多个 CGAffineTransform 语句不会给出平滑的结果

Question

我正在我的 UIView 上应用旋转和缩放。 当我应用这些变换中的一个时，它工作正常但是当我尝试同时应用这两个时，结果有点不太顺利。它显示为重置并开始应用。这是我的代码在此处输入代码

var location:CGPoint = CGPoint.zero
var rotatingLoaction:CGPoint = CGPoint.zero
var deltaAngle: CGFloat!
func handleRotateAndResizeWithPanGestureRecognizer(_ recognizer: UIPanGestureRecognizer) -> Void
{
    location = recognizer.location(in: self.superview)

    let sizeCenter = CGPoint(x: (self.frame.origin.x + self.frame.size.width) / 2.0, y: (self.frame.origin.y + self.frame.size.height) / 2.0)

    if recognizer.state == .began {
        initialDistance = sizeCenter.getDistance(point: location)
        deltaAngle = atan2(location.y - sizeCenter.y, location.x - sizeCenter.x) - self.transform.getAngle()
    }
    else if recognizer.state == .changed
    {
        let ang = atan2(location.y - sizeCenter.y,
                          location.x - sizeCenter.x);
        let angleDiff = deltaAngle - ang;

        self.setNeedsDisplay()
        var t = CGAffineTransform.identity
        let distance = CGFloat(sizeCenter.getDistance(point: location))
        let scale =  distance / initialDistance
        t = t.rotated(by: -angleDiff)
        t = t.scaledBy(x:  CGFloat(scale), y: CGFloat(scale))

        self.transform  =  t

        self.setNeedsDisplay()
         print("\(center )    \(scale)")
    }

}

更新这是我的getDistance方法，它是用CGPoint的扩展写的

func getDistance(point: CGPoint) -> CGFloat {
        let fx = (point.x - self.x);
        let fy = (point.y - self.y);

        return sqrt((fx*fx + fy*fy))
    }

Answer 1

看起来角度按预期工作，但不是缩放。我可以看到，每次开始拖动时，都会考虑当前的视角，但不会考虑当前的缩放比例。所以答案在于每次开始拖动时相对于其先前状态缩放视图。

如果没有运行示例，我无法对此进行测试，但我认为，如果您进行这个小改动，您可能会得到想要的结果：

if recognizer.state == .began {
    initialDistance = sizeCenter.getDistance(point: location) / sqrt(transform.a * transform.a + transform.c * transform.c)

多个 CGAffineTransform 语句不会给出平滑的结果

Multiple CGAffineTranform statements dont give smooth results

ios

iphone

swift

cgaffinetransform

cgaffinetransformscale