iPhone - UIImage Leak, CGBitmapContextCreateImage Leak

Question

Alright I am having a world of difficulty tracking down this memory leak. When running this script I do not see any memory leaking, but my objectalloc is climbing. Instruments points to CGBitmapContextCreateImage > create_bitmap_data_provider > malloc, this takes up 60% of my objectalloc.

This code is called several times with a NSTimer.

 //GET IMAGE FROM RESOURCE DIR
  NSString * fileLocation = [[NSBundle mainBundle] pathForResource:imgMain ofType:@"jpg"];
  NSData * imageData = [NSData dataWithContentsOfFile:fileLocation];
  UIImage * blurMe = [UIImage imageWithData:imageData];

  NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

    UIImage * scaledImage = [blurMe _imageScaledToSize:CGSizeMake(blurMe.size.width / dblBlurLevel, blurMe.size.width / dblBlurLevel) interpolationQuality:3.0];
    UIImage * labelImage = [scaledImage _imageScaledToSize:blurMe.size interpolationQuality:3.0];
    UIImage * imageCopy = [[UIImage alloc] initWithCGImage:labelImage.CGImage];

  [pool drain]; // deallocates scaledImage and labelImage

  imgView.image = imageCopy;
  [imageCopy release];

Below is the blur function. I believe the objectalloc issue is located in here. Maybe I just need a pair of fresh eyes. Would be great if someone could figure this out. Sorry it is kind of long... I'll try and shorten it.

    @implementation UIImage(Blur)
    - (UIImage *)blurredCopy:(int)pixelRadius
    {
        //VARS
        unsigned char *srcData, *destData, *finalData;
        CGContextRef    context = NULL;
        CGColorSpaceRef colorSpace;
        void *          bitmapData;
        int             bitmapByteCount;
        int             bitmapBytesPerRow;

        //IMAGE SIZE
        size_t pixelsWide = CGImageGetWidth(self.CGImage);
        size_t pixelsHigh = CGImageGetHeight(self.CGImage);
        bitmapBytesPerRow   = (pixelsWide * 4);
        bitmapByteCount     = (bitmapBytesPerRow * pixelsHigh);

        colorSpace = CGColorSpaceCreateDeviceRGB();
        if (colorSpace == NULL) { return NULL; }

        bitmapData = malloc( bitmapByteCount );
        if (bitmapData == NULL) { CGColorSpaceRelease( colorSpace ); }

        context = CGBitmapContextCreate (bitmapData,
                         pixelsWide,
                         pixelsHigh,
                         8,    
                         bitmapBytesPerRow,
                         colorSpace,
                         kCGImageAlphaPremultipliedFirst );
        if (context == NULL) { free (bitmapData); }

        CGColorSpaceRelease( colorSpace );
        free (bitmapData);

        if (context == NULL) { return NULL; }

        //PREPARE BLUR
        size_t width = CGBitmapContextGetWidth(context);
        size_t height = CGBitmapContextGetHeight(context);
        size_t bpr = CGBitmapContextGetBytesPerRow(context);
        size_t bpp = (CGBitmapContextGetBitsPerPixel(context) / 8);
        CGRect rect = {{0,0},{width,height}}; 

        CGContextDrawImage(context, rect, self.CGImage); 

        // Now we can get a pointer to the image data associated with the bitmap
        // context.
        srcData = (unsigned char *)CGBitmapContextGetData (context);
        if (srcData != NULL)
        {

            size_t dataSize = bpr * height;
            finalData = malloc(dataSize);
            destData = malloc(dataSize);
            memcpy(finalData, srcData, dataSize);
            memcpy(destData, srcData, dataSize);

            int sums[5];
            int i, x, y, k;
            int gauss_sum=0;
            int radius = pixelRadius * 2 + 1;
            int *gauss_fact = malloc(radius * sizeof(int));

            for (i = 0; i < pixelRadius; i++)
            {
            .....blah blah blah...
                THIS IS JUST LONG CODE THE CREATES INT FIGURES
                ........blah blah blah......
                }


            if (gauss_fact) { free(gauss_fact); }
        }

        size_t bitmapByteCount2 = bpr * height;
       //CREATE DATA PROVIDER
        CGDataProviderRef dataProvider = CGDataProviderCreateWithData(NULL, srcData, bitmapByteCount2, NULL);

       //CREATE IMAGE
        CGImageRef cgImage = CGImageCreate(
                               width, 
                               height, 
                               CGBitmapContextGetBitsPerComponent(context),
                               CGBitmapContextGetBitsPerPixel(context), 
                               CGBitmapContextGetBytesPerRow(context),
                               CGBitmapContextGetColorSpace(context), 
                               CGBitmapContextGetBitmapInfo(context), 
                               dataProvider, 
                               NULL, 
                               true, 
                               kCGRenderingIntentDefault
                                     );

       //RELEASE INFORMATION
        CGDataProviderRelease(dataProvider);
        CGContextRelease(context); 

        if (destData) { free(destData); }
        if (finalData) { free(finalData); }
        if (srcData) { free(srcData); }


        UIImage *retUIImage = [UIImage imageWithCGImage:cgImage];
        CGImageRelease(cgImage);

        return retUIImage;
  }

The only thing I can think of that is holding up the objectalloc is this UIImage *retUIImage = [UIImage imageWithCGImage:cgImage];...but how to do I release that after it has been returned? Hopefully someone can help please.

Answer 1

I have used Quartz many times. Every time I do is a nightmare. As far as I noticed, and I have filled a bug on Apple sending a project as proof of crash, one of 4 things is true:

1. Quartz leaks as hell
2. It takes too long to release the memory
3. it uses too much memory unnecessarily or
4. a combination of all them.

I once created a simple project to prove that. The project had a button. Every time the button was pressed a small image (100x100 pixels) was added to the screen. The image was composed by two layers, the image itself and an additional layer containing a dashed line drawn around the image border. This drawing was done in Quartz. Pressing 8 times the button made the application crash. You can say: pressing the button 8 times and 16 images were added to the screen, this is the reason for crashing, right?

Instead of drawing the border using Quartz, I decided to have the border pre-draw on a PNG and just add it as a layer to the object. The same two layers per object created. Right?

I clicked 100 times, adding 200 images to the screen and no crash. The memory never went above 800 Kb. I could continue clicking... the app continued snappier and fast. No memory warning, no crash.

Apple has to review Quartz urgently.