无法获取 UIImage 以匹配自定义 ImagePickerController 预览

Posted 2023-02-23

【中文标题】无法获取 UIImage 以匹配自定义 ImagePickerController 预览

【英文标题】：Unable To Get UIImage to Match Custom ImagePickerController Preview

【发布时间】：2015-04-26 17:38:48

【问题描述】：

我正在构建一个具有全屏 ImagePickerController 的 ios 应用程序，捕获的结果图像与 ImagePickerController 视图中显示的图像相同。这是我当前的相关代码：

创建和转换 ImagePickerController：

    self.imagePicker = [[UIImagePickerController alloc] init];
self.imagePicker.delegate = self;


CGSize screenSize = [[UIScreen mainScreen] bounds].size;

// set the aspect ratio of the camera
float heightRatio = 4.0f / 3.0f;
// calculate the height of the camera based on the screen width
float cameraHeight = floorf(screenSize.width * heightRatio);
// calculate the ratio that the camera height needs to be scaled by
float scale = ceilf((screenSize.height / cameraHeight) * 10.0) / 10.0;

if ([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera]) 
    self.imagePicker.sourceType = UIImagePickerControllerSourceTypeCamera;


    self.imagePicker.showsCameraControls = NO;
    [self.imagePicker setCameraOverlayView:cameraView];

    // move the controller to the center of the screen
    self.imagePicker.cameraViewTransform = CGAffineTransformMakeTranslation(0, (screenSize.height - cameraHeight) / 2.0);
    // concatenate the scale transform
    self.imagePicker.cameraViewTransform = CGAffineTransformScale(self.imagePicker.cameraViewTransform, scale, scale);

捕获图像后，这是我用来重绘捕获的图像以匹配预览的代码：

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info 
NSString *mediaType = [info objectForKey:UIImagePickerControllerMediaType];
 self.image = [info objectForKey:UIImagePickerControllerOriginalImage];
 self.image = [self croppedImage:self.image];

- (UIImage *) croppedImage: (UIImage *)image

CGSize screenSize = [[UIScreen mainScreen] bounds].size;    
// set the aspect ratio of the camera
float heightRatio = 4.0f / 3.0f;
// calculate the height of the camera based on the screen width
float cameraHeight = floorf(screenSize.width * heightRatio);
// calculate the ratio that the camera height needs to be scaled by
float scale = ceilf((screenSize.height / cameraHeight) * 10.0) / 10.0;


CGSize originalImageSize = [image size];
CGSize newImageSize = CGSizeMake(floorf(originalImageSize.width / scale)* 3/4, floorf(originalImageSize.height / scale)* 3/4);

CGRect newImageRect = CGRectMake((originalImageSize.width - newImageSize.width)/2.0, (originalImageSize.height - newImageSize.height)/2.0, newImageSize.width, newImageSize.height);

return [image croppedImage:newImageRect];

所以我的问题是我的 CroppedImage 方法计算不正确，因为生成的图像似乎比需要的更“放大”。不太确定计算中有什么问题。

注意 - 此应用旨在在所有 iPhone 上正确缩放 - 仅限纵向模式。我目前正在 iPhone 6 上进行测试。

【参考方案1】：

如果这对任何人都有帮助 - 在我的设备上，我可以通过切换来修复它

       CGSize newImageSize = CGSizeMake(floorf(originalImageSize.width / scale)* 3/4, floorf(originalImageSize.height / scale)* 3/4);

到

       CGSize newImageSize = CGSizeMake(floorf(originalImageSize.width / scale), floorf(originalImageSize.height / scale)* 4/3);

只有需要乘以 4/3 而不是 3/4 的高度/比例。我还没有在任何其他设备上测试过这个。只是想这可能会帮助任何遇到同样事情的人。