C#-如何获取System.Drawing.Region的区域? [英] C# - How to get the area of a System.Drawing.Region?

问题描述

在排除一些圆的面积之后，我正在计算矩形的面积.这是我目前的解决方案:

I'm computing the area of a rectagle after exclude the area of some circles. this is my current solution:

    var region = new Region( new Rectangle(0, 0, 10, 10) );
    var circle = new System.Drawing.Drawing2D.GraphicsPath();
    circle.AddEllipse(50, 50, 25, 25);
    // Exclude the circle from the region.
    region.Exclude(circle);

但是我需要诸如region.getArea()之类的东西才能在排除圆后获取面积.

However I need something like region.getArea() to get the area after excluding the circle.

您知道如何计算System.Drawing.Region区域吗?

-或-

在排除某些圆之后，您知道另一种计算矩形面积的方法吗?

推荐答案

        float diam = 25;
        var region = new Region(new RectangleF(0, 0, diam, diam));
        var circle = new System.Drawing.Drawing2D.GraphicsPath();
        circle.AddEllipse(0, 0, diam, diam);
        region.Exclude(circle);

        var rects = region.GetRegionScans(new System.Drawing.Drawing2D.Matrix());
        float area = 0;
        foreach (var rc in rects) area += rc.Width * rc.Height;
        double realArea = diam * diam - Math.PI * diam * diam / 4;
        Console.WriteLine("Approx area = {0}, real area = {1}", area, realArea);

输出:大约面积= 141，实际面积= 134.126147876595

Output: Approx area = 141, real area = 134.126147876595

请记住此结果，Region类旨在用于图形代码.它仅对具有诀窍的像素准确，以便累积舍入误差. diam 越大，相对误差越小.

Keep this result in mind, the Region class was designed to be used in graphic code. It is only accurate to a pixel with a knack for rounding errors to accumulate. The larger you make diam, the smaller the relative error.

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