Question

我想实现一个简单的程序，使用UIPanGestureRecognizer显示手指在图像上的点的颜色。但是，从gesture.location（in :)函数返回的CGPoint的x和y值大于预期值，因此图像中选定的颜色不正确。

例如，imageView.frame.size.width打印为375.但是当您拖动到屏幕右侧时，平移手势的x位置的最大返回值为413。

为什么返回的CGPoint的x和y值大于UIImageView的边界？

class ViewController: UIViewController {

@IBOutlet weak var imageView: UIImageView!
var squareView: UIView!
var imgheight: CGFloat!
var imgwidth: CGFloat!
var heightDif: CGFloat!

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.
    squareView = UIView(frame: CGRect(x: 0, y: 0, width: 100, height: 100))
    squareView.backgroundColor = getPixelColor(pos: CGPoint(x: 50, y: 50))
    view.addSubview(squareView)

    imgheight = imageView.image?.size.height
    imgwidth = imageView.image?.size.width
    heightDif = (imageView.frame.size.height - imgheight)/2

    let panGesture = UIPanGestureRecognizer(target: self, action: #selector(handlePan(recognizer:)))
    imageView.addGestureRecognizer(panGesture)
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

func getPixelColor(pos: CGPoint) -> UIColor {

    let pixelData = imageView.image?.cgImage!.dataProvider!.data
    let data: UnsafePointer<UInt8> = CFDataGetBytePtr(pixelData)

    let pixelInfo: Int = ((Int(imageView.image!.size.width) * Int(pos.y)) + Int(pos.x)) * 4

    let r = CGFloat(data[pixelInfo]) / CGFloat(255.0)
    let g = CGFloat(data[pixelInfo+1]) / CGFloat(255.0)
    let b = CGFloat(data[pixelInfo+2]) / CGFloat(255.0)
    let a = CGFloat(data[pixelInfo+3]) / CGFloat(255.0)

    return UIColor(red: r, green: g, blue: b, alpha: a)
}

@objc func handlePan(recognizer: UIPanGestureRecognizer) {
    var point = recognizer.location(in: self.imageView)
    point.y -= heightDif
    if point.x >= 0 && point.y >= 0 {
        squareView.backgroundColor = getPixelColor(pos: point)
    }

}
}

感谢您的帮助！

Answer 1

我通过以编程方式创建imageView而不是使用故事板来修复此问题。这让我可以精确控制imageView的参数，识别器。位置函数返回了预期的结果。

var imageView: UIImageView!

然后，我在viewDidLoad（）中声明了它的界限：

frame = CGRect(x: 0, y: 0, width: image.size.wdith, height: image.size.height)
imageView = UIImageView(frame: frame)
view.addSubview(imageView)

其余的代码是一样的，一切正常！

为什么recognizer.location（in :)返回比视图边界更大的x和y值？

1 个答案: