Memory Leak when create a UIImage - ios

Question

I have following method to take a pdf file in documents directory and create a thumbnail out of it. This method is leaking memory in two places as shown in comments. Since I am using ARC I am not sure why is it leaking memory. How can I solve this.
+ (UIImage*)createPdfThumbnail:(NSString*)pdfFilePath {
NSURL *targetURL = [NSURL fileURLWithPath:pdfFilePath];
CGPDFDocumentRef pdf = CGPDFDocumentCreateWithURL((__bridge CFURLRef)targetURL); // 3.0% of memory leak
CGPDFPageRef page = CGPDFDocumentGetPage(pdf, 1);//for the first page
CGRect aRect = CGPDFPageGetBoxRect(page, kCGPDFCropBox);
UIGraphicsBeginImageContext(aRect.size);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSaveGState(context);
CGContextTranslateCTM(context, 0.0, aRect.size.height);
CGContextScaleCTM(context, 1.0, -1.0);
CGContextTranslateCTM(context, -(aRect.origin.x), -(aRect.origin.y));
CGContextSetGrayFillColor(context, 1.0, 1.0);
CGContextFillRect(context, aRect);
CGAffineTransform pdfTransform = CGPDFPageGetDrawingTransform(page, kCGPDFCropBox, aRect, 0, false);
CGContextConcatCTM(context, pdfTransform);
CGContextDrawPDFPage(context, page);
UIImage *thumbnail = UIGraphicsGetImageFromCurrentImageContext(); // 97% of memory leak
CGContextRestoreGState(context);
UIGraphicsEndImageContext();
CGPDFDocumentRelease(pdf);
return thumbnail;
}
EDIT:
-(void)fromJSON:(NSDictionary *)JSON{
[super fromJSON:JSON];
self.path = JSON[#"path"];
//Create and save thumbnail
if (self.parentSpecSheet != nil){
#autoreleasepool {
UIImage* thumbnail = [Utilities createPdfThumbnail:self.path];
Photo* thumbnailPhoto = [Photo addObject];
[thumbnailPhoto setDelta:#(0)];
[thumbnailPhoto setImage:thumbnail];
[thumbnailPhoto.file setDelta:#(0)];
self.parentSpecSheet.thumbnail = thumbnailPhoto;
}
}
}

Answer 1

Two thoughts:
I experience a significant leak from CGContextDrawPDFPage when I test your code in iOS5 (and if you search for "CGContextDrawPDFPage leak", you'll see tons of references to permutations of this problem). This appears to be a known problem.
I see no appreciable leak in iOS 6 from the above code, though.
If you're still seeing this leak in iOS 6, then I suspect the problem does not rest in the above code. Do you have any other leaks reported? I'd also suggest you confirm that the object that owns this thumbnail is successfully getting deallocated itself (e.g. log/breakpoint in its dealloc method).
Unfortunately, when you look at the leaks tool, it's reporting where the leaked object was instantiated, not where the leak took place. You might want to confirm that the owner of this thumbnail is not, somehow, maintaining a strong reference to it (e.g., the owner, itself, has a retain cycle, or something like that).