C# GDI+绘制矩形圆角

一、前言

本文主要介绍C# GDI+如何绘制矩行的圆角，其中涉及到如何使用位操作来处理组合的技巧。GDI+的本质在于，它能够替代开发人员实现与显示器及其它外部设备的交互。对于控件美化而言，需要达到自己期望的效果，GDI+必不可少。绘制后的圆角效果图如下：

二、圆角枚举与相应组合处理设计

对于矩行而言，圆角分为左上角、右上角、左下角和右下角。组合情况就分为无圆角、一个圆角、二个圆角、三个圆角以及四个圆角。枚举需要满足该组合情况，没必要在枚举中将全部组合列出，只需要通过位操作就能计算出属于哪种组合。枚举类设计如下：

1    [Flags]
2     public enum RoundStyle
3     {
4         None = 0,
5         TopLeft = 1,
6         TopRight = 2,
7         BottomLeft = 4,
8         BottomRight = 8 ,
9         All = TopLeft | TopRight | BottomLeft | BottomRight
10     }

矩行的圆角所有组合情况如下：

RoundStyle.None

RoundStyle.All

RoundStyle.BottomLeft

RoundStyle.BottomRight

RoundStyle.TopLeft

RoundStyle.TopRight

对于每一种组合，必须提供相应的操作来执行路径计算，这主要是因为GraphicsPath的路径是有顺序的。因此所有组合对应的处理方式如下：

1         private static IDictionary<RoundStyle, Action<GraphicsPath, Rectangle, int, int>>
2             CreateRoundStylesEventContainer()
3         {
4             var container = new Dictionary<RoundStyle, Action<GraphicsPath, Rectangle, int, int>>();
5
6             container.Add(RoundStyle.None, (path, rect, radius, radiusAdjustment) => { path.AddRectangle(rect); });
7             container.Add(RoundStyle.All, AddAllRoundStyle);
8
9             container.Add(RoundStyle.BottomLeft, AddBottomLeftRoundStyle);
10             container.Add(RoundStyle.BottomRight, AddBottomRightRoundStyle);
11             container.Add(RoundStyle.TopLeft, AddTopLeftRoundStyle);
12             container.Add(RoundStyle.TopRight, AddTopRightRoundStyle);
13
14             container.Add(RoundStyle.BottomRight | RoundStyle.BottomLeft, AddBottomRightAndBottomLeftRoundStyle);
15             container.Add(RoundStyle.BottomRight | RoundStyle.TopRight, AddBottomRightAndTopRightRoundStyle);
16             container.Add(RoundStyle.TopRight | RoundStyle.TopLeft, AddTopRightAndTopLeftRoundStyle);
17             container.Add(RoundStyle.BottomLeft | RoundStyle.TopLeft, AddBottomLeftAndTopLeftRoundStyle);
18             container.Add(RoundStyle.BottomRight | RoundStyle.TopLeft, AddBottomRightAndTopLeftRoundStyle);
19             container.Add(RoundStyle.TopRight | RoundStyle.BottomLeft, AddTopRightAndBottomLeftRoundStyle);
20
21             container.Add(RoundStyle.BottomLeft | RoundStyle.BottomRight | RoundStyle.TopLeft, AddBottomAndTopLeftRoundStyle);
22             container.Add(RoundStyle.BottomLeft | RoundStyle.BottomRight | RoundStyle.TopRight, AddBottomAndTopRightRoundStyle);
23             container.Add(RoundStyle.BottomLeft | RoundStyle.TopLeft | RoundStyle.TopRight, AddTopAndBottomLeftRoundStyle);
24             container.Add(RoundStyle.BottomRight | RoundStyle.TopRight | RoundStyle.TopLeft, AddTopAndBottomRightRoundStyle);
25
26             return container;
27         }

三、GraphicsPath.AddArc方法

GraphicsPath.AddArc 方法如下：

1 public void AddArc(Rectangle rect, float startAngle, float sweepAngle);
2 public void AddArc(RectangleF rect, float startAngle, float sweepAngle);
3 public void AddArc(float x, float y, float width, float height, float startAngle, float sweepAngle);
4 public void AddArc(int x, int y, int width, int height, float startAngle, float sweepAngle);

