPathComponent] stringByAppendingPathComponent:[NSString stringWithFormat:#"%##2x.%#", [[path lastPathComponent] stringByDeletingPathExtension], [path pathExtension]]];
if ([UIScreen mainScreen].scale == 2.0 && [[NSFileManager defaultManager] fileExistsAtPath:retinaPath] == YES)
return [[UIImage alloc] initWithCGImage:[[UIImage imageWithData:[NSData dataWithContentsOfFile:retinaPath]] CGImage] scale:2.0 orientation:UIImageOrientationUp];
else
return [UIImage imageWithContentsOfFile:path];
}
-(void) dealloc
{
[_imagesArray removeAllObjects];
_imagesArray = nil;
}

Answer 1

I had memory issues similar you wrote and what I would try out in your code
1) use #autoreleasepool
to wrap either the method or the content of the loop in #autoreleasepool { } to create a local pool which will be released after method is done. In your situation it seems to me wrapping the loop is better:
for (int i = 0; i < count; i++)
{
#autoreleasepool {
// the loop code
...
}}
2) kill [UIImage imageNamed]
Using imageNamed will prepare a cache (depending on the size of image) which will never be flushed out of the memory unless you reach a memory warning. Even if you set myImage.image = nil, the image is still in memory. XCode's Intruments tool Allocations view will show it nicely. What you can do is initialize UIImage like this, and iOS won't cache the image:
image = [UIImage imageWithContentsOfFile:fullpath];
You might use imageNamed in your code under loadRetinaImageIfAvailable.
Keep both two approach and let's check this out again!