Quartz PDF API Causing Out of Memory Crashes

Question

I'm having crashing issues using the Quartz PDF API for iOS. At the moment I am compiling with the SDK 4.0 GM Seed and running on my 3.2 iPad (I have tried using the 3.2 SDK with identical results).

All the code I am using is based on the standard Apple Quartz documentation and from various sources around the internets. So I can't image I'm doing something drastically different or wrong.

The code runs perfectly in the Simulator (all versions, it's a Universal app) and even while using the "Simulate Memory Warning" function. I've used the Leaks tool and there are no leaks that it finds. Build and Analyze also finds nothing. No crash or low memory log is left in my Library.

All this leads me to believe the device is running out of memory. This happens after running through say 50 pdf pages, with about 35% having an image of some sort (some full page some icon). It does not crash on any particular page. The pdf I am loading is about 75 pages and 3.5MB.

I've perused similar issues on this site and around the internets, and have applied some of the advice in the code below. I now release the pdf document reference on every page turn and I no longer retain/release a page reference. I've also simplified the image swapping from using CGImages to just using the UIGraphicsGetImageFromCurrentImageContext function. I've tried various implementations for switching the images, including replacing the pdfImgView completely with a newly allocated temp instance (using [[UIImageView alloc] iniWithImage:UIGraphicsGetImageFromCurrentImageContext()]), using the setter for pdfImgView and releasing the temp. All of the variations pass the Leaks and Analyzer tests, but still exhibit the same crashing behavior.

So, before I move away from PDFs altogether, is there something I should try or something I am missing?

View controller code that is called in interface handlers to swap pages and on first load:

[self drawPage];

// ...animation code...simple CATransition animation...crashes with or without

// scrollView is a UIScrollView that is a subview of self.view
[scrollView.layer addAnimation:transition forKey:nil];
// pdfImgView is a UIImageView that is a subview of scrollView
pdfImgView.image = UIGraphicsGetImageFromCurrentImageContext();

drawPage method used to configure and draw PDF page to the context:

[CFURLRef pdfURL = CFBundleCopyResourceURL(CFBundleGetMainBundle(), CFSTR("BME_interior.pdf"), NULL, NULL);
pdfRef = CGPDFDocumentCreateWithURL((CFURLRef)pdfURL); // instance variable, not a property
CFRelease(pdfURL);
CGPDFPageRef page = CGPDFDocumentGetPage(pdfRef, currentPage);

CGRect box = CGPDFPageGetBoxRect(page, kCGPDFMediaBox);
// ...setting scale and imageHeight, both floats...

if (UIGraphicsBeginImageContextWithOptions != NULL) {
    UIGraphicsBeginImageContextWithOptions(CGSizeMake(self.view.frame.size.width, imageHeight), NO, 0.0);
} else {
    UIGraphicsBeginImageContext(CGSizeMake(self.view.frame.size.width, imageHeight));
}
CGContextRef context = UIGraphicsGetCurrentContext();
NSLog(@"page is %d, context is %d, pdf doc is %d, pdf page is %d", currentPage, context, pdfRef, page); // all prints properly

// ...setting up scrollView for new page, using same instance...

CGContextTranslateCTM(context, (self.view.frame.size.width-(box.size.width*scale))/2.0f, imageHeight);
CGContextScaleCTM(context, scale, -1.0*scale);

CGContextSaveGState(context);
CGContextDrawPDFPage(context, page);
CGContextRestoreGState(context);

CGPDFDocumentRelease(pdfRef);
pdfRef = NULL;

Answer 1

Aha! I've fixed the crashes by adding a UIGraphicsEndImageContext(); before beginning a new image context. I don't even get memory warnings now...

Answer 2

Calling

CGContextSetInterpolationQuality(context, kCGInterpolationHigh); 
CGContextSetRenderingIntent(context, kCGRenderingIntentDefault);

before CGContextDrawPDFPage solved a similar problem of mine.

Credits goes to this answer of Johann: CGContextDrawPDFPage taking up large amounts of memory