ios - 计算addCurveToPoint控制点

Question

我正在使用CoreGraphics绘制一个圆角矩形，我熟悉可以绘制该圆角矩形的CG API，但是我不想使用它，因为该矩形不是一个完全均匀的圆角矩形，其中一部分是一个圆角矩形，其他部分将是一组连接的路径，例如，左上角和右上角将是一个圆角矩形边缘，但是，底部边缘是一组连接的贝塞尔曲线路径。

我的问题是，如果要绘制整个形状作为Bezier路径，应如何在addCurveToPoint中计算拐角的控制点？我知道点的半径和坐标(也基于半径)。

(更新)

I have a sample code, I am trying to understand the math behind it:

UIBezierPath * rectangle = [UIBezierPath bezierPath];
[rectangle moveToPoint:CGPointMake(0, 8)];
[rectangle addCurveToPoint:CGPointMake(8.01, 0) controlPoint1:CGPointMake(0, 3.58) controlPoint2:CGPointMake(3.59, 0)];
[rectangle addLineToPoint:CGPointMake(208, 0)];
[rectangle addCurveToPoint:CGPointMake(224, 16.01) controlPoint1:CGPointMake(216.84, 0) controlPoint2:CGPointMake(224, 7.16)];
[rectangle addLineToPoint:CGPointMake(224, 175)];
[rectangle addCurveToPoint:CGPointMake(192, 207) controlPoint1:CGPointMake(224, 192.67) controlPoint2:CGPointMake(209.67, 207)];
[rectangle addLineToPoint:CGPointMake(64, 207)];
[rectangle addCurveToPoint:CGPointMake(0, 142.99) controlPoint1:CGPointMake(28.65, 207) controlPoint2:CGPointMake(0, 178.35)];
[rectangle addLineToPoint:CGPointMake(0, 8)];
[rectangle closePath];

左上角，右上角，右下角和左下角的拐角半径分别为8、16、32和64

谢谢

Answer 1

我假设您想为圆角添加一个90度弧线。使用addArc而不是addCurveToPoint。

在Swift 3中

var path = UIBezierPath()

...

let center = CGPoint(x: topLeft.x + width - radius, y: topLeft.y)
path.addArc(withCenter: center, radius: radius, startAngle: CGFloat.pi, endAngle: CGFloat.pi * CGFloat(1.5), clockwise: true)

当然，您的参数会有所不同。

更新

根据您的代码，它应如下所示:

UIBezierPath * rectangle = [UIBezierPath bezierPath];
[rectangle moveToPoint:CGPointMake(0, 8)];
[rectangle addArcWithCenter:CGPointMake(8, 8) radius:8 startAngle:M_PI endAngle:M_PI*1.5 clockwise:YES];
[rectangle addLineToPoint:CGPointMake(208, 0)];
[rectangle addArcWithCenter:CGPointMake(208, 16) radius:16 startAngle:M_PI*1.5 endAngle:0 clockwise:YES];
[rectangle addLineToPoint:CGPointMake(224, 175)];
[rectangle addArcWithCenter:CGPointMake(208, 175) radius:32 startAngle:0 endAngle:M_PI*0.5 clockwise:YES];
[rectangle addLineToPoint:CGPointMake(64, 207)];
[rectangle addArcWithCenter:CGPointMake(64, 175) radius:64 startAngle:M_PI*0.5 endAngle:M_PI clockwise:YES];
[rectangle closePath];