Potential leak of an object stored into 'imageCrop'

Question

This code running fine but when analyse, it shows potential memory leaks. It seems that imageCrop has potential memory leak. Your help is highly appreciated.

Here is my code.

-(CATransformLayer *)transformLayerFromImage:(UIImage *)image Frame:(CGRect)frame Duration:(CGFloat)duration AnchorPiont:(CGPoint)anchorPoint StartAngle:(double)start EndAngle:(double)end
{
    CATransformLayer *jointLayer = [CATransformLayer layer];
    jointLayer.anchorPoint = anchorPoint;
    CALayer *imageLayer = [CALayer layer];
    CAGradientLayer *shadowLayer = [CAGradientLayer layer];
    double shadowAniOpacity;

    if (anchorPoint.y == 0.5) {
        CGFloat layerWidth;
        if (anchorPoint.x == 0 ) //from left to right
        {
            layerWidth = image.size.width - frame.origin.x;
            jointLayer.frame = CGRectMake(0, 0, layerWidth, frame.size.height);
            if (frame.origin.x) {
                jointLayer.position = CGPointMake(frame.size.width, frame.size.height/2);
            }
            else {
                jointLayer.position = CGPointMake(0, frame.size.height/2);
            }
        }
        else { //from right to left
            layerWidth = frame.origin.x + frame.size.width;
            jointLayer.frame = CGRectMake(0, 0, layerWidth, frame.size.height);
            jointLayer.position = CGPointMake(layerWidth, frame.size.height/2);
        }

        //map image onto transform layer
        imageLayer.frame = CGRectMake(0, 0, frame.size.width, frame.size.height);
        imageLayer.anchorPoint = anchorPoint;
        imageLayer.position = CGPointMake(layerWidth*anchorPoint.x, frame.size.height/2);
        [jointLayer addSublayer:imageLayer];
        CGImageRef imageCrop = CGImageCreateWithImageInRect(image.CGImage, frame);
        imageLayer.contents = (__bridge id)imageCrop;
        imageLayer.backgroundColor = [UIColor clearColor].CGColor;

        //add shadow
        NSInteger index = frame.origin.x/frame.size.width;
        shadowLayer.frame = imageLayer.bounds;
        shadowLayer.backgroundColor = [UIColor darkGrayColor].CGColor;
        shadowLayer.opacity = 0.0;
        shadowLayer.colors = [NSArray arrayWithObjects:(id)[UIColor blackColor].CGColor, (id)[UIColor clearColor].CGColor, nil];
        if (index%2) {
            shadowLayer.startPoint = CGPointMake(0, 0.5);
            shadowLayer.endPoint = CGPointMake(1, 0.5);
            shadowAniOpacity = (anchorPoint.x)?0.24:0.32;
        }
        else {
            shadowLayer.startPoint = CGPointMake(1, 0.5);
            shadowLayer.endPoint = CGPointMake(0, 0.5);
            shadowAniOpacity = (anchorPoint.x)?0.32:0.24;
        }
    }
    else{
        CGFloat layerHeight;
        if (anchorPoint.y == 0 ) //from top
        {
            layerHeight = image.size.height - frame.origin.y;
            jointLayer.frame = CGRectMake(0, 0, frame.size.width, layerHeight);
            if (frame.origin.y) {
                jointLayer.position = CGPointMake(frame.size.width/2, frame.size.height);
            }
            else {
                jointLayer.position = CGPointMake(frame.size.width/2, 0);
            }
        }
        else { //from bottom
            layerHeight = frame.origin.y + frame.size.height;
            jointLayer.frame = CGRectMake(0, 0, frame.size.width, layerHeight);
            jointLayer.position = CGPointMake(frame.size.width/2, layerHeight);
        }

        //map image onto transform layer
        imageLayer.frame = CGRectMake(0, 0, frame.size.width, frame.size.height);
        imageLayer.anchorPoint = anchorPoint;
        imageLayer.position = CGPointMake(frame.size.width/2, layerHeight*anchorPoint.y);
        [jointLayer addSublayer:imageLayer];
        CGImageRef imageCrop = CGImageCreateWithImageInRect(image.CGImage, frame);
        imageLayer.contents = (__bridge id)imageCrop;
        imageLayer.backgroundColor = [UIColor clearColor].CGColor;

        //add shadow
        NSInteger index = frame.origin.y/frame.size.height;
        shadowLayer.frame = imageLayer.bounds;
        shadowLayer.backgroundColor = [UIColor darkGrayColor].CGColor;
        shadowLayer.opacity = 0.0;
        shadowLayer.colors = [NSArray arrayWithObjects:(id)[UIColor blackColor].CGColor, (id)[UIColor clearColor].CGColor, nil];
        if (index%2) {
            shadowLayer.startPoint = CGPointMake(0.5, 0);
            shadowLayer.endPoint = CGPointMake(0.5, 1);
            shadowAniOpacity = (anchorPoint.x)?0.24:0.32;
        }
        else {
            shadowLayer.startPoint = CGPointMake(0.5, 1);
            shadowLayer.endPoint = CGPointMake(0.5, 0);
            shadowAniOpacity = (anchorPoint.x)?0.32:0.24;
        }
    }

    [imageLayer addSublayer:shadowLayer];

    //animate open/close animation
    CABasicAnimation* animation = (anchorPoint.y == 0.5)?[CABasicAnimation animationWithKeyPath:@"transform.rotation.y"]:[CABasicAnimation animationWithKeyPath:@"transform.rotation.x"];
    [animation setDuration:duration];
    [animation setFromValue:[NSNumber numberWithDouble:start]];
    [animation setToValue:[NSNumber numberWithDouble:end]];
    [animation setRemovedOnCompletion:NO];
    [jointLayer addAnimation:animation forKey:@"jointAnimation"];

    //animate shadow opacity
    animation = [CABasicAnimation animationWithKeyPath:@"opacity"];
    [animation setDuration:duration];
    [animation setFromValue:[NSNumber numberWithDouble:(start)?shadowAniOpacity:0]];
    [animation setToValue:[NSNumber numberWithDouble:(start)?0:shadowAniOpacity]];
    [animation setRemovedOnCompletion:NO];
    [shadowLayer addAnimation:animation forKey:nil];

    return jointLayer;
}

Answer 1

Whatever you create with CGImageCreateWithImageInRect should be released as this is a function from unmanaged memory land.

1. Use CGImageRelease to release the reference to unmanaged object:

    CGImageRelease(imageCrop); imageCrop = NULL; 

OR

2. Use __bridge_transfer instead of __bridge to transfer object ownership over CGImageRef to ARC.

    imageLayer.contents = (__bridge_transfer id)imageCrop; 

   In that case ARC will efficiently do #1 for you.

Good reads:

1. There is a great post on bridging in Objective-C: https://stackoverflow.com/a/17256947/351305
2. And related question: Does ARC work with Core Graphics objects?