将箭头附加到 UIBezierPath [英] append arrowhead to UIBezierPath

问题描述

我需要你的帮助:

我正在尝试使用具有可变宽度的 UIBezierPaths 创建一个图形，该图形由带有两个控制点的贝塞尔曲线组成.现在我想在这些路径的末端(右侧)添加箭头.有没有办法做到这一点，即通过附加一个包含三角形的较小 lineWidth 的子路径?这是我想添加箭头的一些路径的示例图片:

I am trying to create a graph using UIBezierPaths with variable widths and consisting of a bezier curve with two control points. Now I'd like to add arrow heads to the end (right hand side) of these paths. Is there a way to do this i.e. by appending a subpath with a smaller lineWidth which contains a triangle? here is a sample picture of some paths to which I'd like to add arrowheads:

感谢您的帮助！

推荐答案

假设你画了一个这样的弧线:

Let's assume you drew one of arcs like so:

UIBezierPath *path = [UIBezierPath bezierPath];

[path moveToPoint:point1];
[path addQuadCurveToPoint:point3 controlPoint:point2];

CAShapeLayer *shape = [CAShapeLayer layer];
shape.path = path.CGPath;
shape.lineWidth = 10;
shape.strokeColor = [UIColor blueColor].CGColor;
shape.fillColor = [UIColor clearColor].CGColor;
shape.frame = self.view.bounds;
[self.view.layer addSublayer:shape];

可以使用atan2来计算控制点到终点的角度:

You can use atan2 to calculate the angle from the control point to the final point:

CGFloat angle = atan2f(point3.y - point2.y, point3.x - point2.x);

请注意，使用四边形贝塞尔曲线还是三次方并不重要，想法是一样的.计算最后一个控制点到终点的角度.

Note, it doesn't really matter if you use quad bezier or cubic, the idea is the same. Calculate the angle from the last control point to the end point.

然后你可以通过计算三角形的角来放置一个箭头，如下所示:

You could then put an arrow head by calculating the corners of the triangle like so:

CGFloat distance = 15.0;
path = [UIBezierPath bezierPath];
[path moveToPoint:point3];
[path addLineToPoint:[self calculatePointFromPoint:point3 angle:angle + M_PI_2 distance:distance]]; // to the right
[path addLineToPoint:[self calculatePointFromPoint:point3 angle:angle          distance:distance]]; // straight ahead
[path addLineToPoint:[self calculatePointFromPoint:point3 angle:angle - M_PI_2 distance:distance]]; // to the left
[path closePath];

shape = [CAShapeLayer layer];
shape.path = path.CGPath;
shape.lineWidth = 2;
shape.strokeColor = [UIColor blueColor].CGColor;
shape.fillColor = [UIColor blueColor].CGColor;
shape.frame = self.view.bounds;
[self.view.layer addSublayer:shape];

我们使用 sinf 和 cosf 像这样计算角点:

Where we use sinf and cosf to calculate the corners like so:

- (CGPoint)calculatePointFromPoint:(CGPoint)point angle:(CGFloat)angle distance:(CGFloat)distance {
    return CGPointMake(point.x + cosf(angle) * distance, point.y + sinf(angle) * distance);
}

结果如下:

显然，只需调整distance参数即可控制三角形的形状.

Clearly, just adjust the distance parameters to control the shape of the triangle.

这篇关于将箭头附加到 UIBezierPath的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！