Iphone 从中心向外裁剪UIImage？

我正在制作一个包括数码变焦的相机应用程序。我有一个滑块（zoomSlider），最小值为1，最大值为4。当用户点击相机按钮时，它会拍摄一张照片，然后我将其裁剪以进行缩放。我有两个问题：

如何裁剪图像的中间部分？（例如，2x缩放，Rect将以600x800的尺寸居中（适用于iPhone 2G/3G））

当我这样做时，它会旋转图像。我通过旋转它所在的UIImageView来弥补它，但这会导致肖像画变成风景画，反之亦然

这是我的密码：

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info {

     if ([mediaType isEqualToString:@"public.image"]){

UIImage *image = [info objectForKey:@"UIImagePickerControllerOriginalImage"];

          CGRect clippedRect = CGRectMake(600, 450, image.size.width/zoomSlider.value, image.size.height/zoomSlider.value);

          UIImage *cropped = [self imageByCropping:image toRect:clippedRect];

          CGRect croppedImageSize = CGRectMake(0, 0, image.size.width/zoomSlider.value, image.size.height/zoomSlider.value);

          [cropped drawInRect:croppedImageSize];

          zoomPhoto.frame = croppedImageSize;

          zoomPhoto.image = cropped;

CGAffineTransform rotateTransform = CGAffineTransformRotate(CGAffineTransformIdentity,

                                                                                     RADIANS(90.0));

          zoomPhoto.transform = rotateTransform;
}

- (UIImage *)imageByCropping:(UIImage *)imageToCrop toRect:(CGRect)rect

{

     CGImageRef imageRef = CGImageCreateWithImageInRect([imageToCrop CGImage], rect);



     UIImage *cropped = [UIImage imageWithCGImage:imageRef];

CGImageRelease(imageRef);




 return cropped;

}

删除此选项以不旋转图像：

CGAffineTransform rotateTransform = CGAffineTransformRotate(CGAffineTransformIdentity,RADIANS(90.0));

zoomPhoto.transform = rotateTransform;

删除此选项以不旋转图像：

CGAffineTransform rotateTransform = CGAffineTransformRotate(CGAffineTransformIdentity,RADIANS(90.0));

zoomPhoto.transform = rotateTransform;