从中心向外裁剪 UIImage？

Question

我正在制作一个包含数字变焦的相机应用程序。我有一个滑块 (zoomSlider)，其最小值为 1，最大值为 4。当用户点击相机按钮时，它会拍摄一张照片，然后我对其进行裁剪以进行缩放。我有两个问题：

如何裁剪图像的中间部分？ （例如，2 倍缩放，矩形将以 600x800 的尺寸居中（对于 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，但这会导致纵向图片变成横向图片，反之亦然。

这是我的代码：

- (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;

}

Answer 1

CGFloat newWidth = image.size.width/zoomSlider.value;
CGFloat newHeight = image.size.height/zoomSlider.value;

CGRect clippedRect = CGRectMake((image.size.width-newWidth)/2, (image.size.height-newHeight)/2, newWidth, newHeight);

删除它以不旋转图像：

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

zoomPhoto.transform = rotateTransform;