从另一个路径的线宽轮廓生成CGPath

问题描述

我可能不会以最好的方式来解释这一点，所以请您忍受。

I might not be explaining this in the best way possible, so please bear with me.

我所拥有的是在MKMapView对象顶部绘制的CGPath：

What I have is a drawn CGPath on top of a MKMapView object:

我能够实现此目的的方法是为较深的蓝线创建CGPath，然后创建该路径的副本，然后使用半透明的蓝色描出该路径的较粗版本。这是我目前正在使用的代码：

The way I was able to achieve this is to create a CGPath for the darker blue line, then create a copy of that path, and then stroke a thicker version of it with a semi-transparent blue color. Here's the code that I'm currently using for this:

    // set the shadow around the path line
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextSaveGState(context);
    CGContextSetRGBStrokeColor(context, 0.0f, 0.0f, 0.0f, 0.0f);
    CGContextSetRGBFillColor(context, 0.0f, 0.0f, 1.0f, 0.4f);
    CGPathRef shadowPath = CGPathCreateCopyByStrokingPath(self.path.CGPath, NULL, 80.0f, kCGLineCapRound, kCGLineJoinRound, 0.0f);
    CGContextBeginPath(context);
    CGContextAddPath(context, shadowPath);
    CGContextDrawPath(context, kCGPathFillStroke);
    CGContextRestoreGState(context);
    CGPathRelease(shadowPath);

效果很好，到目前为止没有错。

Works pretty well, nothing wrong so far.

但是，我想做的是获取一个较粗的半透明蓝色区域的轮廓的CGPathRef。这是另一个截图，显示了我想要的伪路径（用红色绘制）：

However, what I would like to do though is to get a CGPathRef of the outline of that thicker semi-transparent blue area. Here's another screenshot showing the pseudo-path that I want out of this (hand drawn in red):

这怎么可能？

推荐答案

简单：只需使用。传递宽线宽，并且上限为 kCGLineCapRound 。

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