iOS、Swift、UIImagePicker 允许编辑裁剪工具移除透明度。有修吗？

Question

当我从 UIImagePicker 获取具有透明背景的 PNG 图像时，它会插入具有透明背景的图像，如下所示:

当我设置时:

imagePicker.allowsEditing = true

它允许我在 UIImagePicker 提供的 View 中按预期裁剪

但是当我按下“选择”时，它会返回黑色而不是透明背景的图像，如下所示:

两个结果之间唯一的变化是设置

imagePicker.allowsEditing = true

并在应用中裁剪图像。

有没有办法在裁剪时保持透明度或至少将黑色变为白色？

我已经在互联网上搜索过，但没有提到我能看到的。

代码:

 func showImagePicker() {
    imagePicker.allowsEditing = true
    imagePicker.sourceType = .photoLibrary

    present(imagePicker, animated: true, completion: nil)
}

func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any]) {
    if let pickedImage = info[UIImagePickerControllerEditedImage] as? UIImage {
        compImageView?.contentMode = .scaleAspectFit
        compImageView?.backgroundColor = UIColor.clear
        compImageView?.image = pickedImage

    }

    dismiss(animated: true, completion: nil)
}

Answer 1

默认情况下，UIImagePickerController 会移除已编辑图像中的 alpha channel 。要获得这种透明度，您必须自己编辑图像。像这样实现委托(delegate)方法:

func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any]) {


        if let cropRect = info[UIImagePickerControllerCropRect] as? CGRect {
            if let image = info[UIImagePickerControllerOriginalImage] as? UIImage {
                let imageRef: CGImage = image.cgImage!.cropping(to: cropRect)!

                let image1: UIImage = UIImage(cgImage: imageRef, scale: image.scale, orientation: image.imageOrientation)

                imageView.image = image1
                picker.dismiss(animated: true, completion: nil)

            }

        }

    }