从 AVCapturePhotoOutput 裁剪 CGRect (resizeAspectFill)

Question

我发现了以下问题，不幸的是其他帖子没有帮助我找到有效的解决方案。

我有一个简单的应用程序可以显示相机预览 (AVCaptureVideoPreviewLayer)，其中视频重力已设置为 resizeAspectFill (videoGravity = .resizeAspectFill)。

据我了解，这只会拉伸图像的宽度以填满屏幕。

在我的预览层上，我还应用了 CGRect 作为具有固定 x、y、宽度和高度的遮罩。

现在，一旦我拍完照片，我就会尝试从图像中裁剪出那个确切的矩形。据我了解，我应该使用某种数学方法将 CGRect 转换为与我从 AVCapturePhotoOutput 方法获得的图像相同的宽高比，但它似乎从未在宽度上正确裁剪。

    private func cropImage(image: UIImage) {
        let rect = CGRect(x: 25, y: 150, width: 325, height: 230)
        
        
        let scale = CGAffineTransform(scaleX: 1/self.view.frame.width, y: 1/self.view.frame.height)
        let flip = CGAffineTransform(scaleX: 1, y: -1).translatedBy(x: 0, y: -1)
        
        let bounds = rect.applying(scale).applying(flip)
        
        
        let topLeft = bounds.topLeft.scaled(to: image.size)
        let topRight = bounds.topRight.scaled(to: image.size)
        let bottomLeft = bounds.bottomLeft.scaled(to: image.size)
        let bottomRight = bounds.bottomRight.scaled(to: image.size)
        
        var ciImage = CIImage(image: image.forceSameOrientation())!
        
        ciImage = ciImage.applyingFilter("CIPerspectiveCorrection", parameters: [
            "inputTopLeft": CIVector(cgPoint: bottomLeft),
            "inputTopRight": CIVector(cgPoint: bottomRight),
            "inputBottomLeft": CIVector(cgPoint: topLeft),
            "inputBottomRight": CIVector(cgPoint: topRight)
        ])
        
        let context = CIContext()
        let cgImage = context.createCGImage(ciImage, from: ciImage.extent)
        let output = UIImage(cgImage: cgImage!)
        
        
        let vc = PreviewViewController()
        vc.imageView.image = output
        self.present(vc, animated: true, completion: nil)
    }

所以，基本上它确实在正确的高度裁剪，但它只是宽度似乎不太好。

我想要捕捉的图片示例。

https://imgur.com/a/8GryEgX

如您所见，左上角的边界框在“Q”按钮后停止。

结果：

https://imgur.com/FwKRWxK

正如您在这张图片中看到的，它确实在高度上正确裁剪了，但是如果我们看一下左上角，它还包括“Q”（Tab 按钮）左侧的一半按钮

任何对解决方案的帮助将不胜感激！

Answer 1

我设法用这段代码解决了问题。

private func cropToPreviewLayer(from originalImage: UIImage, toSizeOf rect: CGRect) -> UIImage? {
    guard let cgImage = originalImage.cgImage else { return nil }

    // This previewLayer is the AVCaptureVideoPreviewLayer which the resizeAspectFill and videoOrientation portrait has been set.
    let outputRect = previewLayer.metadataOutputRectConverted(fromLayerRect: rect)

    let width = CGFloat(cgImage.width)
    let height = CGFloat(cgImage.height)

    let cropRect = CGRect(x: (outputRect.origin.x * width), y: (outputRect.origin.y * height), width: (outputRect.size.width * width), height: (outputRect.size.height * height))

    if let croppedCGImage = cgImage.cropping(to: cropRect) {
        return UIImage(cgImage: croppedCGImage, scale: 1.0, orientation: originalImage.imageOrientation)
    }

    return nil
}

这段代码在我的案例中的用法：

let rect = CGRect(x: 25, y: 150, width: 325, height: 230)
let croppedImage = self.cropToPreviewLayer(from: image, toSizeOf: rect)
self.imageView.image = croppedImage

从 AVCapturePhotoOutput 裁剪 CGRect (resizeAspectFill)

Cropping CGRect from AVCapturePhotoOutput (resizeAspectFill)

swift

crop

cgrect

avcapturephotooutput