多个图像操作崩溃iPhone应用程序

Question

我是iPhone应用程序开发的新手,所以我可能做错了.

基本上,我正在从互联网上加载一堆图像,然后裁剪它们.我设法找到了异步加载图像并将它们添加到视图中的示例.我已经设法通过添加一个图像NSData,通过a NSOperation,添加到一个NSOperationQueue.

然后,因为我必须制作固定大小的拇指,我需要一种方法来裁剪这些图像,所以我在网上发现了一个基本上使用的脚本UIGraphicsBeginImageContext(),UIGraphicsGetImageFromCurrentImageContext()并UIGraphicsEndImageContext()绘制裁剪的图像,以及不重要​​的大小计算.

问题是,该方法有效,但由于它生成了20个这样的图像,它会在生成一些图像之后随机崩溃,或者有时在我关闭并重新打开应用程序一两次之后.

在这种情况下我该怎么办？我试图使这个方法异步运行不知何故,以及与NSOperations和NSOperationQueue,但没有运气.

如果裁剪代码比我想的更相关,那么它是:

UIGraphicsBeginImageContext(CGSizeMake(50, 50));
CGRect thumbnailRect = CGRectZero;
thumbnailRect.origin = CGPointMake(0.0,0.0); //this is actually generated
                                             // based on the sourceImage size
thumbnailRect.size.width  = 50;
thumbnailRect.size.height = 50;
[sourceImage drawInRect:thumbnailRect];
newImage = UIGraphicsGetImageFromCurrentImageContext();

谢谢!

Answer 1

缩放图像的代码看起来太简单了.这是我正在使用的那个.如您所见,没有泄漏,不再需要时释放对象.希望这可以帮助.

    // Draw the image into a pixelsWide x pixelsHigh bitmap and use that bitmap to 
// create a new UIImage 
- (UIImage *) createImage: (CGImageRef) image width: (int) pixelWidth height: (int) pixelHeight
{ 
    // Set the size of the output image 
    CGRect aRect = CGRectMake(0.0f, 0.0f, pixelWidth, pixelHeight); 
    // Create a bitmap context to store the new thumbnail 
    CGContextRef context = MyCreateBitmapContext(pixelWidth, pixelHeight); 
    // Clear the context and draw the image into the rectangle 
    CGContextClearRect(context, aRect); 
    CGContextDrawImage(context, aRect, image); 
    // Return a UIImage populated with the new resized image 
    CGImageRef myRef = CGBitmapContextCreateImage (context); 

    UIImage *img = [UIImage imageWithCGImage:myRef];

    free(CGBitmapContextGetData(context)); 
    CGContextRelease(context);
    CGImageRelease(myRef);

    return img; 
} 


// MyCreateBitmapContext: Source based on Apple Sample Code
CGContextRef MyCreateBitmapContext (int pixelsWide,
                                    int pixelsHigh)
{
    CGContextRef    context = NULL;
    CGColorSpaceRef colorSpace;
    void *          bitmapData;
    int             bitmapByteCount;
    int             bitmapBytesPerRow;

    bitmapBytesPerRow   = (pixelsWide * 4);
    bitmapByteCount     = (bitmapBytesPerRow * pixelsHigh);

    colorSpace = CGColorSpaceCreateDeviceRGB();
    bitmapData = malloc( bitmapByteCount );
    if (bitmapData == NULL)
    {
        fprintf (stderr, "Memory not allocated!");
        CGColorSpaceRelease( colorSpace );
        return NULL;
    }
    context = CGBitmapContextCreate (bitmapData,
                                     pixelsWide,
                                     pixelsHigh,
                                     8,
                                     bitmapBytesPerRow,
                                     colorSpace,
                                     kCGImageAlphaPremultipliedLast);
    if (context== NULL)
    {
        free (bitmapData);
        CGColorSpaceRelease( colorSpace );
        fprintf (stderr, "Context not created!");
        return NULL;
    }
    CGColorSpaceRelease( colorSpace );

    return context;
}