设置UIImagePickerController裁剪的最小缩放级别

Question

我正在使用UIImagePickerController来允许用户上传照片以供我的应用程序使用。选择要上传的照片后，用户将被提示裁剪他/她的照片（因为我设置了imagePickerController.allowsEditing = YES）。但是，如果照片是横向的（即宽度大于高度），则目前用户可以按照不输出正方形图像的方式裁剪照片。这是因为在裁剪横向照片时，默认缩放级别是aspectFit而不是portrait photos所使用的aspectFill。

是否可能设置UIImagePickerController编辑模式的最小缩放级别？我想，如果输出不是正方形，我可以简单地自动裁剪图像，但我宁愿UIImagePickerController的编辑模式将此传达给用户，而不是为他/她完成此操作。

- Ken M. Haggerty

Answer 1

无法以支持的方式调整UIImagePickerController裁剪/编辑功能的行为。您可以潜入UIImagePickerController控制器/视图层次结构并尝试弄清楚它的工作原理，但这不是一件易于维护或愉快的事情。

话虽如此，UIImagePickerController是UINavigationController的子类，因此您可以实现自己的图像编辑视图控制器并将其推送到UIImagePickerController上。这可能不太难，您可以使用矩形覆盖层将选择的UIImage放入UIScrollView中，进行一些数学计算，然后自己裁剪UIImage。在这种情况下，您显然可以完全控制功能，并且我敢打赌，它需要的时间比深入研究UIImagePickerController的内部要少。

我可能会像这样设置呈现选择器的任何视图控制器：

@interface MainViewController <UIImagePickerControllerDelegate, UINavigationControllerDelegate, ImageEditorViewControllerDelegate>
@end

@implementation MainViewController {
    UIImagePickerController* _imagePickerController;
}
#pragma mark IBAction
- (IBAction)pickImage:(id)sender {
    _imagePickerController = [[UIImagePickerController alloc] init];
    _imagePickerController.delegate = self;
    _imagePickerController.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
    _imagePickerController.allowsEditing = NO;

    [self presentViewController:_imagePickerController animated:YES completion:nil];
}


#pragma mark UIImagePickerControllerDelegate
- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info {
    ImageEditorViewController* imageEditorViewController = [self.storyboard instantiateViewControllerWithIdentifier:@"ImageEditor"];
    imageEditorViewController.delegate = self;
    imageEditorViewController.imageToEdit = info[UIImagePickerControllerOriginalImage];

    [_imagePickerController pushViewController:imageEditorViewController animated:YES];
}


- (void)imagePickerControllerDidCancel:(UIImagePickerController *)picker {
    [self dismissViewControllerAnimated:YES completion:^{
        _imagePickerController = nil;
    }];
}


#pragma mark ImageEditorViewControllerDelegate
- (void)imageEditorViewController:(ImageEditorViewController *)imageEditorViewController didFinishWithInfo:(NSDictionary *)info {
    // TODO: Handle the edited media

    [self dismissViewControllerAnimated:YES completion:^{
        _imagePickerController = nil;
    }];
}
@end

然后您的编辑视图将具有如下接口（根据您的需求进行特定实现）：

@protocol ImageEditorViewControllerDelegate;

@interface ImageEditorViewController : UIViewController
@property(nonatomic, strong) UIImage* imageToEdit;

@property(nonatomic, weak) id <ImageEditorViewControllerDelegate> delegate;
@end

@protocol ImageEditorViewControllerDelegate
- (void)imageEditorViewController:(ImageEditorViewController*)imageEditorViewController didFinishWithInfo:(NSDictionary*)info;
@end

- Charles A.