Iphone 裁剪图像截图

我目前正在替换代码中的UIGetScreenImage（），因为它会导致C99错误

我将它替换为，

screenshot

方法返回一个

UIImage

我尝试裁剪和保存图像如下：

UIImage *returnedImage = [self screenshot];
// Get image to save
CGImageRef screen = returnedImage.CGImage;
UIImage *img = [UIImage imageWithCGImage:screen];

// Image cropping
CGImageRef imageRef = CGImageCreateWithImageInRect([img CGImage], CGRectMake(0, 5, 768, 1004));
UIImage *img2Save = [UIImage imageWithCGImage:imageRef];
CGImageRelease(imageRef);

// Request to save the image to camera roll
UIImageWriteToSavedPhotosAlbum(img2Save, self, nil, nil);

在返回它之前，我还尝试过在

屏幕截图
方法中裁剪它，但没有效果

两次尝试都会保存从
屏幕截图
方法返回的未截取的
UIImage

有什么明显的东西我漏掉了吗？我已查看，但看不到连接。
请尝试以下代码

- (UIImage*)imageByCropping:(UIImage *)imageToCrop toRect:(CGRect)rect
{
   //create a context to do our clipping in
   UIGraphicsBeginImageContext(rect.size);
   CGContextRef currentContext = UIGraphicsGetCurrentContext();

   //create a rect with the size we want to crop the image to
   //the X and Y here are zero so we start at the beginning of our
   //newly created context
   CGRect clippedRect = CGRectMake(0, 0, rect.size.width, rect.size.height);
   CGContextClipToRect( currentContext, clippedRect);

   //create a rect equivalent to the full size of the image
   //offset the rect by the X and Y we want to start the crop
   //from in order to cut off anything before them
   CGRect drawRect = CGRectMake(rect.origin.x * -1,
                                rect.origin.y * -1,
                                imageToCrop.size.width,
                                imageToCrop.size.height);

   //draw the image to our clipped context using our offset rect
   CGContextDrawImage(currentContext, drawRect, imageToCrop.CGImage);

   //pull the image from our cropped context
   UIImage *cropped = UIGraphicsGetImageFromCurrentImageContext();

   //pop the context to get back to the default
   UIGraphicsEndImageContext();

   //Note: this is autoreleased
   return cropped;
}

然后用如下方法调用代码：

- (void)drawRect:(CGRect)rect
{
   //draw the whole lights off image
   //the on images will be drawn overtop
   [lightsOffImage drawInRect:rect];

   //if we don't have any lights on... no point in continuing
   if( numberOfLightsOn < 1 )
     return;

   //figure out the dimensions of numberOfLights on bulbs
   CGSize croppedSize = CGSizeMake(LIGHT_WIDTH * numberOfLightsOn, LIGHT_HEIGHT);
   CGRect clippedRect = CGRectMake(0, 0, croppedSize.width, croppedSize.height);

   //get the "on" bulbs by cropping the image
   UIImage *cropped = [self imageByCropping:lightsOnImage toRect:clippedRect];

   //create a rect to draw the newly cropped on images to
   CGRect lightsOnRect = CGRectMake(LIGHT_BULB_OFFSET_X,
                                    LIGHT_BULB_OFFSET_Y,
                                    croppedSize.width,
                                    croppedSize.height);

   //draw the "on" lights
   [cropped drawInRect:lightsOnRect];

   //cropped is autoreleased so no need to worry about cleanup
}

-（void）drawRect:（CGRect）rect
{
//画出整个灯光关闭图像
//图像上的图像将绘制在顶部
[lightsOffImage drawInRect:rect]；
//如果我们没有任何灯亮着…继续下去就没有意义了
if（numberOfLightsOn<1）
返回；
//算出灯泡上的灯数的尺寸
CGSize CROPTEDSIZE=CGSizeMake（灯光宽度*灯光数量、灯光高度）；
CGRect CLIPEDRECT=CGRectMake（0,0，croppedSize.width，croppedSize.height）；
//通过裁剪图像获得“开启”灯泡
UIImage*cropped=[自映像通过裁剪：lightsOnImage toRect:clippedRect]；
//创建一个矩形以绘制新裁剪的图像
CGRect lightsOnRect=CGRectMake（灯泡偏移量），
灯泡偏移量，
croppedSize.width，
裁剪尺寸、高度）；
//绘制“打开”灯
[裁剪图纸，包括：lightsOnRect]；
//裁剪是自动删除的，因此无需担心清理
}

希望这段代码能对您有所帮助。
Hi@neon samuel，我曾尝试从另一个so线程调用该函数。发生的情况是，它似乎颠倒了图片并缩小了图像。这是因为我传递给它的坐标吗？我认为它不会倒过来，因为我传递给该方法的前两个参数是0。