用c#写画图形

 

La Code

Time to code. In the following, I describe briefly the steps in which I developed this button.

Step 1

Simple round button. Visuals done. Behaviorally similar to a rectangular button. We create one pen and one brush. The pen, to draw the boundary ellipse/ circle; the brush: to fill interior of the ellipse.

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constructor:
{
      _pen = new Pen(_color);
      _brush = new SolidBrush(Color.FromKnownColor (KnownColor.Control));
      _brushInside = new SolidBrush(_color);
}

// OnPaint…
protected override void OnPaint(PaintEventArgs pe)
{
      Graphics g = pe.Graphics;//创建图形对象
      g.FillRectangle(_brush, 0, 0, ClientSize.Width, ClientSize.Height);//用brush填充矩形
      g.DrawEllipse(_pen, 0, 0, ClientSize.Width, ClientSize.Height);//画椭圆
      g.FillEllipse(_brushInside, 0, 0, ClientSize.Width, ClientSize.Height);
}

Additionally, you want to expose a color property that the end user can populate in design mode.

Step 2

The implementation in Step 1 has a bug: if you click at a point which lies outside the bounding circle but inside the bounding rectangle, that gets interpreted as a click.

To fix that, we add the following code in OnPaint to set the window region correctly:

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      GraphicsPath path = new GraphicsPath();
      path.AddEllipse(0, 0, ClientSize.Width, ClientSize.Height);
      this.Region = new Region(path);

Step 3