程序代码：

    Rectangle rec = new Rectangle(0,0,100, 72);//0,0坐标,长100高72的矩形
    private void button1_Click(object sender, EventArgs e)
        {
            Bitmap bmp=new Bitmap(this.Width,this.Height);//申请图片
            Graphics myGraphics = Graphics.FromImage(bmp);
            GraphicsPath myGraphicsPath = new GraphicsPath();//声明路径myGraphicsPath
            FontFamily myFontFamily = new FontFamily("黑体");
            Point myPoint = new Point(0, 0);
            StringFormat myStringFormat = new StringFormat();
            myGraphicsPath.AddString("要取交集的文字",myFontFamily, 1, 72, myPoint, myStringFormat);
            Pen myPen = new Pen(Color.Red, 1);
            myGraphics.TextRenderingHint = System.Drawing.Text.TextRenderingHint.ClearTypeGridFit;//反锯齿
            myGraphics.DrawPath(myPen, myGraphicsPath); //绘制路径myGraphicsPath
            SolidBrush myBrash = new SolidBrush(Color.Red);
            Region re = new Region(rec);//声明Region对象并用rec初始化
            re.Intersect(myGraphicsPath); //区交集
            myGraphics.FillRegion(myBrash, re); ////用myBrash填充re的内部
            this.CreateGraphics().DrawImage(bmp,0,0);//将内存中的图片显示出来
            myGraphics.Dispose();//释放资源
}