如何确定用户在UIImage上点击了哪个像素(x，y)? [英] How to determine what pixel (x, y) user tapped on a UIImage?

问题描述

我有一个UIImageView.我添加一张图片，然后点击图片的某些位置.

I have a UIImageView. I add an image and tap on some where of image.

有什么方法可以确定点击的图像的像素(x，y)?

Is there any way to determine what is the pixel (x,y) of tapped image?

考试:

如果我的apple.png的图像尺寸为x:1000, y:1000，并且我恰好点击了它的中心，它应该返回x: 500, y: 500

If I have apple.png by image size of x:1000, y:1000 and I tap on exactly center of it, it should return x: 500, y: 500

我需要在真实图像(UIImageView.image)上点击点像素，而不是UIImageView

I need tapped point pixels on real image (UIImageView.image) not UIImageView

推荐答案

是的，通过在图像视图中添加UITapGestureRecognizer，从中获取拍子位置并将拍子坐标转换为图像坐标:

Yes, by adding a UITapGestureRecognizer to the image view, getting the tap position from that and converting the tap coordinates to the image coordinates:

let img = UIImage(named: "whatever")

// add a tap recognizer to the image view
let tap = UITapGestureRecognizer(target: self, 
             action: #selector(self.tapGesture(_:)))
imgView.addGestureRecognizer(tap)
imgView.isUserInteractionEnabled = true
imgView.image = img
imgView.contentMode = .scaledAspectFit

func convertTapToImg(_ point: CGPoint) -> CGPoint? {
    let xRatio = imgView.frame.width / img.size.width
    let yRatio = imgView.frame.height / img.size.height
    let ratio = min(xRatio, yRatio)

    let imgWidth = img.size.width * ratio
    let imgHeight = img.size.height * ratio

    var tap = point
    var borderWidth: CGFloat = 0
    var borderHeight: CGFloat = 0
    // detect border
    if ratio == yRatio {
        // border is left and right
        borderWidth = (imgView.frame.size.width - imgWidth) / 2
        if point.x < borderWidth || point.x > borderWidth + imgWidth {
            return nil
        }
        tap.x -= borderWidth
    } else {
        // border is top and bottom
        borderHeight = (imgView.frame.size.height - imgHeight) / 2
        if point.y < borderHeight || point.y > borderHeight + imgHeight {
            return nil
        }
        tap.y -= borderHeight
    }

    let xScale = tap.x / (imgView.frame.width - 2 * borderWidth)
    let yScale = tap.y / (imgView.frame.height - 2 * borderHeight)
    let pixelX = img.size.width * xScale
    let pixelY = img.size.height * yScale
    return CGPoint(x: pixelX, y: pixelY)
}

@objc func tapGesture(_ gesture: UITapGestureRecognizer) {
    let point = gesture.location(in: imgView)
    let imgPoint = convertTapToImg(point)
    print("tap: \(point) -> img \(imgPoint)")
}

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