如何裁剪給定的圖像視圖

Question

我想在uiimagepickercontrollers overlayView上顯示裁剪視圖，然后相對於overlayImage rect裁剪圖像。 給定overlayView的矩形，如何計算裁剪圖像？

Answer 1

private func CropImage( image:UIImage , cropRect:CGRect) -> UIImage
{
    UIGraphicsBeginImageContextWithOptions(cropRect.size, false, 0);
    let context = UIGraphicsGetCurrentContext();

    context?.translateBy(x: 0.0, y: image.size.height);
    context?.scaleBy(x: 1.0, y: -1.0);
    context?.draw(image.cgImage!, in: CGRect(x:0, y:0, width:image.size.width, height:image.size.height), byTiling: false);
    context?.clip(to: [cropRect]);

    let croppedImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return croppedImage!;
}

Answer 2

您可以使用下面的代碼塊來實現。

let imageRef:CGImage = uncroppedImage.cgImage!.cropping(to: bounds)!
let croppedImage:UIImage = UIImage(cgImage: imageRef)

在這里，您可以根據自己的要求通過您的矩形。

您也可以按照蘋果的建議進行操作。

請找到官方文檔。

func cropImage(_ inputImage: UIImage, toRect cropRect: CGRect, viewWidth: CGFloat, viewHeight: CGFloat) -> UIImage? 
{    
    let imageViewScale = max(inputImage.size.width / viewWidth,
                             inputImage.size.height / viewHeight)

    // Scale cropRect to handle images larger than shown-on-screen size
    let cropZone = CGRect(x:cropRect.origin.x * imageViewScale,
                          y:cropRect.origin.y * imageViewScale,
                          width:cropRect.size.width * imageViewScale,
                          height:cropRect.size.height * imageViewScale)

    // Perform cropping in Core Graphics
    guard let cutImageRef: CGImage = inputImage.cgImage?.cropping(to:cropZone)
    else {
        return nil
    }

    // Return image to UIImage
    let croppedImage: UIImage = UIImage(cgImage: cutImageRef)
    return croppedImage
}