在共享扩展中旋转图像

Question

我有这个扩展程序，它在应用程序目标中运行良好，但在尝试旋转相机上捕获的图像时在共享扩展程序中崩溃。如何在共享扩展中旋转图像？或者也许可以从照片库中加载图像已经在正确的方向。

extension UIImage {

    func fixOrientation() -> UIImage {
        switch imageOrientation {
        case .up:
            return self
        default:
            UIGraphicsBeginImageContextWithOptions(size, false, scale)
            draw(in: CGRect(origin: .zero, size: size)) //Thread 1: EXC_RESOURCE RESOURCE_TYPE_MEMORY (limit=120 MB, unused=0x0)
            let result = UIGraphicsGetImageFromCurrentImageContext()
            UIGraphicsEndImageContext()
            return result!
        }
    }
}

崩溃截图：

Answer 1

首先很明显你有内存崩溃。根据App Extension Programming Guide：

运行应用扩展的内存限制明显低于前台应用的内存限制。在这两个平台上，系统都可能会因为用户想要返回到他们在宿主应用中的主要目标而主动终止扩展。

从错误中很明显你超过了 120 mb。但您可能想知道是什么占用了这么多内存。

根据Optimizing Images Written by Jordan Morgan：

iOS 本质上是从图像的尺寸中获取其内存影响 - 而实际文件大小与它的关系要小得多。

因此，如果我们计算尺寸或 4032 x 3024 照片，它将是...... 4 位颜色为 46mb，8 位颜色为 79mb。相当大，但仍然没有限制......

问题是 - 您有 两个 图像副本。一个是原始的，第二个是旋转的。

要解决此问题，您只需将旋转后的图像加载到内存中，而不需要原始图像。这可以通过Image I/O Framework 来完成：

extension UIImage {
    static func imageWithFixedOrientation(at url: URL) -> UIImage? {
        guard let imageSource = CGImageSourceCreateWithURL(url as CFURL, nil) else { return nil }

        guard let imageProperties = CGImageSourceCopyPropertiesAtIndex(imageSource, 0, nil) as? Dictionary<CFString, Any> else { return nil }

        guard
            let width = imageProperties[kCGImagePropertyPixelWidth] as? CGFloat,
            let height = imageProperties[kCGImagePropertyPixelHeight] as? CGFloat
            else { return nil }

        let options: [NSString: Any] = [
            kCGImageSourceThumbnailMaxPixelSize: max(width, height),
            kCGImageSourceCreateThumbnailFromImageAlways: true,
            kCGImageSourceCreateThumbnailWithTransform: true
        ]

        guard let cgImage = CGImageSourceCreateThumbnailAtIndex(imageSource, 0, options as CFDictionary) else { return nil }

        return UIImage(cgImage: cgImage)
    }
}

在示例应用中：

extension ViewController: UIImagePickerControllerDelegate & UINavigationControllerDelegate {
    func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [UIImagePickerController.InfoKey : Any]) {
        picker.dismiss(animated: true)
        guard let url = info[.imageURL] as? URL else { return }

        let image = UIImage.imageWithFixedOrientation(at: url)
    }
}

它将内存峰值从 180+mb 减少到仅 80mb。

Answer 2

您可以尝试使用更优化的UIGraphicsImageRendererFormat，而不是使用旧的UIGraphicsBeginImageContextWithOptions，您可以在此post 中找到更多信息。因此您的代码将如下所示：

func fixOrientation() -> UIImage {
    let format = UIGraphicsImageRendererFormat()
    format.scale = scale
    format.prefersExtendedRange = true
    let renderer = UIGraphicsImageRenderer(size: size, format: format)
    let image = renderer.image(actions: { context in

        var workSize = size;
        workSize.width = floor(workSize.width / scale)
        workSize.height = floor(workSize.height / scale)

        // if the orientation is already correct
        // if image.imageOrientation == .up { draw image }

        var transform = CGAffineTransform.identity

        //TO-DO - set transform depends on current image orientation
        //transform =

        let ctx = context.cgContext
        ctx.concatenate(transform)

        guard let cgImageCopy = cgImage else {
            return
        }

        switch imageOrientation {
        case .left, .leftMirrored, .right, .rightMirrored:
            ctx.draw(cgImageCopy, in: CGRect(x: 0.0, y:0.0, width: workSize.height, height: workSize.width))
            break;

        default:
            ctx.draw(cgImageCopy, in: CGRect(origin: .zero, size: workSize))
            break;
        }
    })

    return image
}

Answer 3

您是否尝试使用您在 didFinishPicking 委托方法中提供的函数？

func photoLibrary() {
    if UIImagePickerController.isSourceTypeAvailable(.photoLibrary) {
        let myPickerController = UIImagePickerController()
        myPickerController.delegate = self
        myPickerController.sourceType = .photoLibrary
        self.present(myPickerController, animated: true, completion: nil)
    }
}

func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [UIImagePickerController.InfoKey : Any]) {
    picker.dismiss(animated: true)

    guard let image = info[.originalImage] as? UIImage else {
        print("No image found")
        return
    }

    // Flip the image here
    self.mainImageView.image = image.fixOrientation()
}