iPhone - CGBitmapContextCreateImage Leak, Anyone else with this problem?

Question

Has anyone else come across this problem? I am resizing images pretty often with an NSTimer. After using Instruments it does not show any memory leaks but my objectalloc just continues to climb. It points directly to CGBitmapContextCreateImage.

Anyone know of a solution? or Even possible ideas?

-(UIImage *) resizedImage:(UIImage *)inImage : (CGRect)thumbRect : (double)interpolationQuality
{
    CGImageRef   imageRef = [inImage CGImage];
    CGImageAlphaInfo alphaInfo = CGImageGetAlphaInfo(imageRef);

    if (alphaInfo == kCGImageAlphaNone)
     alphaInfo = kCGImageAlphaNoneSkipLast;

    // Build a bitmap context that's the size of the thumbRect
    CGContextRef bitmap = CGBitmapContextCreate(
        NULL,
        thumbRect.size.width,
        thumbRect.size.height,  
        CGImageGetBitsPerComponent(imageRef),
        4 * thumbRect.size.width, 
        CGImageGetColorSpace(imageRef),
        alphaInfo
        );

    // Draw into the context, this scales the image
    CGContextSetInterpolationQuality(bitmap, interpolationQuality);
    CGContextDrawImage(bitmap, thumbRect, imageRef);

    // Get an image from the context and a UIImage
    CGImageRef ref = CGBitmapContextCreateImage(bitmap);
    UIImage* result = [UIImage imageWithCGImage:ref];

    CGContextRelease(bitmap); // ok if NULL
    CGImageRelease(ref);

    return [result autorelease];
}

Answer 1

Just a sanity check: are you releasing the return UIImage -- normally i would expect a function that allocating a new object (in this case a UIImage) to have create in the name?

Perhaps you want

return [result autorelease]

?

Answer 2

Why not use the simpler UIGraphicsBeginImageContext?

@implementation UIImage(ResizeExtension)
- (UIImage *)resizedImageWithSize:(CGSize)newSize interpolationQuality:(CGInterpolationQuality)interpolationQuality;
@end
@implementation UIImage(ResizeExtension)
- (UIImage *)resizedImageWithSize:(CGSize)newSize interpolationQuality:(CGInterpolationQuality)interpolationQuality
{
 UIGraphicsBeginImageContext(newSize);
 CGContextRef context = UIGraphicsGetCurrentContext();
 CGContextSetInterpolationQuality(context, interpolationQuality);
 [image drawInRect:CGRectMake(0, 0, newSize.width, newSize.height)];
 UIImage *result = UIGraphicsGetImageFromCurrentImageContext();
 UIGraphicsEndImageContext();
 return result;
}

@end

_{Also, this will return an image retained by the current autorelease pool; if you are creating many of these images in a loop, allocate and drain an NSAutoreleasePool manually.}