画图 利用gdi怎么画夹角

Question

c# 利用GDI+，动态给出这三个点，顶点o，上边坐标点a，下边坐标点b,，怎么画出带角度的夹角呢，如下图的样式，请帮忙给出Demo谢谢

Answer 1

要画带角度的夹角，需要使用GDI+中的绘图类Graphics和Pen来绘制直线和角度标识。

以下是C#代码示例，其中oPoint，aPoint和bPoint分别代表顶点、上边坐标点和下边坐标点：

private void DrawAngle(Point oPoint, Point aPoint, Point bPoint, Graphics graphics, Pen pen)
{
    // 计算角度
    double angle = Math.Atan2(aPoint.Y - oPoint.Y, aPoint.X - oPoint.X) - Math.Atan2(bPoint.Y - oPoint.Y, bPoint.X - oPoint.X);
    angle = angle * 180 / Math.PI;
    if (angle < 0) angle += 360;
    
    // 绘制直线
    graphics.DrawLine(pen, oPoint, aPoint);
    graphics.DrawLine(pen, oPoint, bPoint);
    
    // 绘制角度标识
    string angleText = angle.ToString("0.0") + "°";
    Font font = new Font("Arial", 10);
    SizeF textSize = graphics.MeasureString(angleText, font);
    PointF textPoint = new PointF(oPoint.X + 20, oPoint.Y - textSize.Height);
    graphics.DrawString(angleText, font, Brushes.Black, textPoint);
    
    // 绘制角度弧线
    RectangleF rect = new RectangleF(oPoint.X - 50, oPoint.Y - 50, 100, 100);
    float startAngle = (float)Math.Atan2(bPoint.Y - oPoint.Y, bPoint.X - oPoint.X) * 180 / (float)Math.PI;
    float sweepAngle = (float)angle;
    graphics.DrawArc(pen, rect, startAngle, sweepAngle);
}

在使用此方法时，需要在Paint事件中调用它，并传递Graphics对象和Pen对象，例如：

private void Form1_Paint(object sender, PaintEventArgs e)
{
    Pen pen = new Pen(Color.Black, 2);
    Point oPoint = new Point(100, 100);
    Point aPoint = new Point(200, 50);
    Point bPoint = new Point(200, 150);
    DrawAngle(oPoint, aPoint, bPoint, e.Graphics, pen);
}

这将在Form1窗体中绘制带角度标识的夹角。