此方法主要是绘制圆角的，绘制的方式与二位坐标的角度是不一样，官方参数资料如下：

x                 矩形区域左上角的 X 轴坐标，这个矩形区域定义用來绘制弧形的橢圆形。
y                 矩形区域左上角的 Y 轴座標，这个矩形区域定义用來绘制弧形的橢圆形。
width           矩形区域的寬度，这个矩形区域定义用來绘制弧形的橢圆形。
height          矩形区域的高度，这个矩形区域定义用來绘制弧形的橢圆形。
startAngle   弧形的开始点角度，順時针自 X 轴所测得的度数。
sweepAngle 介於弧形的 startAngle 和结束点的角度。

如果圆形中具有先前的直线或曲线，会加入线段來将先前线段的结束点连接到弧形的开端。
弧形是沿着指定矩形范围內的橢圆形周围所描绘的。弧形的开始点是由橢圆形的 X 轴 (0 度角) 順時针测量开始点角度的度数所決定。结束点位置的決定很类似，从开始点順時针测量跨越角度的度数所決定。如果跨越的角度大於 360 度或小於 -360 度，则弧形分別跨越了 360 度或 -360 度。

弧形的开始点是由橢圆形的 X 轴 (0 度角) 順時针测量开始点角度的度数所決定,GraphicsPath增加对象的顺序也是需要注意的（有部分连接线是系统绘制的）。此处与数学中二位坐标定义的角度是反方向的，需要特别注意。

四、绘制圆角组合

3.1 绘制一个圆角

矩行的一个圆角所有组合情况如下：RoundStyle.BottomLeft、RoundStyle.BottomRight、RoundStyle.TopLeft、RoundStyle.TopRight。绘制方法如下：

绘制一个圆角

        private static void AddBottomLeftRoundStyle(GraphicsPath path,
            Rectangle rect, int radius, int radiusAdjustment)
        {
            AddBottomLeftArc(rect, radius, path, radiusAdjustment);
            AddTopLine(rect, path, radiusAdjustment);
            AddRightLine(rect, path, radiusAdjustment);
        }

        private static void AddBottomRightRoundStyle(GraphicsPath path,
            Rectangle rect, int radius, int radiusAdjustment)
        {
            AddBottomRightArc(rect, radius, path, radiusAdjustment);
            AddLeftLine(rect, path, radiusAdjustment);
            AddTopLine(rect, path, radiusAdjustment);
        }

        private static void AddTopRightRoundStyle(GraphicsPath path,
            Rectangle rect, int radius, int radiusAdjustment)
        {
            AddTopRightArc(rect, radius, path, radiusAdjustment);
            AddBottomLine(rect, path, radiusAdjustment);
            AddLeftLine(rect, path, radiusAdjustment);
        }

        private static void AddTopLeftRoundStyle(GraphicsPath path,
            Rectangle rect, int radius, int radiusAdjustment)
        {
            AddTopLeftArc(rect, radius, path, radiusAdjustment);
            AddRightLine(rect, path, radiusAdjustment);
            AddBottomLine(rect, path, radiusAdjustment);
        }

效果图如下：

3.2 绘制二个圆角

矩行的一个圆角所有组合情况如下：

绘制方法如下：

绘制二个圆角

        private static void AddTopRightAndBottomLeftRoundStyle(GraphicsPath path,
            Rectangle rect, int radius, int radiusAdjustment)
        {
            AddTopRightArc(rect, radius, path, radiusAdjustment);
            AddBottomLineWithLeftOffset(path, rect, radius, radiusAdjustment, false);
            AddBottomLeftArc(rect, radius, path, radiusAdjustment);
            AddTopLineWithRightOffset(path, rect, radius, radiusAdjustment);
        }

        private static void AddBottomRightAndTopLeftRoundStyle(GraphicsPath path,
            Rectangle rect, int radius, int radiusAdjustment)
        {
            AddBottomRightArc(rect, radius, path, radiusAdjustment);
            AddBottomLineWithRightOffset(path, rect, radius, radiusAdjustment);
            AddTopLeftArc(rect, radius, path, radiusAdjustment);
            AddTopLineWithLeftOffset(path, rect, radius, radiusAdjustment);
        }

        private static void AddBottomLeftAndTopLeftRoundStyle(GraphicsPath path,
            Rectangle rect, int radius, int radiusAdjustment)
        {
            AddBottomLeftArc(rect, radius, path, radiusAdjustment);
            AddTopLeftArc(rect, radius, path, radiusAdjustment);
            AddRightLine(rect, path, radiusAdjustment);
        }

