使用Swift裁剪图像并将其置于中心位置

Question

在Swift编程中，如何裁剪图像，然后将其放在中心？

到目前为止，这就是我要做的…我已经成功裁剪了图像，但是我想在之后将其放在中间

ImgView.image = OrigImage
var masklayer = CAShapeLayer()
masklayer.frame = ImgView.frame
masklayer.path = path.CGPath
masklayer.fillColor = UIColor.whiteColor().CGColor
masklayer.backgroundColor = UIColor.clearColor().CGColor

ImgView.layer.mask = masklayer

UIGraphicsBeginImageContext(ImgView.bounds.size);
ImgView.layer.renderInContext(UIGraphicsGetCurrentContext())
var image = UIGraphicsGetImageFromCurrentImageContext()
ImgView.image = image
UIGraphicsEndImageContext();

更新：

let rect: CGRect = CGRectMake(path.bounds.minX, path.bounds.minY, path.bounds.width, path.bounds.height)

// Create bitmap image from context using the rect
let imageRef: CGImageRef = CGImageCreateWithImageInRect(image.CGImage, rect)
ImgView.bounds = rect
ImgView.image = UIImage(CGImage: imageRef)

我可以通过获取path.bound和size来居中，并更改ImageView的边界。:)

Answer 1

要获得作物的居中位置，可以将高度和宽度的差减半。然后，您可以在检查图像的方向（较长的部分）后为新的宽度和高度指定边界

func cropToBounds(image: UIImage, width: Double, height: Double) -> UIImage {

    let contextImage: UIImage = UIImage(CGImage: image.CGImage)!

    let contextSize: CGSize = contextImage.size

    var posX: CGFloat = 0.0
    var posY: CGFloat = 0.0
    var cgwidth: CGFloat = CGFloat(width)
    var cgheight: CGFloat = CGFloat(height)

    // See what size is longer and create the center off of that
    if contextSize.width > contextSize.height {
        posX = ((contextSize.width - contextSize.height) / 2)
        posY = 0
        cgwidth = contextSize.height
        cgheight = contextSize.height
    } else {
        posX = 0
        posY = ((contextSize.height - contextSize.width) / 2)
        cgwidth = contextSize.width
        cgheight = contextSize.width
    }

    let rect: CGRect = CGRectMake(posX, posY, cgwidth, cgheight)

    // Create bitmap image from context using the rect
    let imageRef: CGImageRef = CGImageCreateWithImageInRect(contextImage.CGImage, rect)

    // Create a new image based on the imageRef and rotate back to the original orientation
    let image: UIImage = UIImage(CGImage: imageRef, scale: image.scale, orientation: image.imageOrientation)!

    return image
}

我在本网站上找到了大部分此类信息，以防您想进一步阅读。

为 Swift 4* 更新 *

func cropToBounds(image: UIImage, width: Double, height: Double) -> UIImage {

        let cgimage = image.cgImage!
        let contextImage: UIImage = UIImage(cgImage: cgimage)
        let contextSize: CGSize = contextImage.size
        var posX: CGFloat = 0.0
        var posY: CGFloat = 0.0
        var cgwidth: CGFloat = CGFloat(width)
        var cgheight: CGFloat = CGFloat(height)

        // See what size is longer and create the center off of that
        if contextSize.width > contextSize.height {
            posX = ((contextSize.width - contextSize.height) / 2)
            posY = 0
            cgwidth = contextSize.height
            cgheight = contextSize.height
        } else {
            posX = 0
            posY = ((contextSize.height - contextSize.width) / 2)
            cgwidth = contextSize.width
            cgheight = contextSize.width
        }

        let rect: CGRect = CGRect(x: posX, y: posY, width: cgwidth, height: cgheight)

        // Create bitmap image from context using the rect
        let imageRef: CGImage = cgimage.cropping(to: rect)!

        // Create a new image based on the imageRef and rotate back to the original orientation
        let image: UIImage = UIImage(cgImage: imageRef, scale: image.scale, orientation: image.imageOrientation)

        return image
    }