将MKCircle Radius转换为CoreGraphics Arc Radius [英] Convert MKCircle Radius to CoreGraphics Arc Radius

问题描述

如何将MKCircle的半径（以米为单位）转换为可用于在MKOverlayPathView子类中使用核心图形绘制圆的值？

How can I convert an MKCircle's radius (in meters) into a value I can use to draw a circle using core graphics in an MKOverlayPathView subclass?

以下代码半径硬编码为50，但我需要它来反映MKCircle的半径。

In the following code the radius is hardcoded to 50 but I need it to reflect the radius of the MKCircle.

对于位置，我使用MKMapPointForCoordinate（）将MKCircle的坐标转换为MKMapPoint ，然后使用MKOverlayPathView的pointForMapPoint：将MKMapPoint转换为一个点。但是如何将MKCircle的半径转换为相对距离？

For the position I use MKMapPointForCoordinate() to convert the MKCircle's coordinate to an MKMapPoint, then convert the MKMapPoint to a point using MKOverlayPathView's pointForMapPoint:. But how can I convert the MKCircle's radius into a relative distance?

MKCircle *circle = [self circleForLocation:location]; 
CGPoint relativePoint = [self pointForMapPoint:MKMapPointForCoordinate(circle.coordinate)];
float radius = 50;

//Fill
[self applyFillPropertiesToContext:context atZoomScale:zoomScale];
CGContextAddArc(context, relativePoint.x, relativePoint.y, radius, 0, 2*3.1415926535898, 1);
CGContextDrawPath(context, kCGPathFill);

推荐答案

MKCircle的高度和宽度 boundingMapRect 应该等于圆的直径：

The height and width of the MKCircle's boundingMapRect should be equal to the circle's diameter:

CGRect boundingRect = [self rectForMapRect:circle.boundingMapRect];
CGFloat radius = boundingRect.size.width / 2;

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