        private static void AddTopRightAndTopLeftRoundStyle(GraphicsPath path,
            Rectangle rect, int radius, int radiusAdjustment)
        {
            AddTopLeftArc(rect, radius, path, radiusAdjustment);
            AddTopRightArc(rect, radius, path, radiusAdjustment);
            AddBottomLine(rect, path, radiusAdjustment);
        }

        private static void AddBottomRightAndTopRightRoundStyle(GraphicsPath path,
            Rectangle rect, int radius, int radiusAdjustment)
        {
            AddTopRightArc(rect, radius, path, radiusAdjustment);
            AddBottomRightArc(rect, radius, path, radiusAdjustment);
            AddLeftLine(rect, path, radiusAdjustment);
        }

        private static void AddBottomRightAndBottomLeftRoundStyle(GraphicsPath path,
            Rectangle rect, int radius, int radiusAdjustment)
        {
            AddBottomRightArc(rect, radius, path, radiusAdjustment);
            AddBottomLeftArc(rect, radius, path, radiusAdjustment);
            AddTopLine(rect, path, radiusAdjustment);
        }

效果图如下：

3.2 绘制三个圆角

矩行的一个圆角所有组合情况如下：

绘制方法如下：

绘制三个圆角

        private static void AddTopAndBottomRightRoundStyle(GraphicsPath path,
            Rectangle rect, int radius, int radiusAdjustment)
        {
            AddTopLeftArc(rect, radius, path, radiusAdjustment);
            AddTopRightArc(rect, radius, path, radiusAdjustment);
            AddBottomRightArc(rect, radius, path, radiusAdjustment);
            AddBottomLineWithRightOffset(path, rect, radius, radiusAdjustment);
        }

        private static void AddTopAndBottomLeftRoundStyle(GraphicsPath path,
            Rectangle rect, int radius, int radiusAdjustment)
        {
            AddTopLeftArc(rect, radius, path, radiusAdjustment);
            AddTopRightArc(rect, radius, path, radiusAdjustment);
            AddBottomLineWithLeftOffset(path, rect, radius, radiusAdjustment, false);
            AddBottomLeftArc(rect, radius, path, radiusAdjustment);
        }

        private static void AddBottomAndTopRightRoundStyle(GraphicsPath path,
            Rectangle rect, int radius, int radiusAdjustment)
        {
            AddBottomRightArc(rect, radius, path, radiusAdjustment);
            AddBottomLeftArc(rect, radius, path, radiusAdjustment);
            AddTopLineWithRightOffset(path, rect, radius, radiusAdjustment);
            AddTopRightArc(rect, radius, path, radiusAdjustment);
        }

        private static void AddBottomAndTopLeftRoundStyle(GraphicsPath path,
            Rectangle rect, int radius, int radiusAdjustment)
        {
            AddBottomRightArc(rect, radius, path, radiusAdjustment);
            AddBottomLeftArc(rect, radius, path, radiusAdjustment);
            AddTopLeftArc(rect, radius, path, radiusAdjustment);
            AddTopLineWithLeftOffset(path, rect, radius, radiusAdjustment);
        }

效果图如下：

3.4 绘制四个圆角

矩行的四个圆角所有组合情况如下：RoundStyle.All或者RoundStyle.BottomLeft | RoundStyle.BottomRight | RoundStyle.TopLeft | RoundStyle.TopRight。

绘制方法如下：

绘制四个圆角

        private static void AddAllRoundStyle(GraphicsPath path,
            Rectangle rect, int radius, int radiusAdjustment)
        {
            AddTopLeftArc(rect, radius, path, radiusAdjustment);
            AddTopRightArc(rect, radius, path, radiusAdjustment);
            AddBottomRightArc(rect, radius, path, radiusAdjustment);
            AddBottomLeftArc(rect, radius, path, radiusAdjustment);
        }

效果图如下：

四、总结

绘制圆角在美化控件方面的场景还是比较多的，本文采用枚举的位操作来对所有情况进行操作。有一段时间没写随笔了，可以写的东西很多，由于个人的时间问题却一直拖到现在。上面的圆角绘制例子是昨天作为练习写的，只是简单的手动测试了一下，如有BUG请及时通知本人，不胜感激。目前开发的产品很多控件都需要自绘，统计学需要写的算法也比较多。虽然项目成员总人数为100，但开发所占的比例才40%不到，任重而道远。

源码下载：矩阵圆角绘制源码

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原文地址：https://www.cnblogs.com/jasenkin/p/draw_rectangle_round.html