CGImageRef Memory leak

Question

I'm having a memory leak when using this custom method which returns a CGImageRef. I can't release "cgImage" properly because I have to return it. What chould I do ?

- (CGImageRef)rectRoundedImageRef:(CGRect)rect radius:(int)radius
{
    CGSize contextSize = CGSizeMake(rect.size.width, rect.size.height);     
    CGFloat imageScale = (CGFloat)1.0;
    CGFloat width = contextSize.width;
    CGFloat height = contextSize.height;        
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef context = CGBitmapContextCreate(NULL, width * imageScale, height * imageScale, 8, 0, colorSpace, kCGImageAlphaPremultipliedLast);
    // Draw ...
    // Get your image
    CGImageRef cgImage = CGBitmapContextCreateImage(context);       
    CGColorSpaceRelease(colorSpace);
    CGContextRelease(context);
    //CGImageRelease(cgImage); //If I release cgImage the app crashes.
    return cgImage;     
}

I had a similar leak. Try my answer here: http://stackoverflow.com/a/23669476/3631310 — Vlad, May 15 '14 at 06:46

Jacob Relkin · Accepted Answer · 2010-12-31T01:35:05.100

16

cgImage is owned by your method, you need to return it and give responsibility to the caller to release it through CFRelease.

You can also return the CGImage wrapped inside a UIImage instance, like this:

UIImage *image = [UIImage imageWithCGImage:cgImage];
CFRelease(cgImage); //cgImage is retained by the UIImage above
return image;

edited Dec 31 '10 at 01:35

answered Dec 31 '10 at 01:24

Jacob Relkin

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This answer is not relevant anymore: 'CFRelease' is unavailable: Core Foundation objects are automatically memory managed – Mycroft Canner Aug 23 '21 at 09:39

score 11 · Answer 2 · answered Dec 31 '10 at 01:25

This is a general problem with Core Foundation objects because there is no autorelease pool in CF. As I see it, you have two options to solve the problem:

Rename the method to something like -newRectRoundedImageRef:radius: to tell the caller that he takes ownership of the returned object and responsible for releasing it.
Wrap the CGImageRef in an autoreleased UIImage object and return that ([UIImage imageWithCGImage:]). That's probably what I would do.

score 3 · Answer 3 · answered Sep 10 '13 at 13:45

3

As suggested, we used:

CGImageRelease(imageRef);

but we still got an memory leak. our solution was to wrap code with an

@autoreleasepool {}

block and that solve our problem.

answered Sep 10 '13 at 13:45

shem

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Still doesnt release it properly tbh – Reza.Ab Nov 23 '17 at 16:32

score 3 · Answer 4 · answered Dec 31 '10 at 01:42

You can autorelease a Core Foundation-compatible object. it just looks a bit wonky. :)

The GC-safe way is like so:

CGImageRef image = ...;
if (image) {
    image = (CGImageRef)[[(id)image retain] autorelease];
    CGImageRelease(image);
}

The shortcut, which is safe on iOS but no longer safe on the Mac, is this:

CGImageRef image = ...;
if (image) {
    image = (CGImageRef)[(id)image autorelease];
}

Either one will place the image in an autorelease pool and prevent a leak.

CGImageRef Memory leak

4 Answers4

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