How to free memory created by CGContextDrawPDFPage

Question

This app is for ipad magazine. We need to read the PDF and convert to a PNG image for thumnail. After reading the PDF before the conversion that calls CGContextDrawPDFPage, the memory rises quickly and is never freed until it crashes. I tried in many ways, but it did not work. I really appreciate if anyone can help.

CGContextDrawPDFPage (context, aPage); // this is a memory killer

Below is the full code:

- (UIImage *) image: (CGPDFPageRef) aPage rect: (CGRect) aRect {CGRect pdfcropBox = CGRectIntegral (CGPDFPageGetBoxRect (aPage, kCGPDFCropBox));

if ((float)pdfcropBox.size.width/(float)pdfcropBox.size.height > 
    (float)aRect.size.width/(float)aRect.size.height) //pdf width too big
{
    aRect.size.height = aRect.size.width * pdfcropBox.size.height / pdfcropBox.size.width;
}
//CGRect pdfcropBox = aRect;    

CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef context = CGBitmapContextCreate(NULL,aRect.size.width,
                                             aRect.size.height,
                                             8,
                                             (int)aRect.size.width * 4,
                                             colorSpace, 
                                             kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);

CGColorSpaceRelease(colorSpace);
colorSpace = nil;

CGPDFPageRetain(aPage);
CGAffineTransform pdfTransform = CGPDFPageGetDrawingTransform(aPage,
                                                              kCGPDFCropBox,
                                                              CGRectMake(0, 0, aRect.size.width,aRect.size.height),
                                                              0, true);
CGContextSaveGState(context);
CGContextConcatCTM(context, pdfTransform);
CGContextDrawPDFPage(context, aPage);
CGPDFPageRelease (aPage);
aPage = nil;
CGContextRestoreGState(context);    
CGImageRef image = CGBitmapContextCreateImage(context);
UIImage *resultingImage =  [UIImage imageWithCGImage:image];
CGContextClearRect(context, aRect);
CGContextClearRect(context, pdfcropBox);

CGContextRelease(context);
CGImageRelease(image);
context = nil; 

NSLog(@"colorSpace :%d,aPage :%d,context :%d",[colorSpace retainCount],[aPage retainCount],[context retainCount]);
return resultingImage;

}

Answer 1

CGPDFDocument, PDF- iPhone/iPad/iOs - ?