How to release CGImageRef if required to return it?

Question

I have a method to resize a CGImageRef and return CGImageRef. The issue is the last few lines, where I need to somehow release but return it after. Any ideas? Thanks

 -(CGImageRef)resizeImage:(CGImageRef *)anImage width:(CGFloat)width height:(CGFloat)height
{

    CGImageRef imageRef = *anImage;

    CGImageAlphaInfo alphaInfo = CGImageGetAlphaInfo(imageRef);

    if (alphaInfo == kCGImageAlphaNone)
        alphaInfo = kCGImageAlphaNoneSkipLast;


    CGContextRef bitmap = CGBitmapContextCreate(NULL, width, height, CGImageGetBitsPerComponent(imageRef), 4 * width, CGImageGetColorSpace(imageRef), alphaInfo);

    CGContextDrawImage(bitmap, CGRectMake(0, 0, width, height), imageRef);

    CGImageRef ref = CGBitmapContextCreateImage(bitmap);

    CGContextRelease(bitmap);
    CGImageRelease(ref); //issue here

    return ref;

}

Answer 1

The Cocoa memory management naming policy states, that you own an object that is created from methods whose name begin with alloc, copy or new.
This rules are also respected by the Clang Static Analyzer.

Note that there are slightly different conventions for Core Foundation. Details can be found in Apple's Advanced Memory Management Programming Guide.

I modified your above method to conform to that naming conventions. I also removed the asterisk when passing in anImage, as CGImageRef is already a pointer. (Or was this on purpose?).
Note that you own the returned CGImage and have to CGImageRelease it later.

-(CGImageRef)newResizedImageWithImage:(CGImageRef)anImage width:(CGFloat)width height:(CGFloat)height
{
    CGImageAlphaInfo alphaInfo = CGImageGetAlphaInfo(anImage);
    if (alphaInfo == kCGImageAlphaNone)
    {
        alphaInfo = kCGImageAlphaNoneSkipLast;
    }
    CGContextRef bitmap = CGBitmapContextCreate(NULL, width, height, CGImageGetBitsPerComponent(anImage), 4 * width, CGImageGetColorSpace(anImage), alphaInfo);
    CGContextDrawImage(bitmap, CGRectMake(0, 0, width, height), anImage);
    CGImageRef image = CGBitmapContextCreateImage(bitmap);
    CGContextRelease(bitmap);
    return image;
}