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
RoundStyle.BottomRight | RoundStyle.BottomLeft
RoundStyle.BottomRight | RoundStyle.TopRightRoundStyle.TopRight | RoundStyle.TopLeftRoundStyle.BottomLeft | RoundStyle.TopLeftRoundStyle.BottomRight | RoundStyle.TopLeftRoundStyle.TopRight | RoundStyle.BottomLeftRoundStyle.BottomLeft | RoundStyle.BottomRight | RoundStyle.TopLeft
RoundStyle.BottomLeft | RoundStyle.BottomRight | RoundStyle.TopRightRoundStyle.BottomLeft | RoundStyle.TopLeft | RoundStyle.TopRightRoundStyle.BottomRight | RoundStyle.TopRight | RoundStyle.TopLeft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：
RoundStyle.BottomRight | RoundStyle.BottomLeft
RoundStyle.BottomRight | RoundStyle.TopRightRoundStyle.TopRight | RoundStyle.TopLeftRoundStyle.BottomLeft | RoundStyle.TopLeftRoundStyle.BottomRight | RoundStyle.TopLeftRoundStyle.TopRight | RoundStyle.BottomLeft。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：
RoundStyle.BottomLeft | RoundStyle.BottomRight | RoundStyle.TopLeft
RoundStyle.BottomLeft | RoundStyle.BottomRight | RoundStyle.TopRightRoundStyle.BottomLeft | RoundStyle.TopLeft | RoundStyle.TopRightRoundStyle.BottomRight | RoundStyle.TopRight | RoundStyle.TopLeft。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：