如何释放CGContextDrawPDFPage创建的内存

Question

这是ipad杂志应用程序。我们需要阅读PDF和转换为缩略图PNG图像。在转换之前阅读PDF之后，调用了CGContextDrawPDFPage，内存迅速增加，直到崩溃才释放。我尝试了很多方法，但都不起作用。如果有人能帮上忙我真的很感激。

CGContextDrawPDFPage(context，aPage)；//这是内存杀手

以下是完整的代码：

-(UIImage *)图像:(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

您需要释放并重新打开此处解释的CGPDFDocument Fast and Lean PDF Viewer for iPhone / iPad / iOs - tips and hints?