C#之在PictureBox上绘制动态矩形框

C#之在PictureBox上绘制动态矩形框

多次做项目都用到了画ROI区域，简单来说就是在PictureBox上画矩形区域，特写此博文以方便日后查阅。

在PictureBox上画矩形主要利用了以下几个事件：

1、MouseDown事件

        Point start;  //起始点
        Point end;   //结束点
        bool blnDraw;   //在MouseMove事件中判断是否绘制矩形框
        private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left)
            {
                start = e.Location;
                blnDraw = true;
            }
        }

2、MouseMove事件

        private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
        {
            if (blnDraw)
            {
                if (e.Button != MouseButtons.Left) return;
                end = e.Location;
                pictureBox1.Invalidate();//此代码不可省略
            }

        }

3、MouseUp事件

        private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left)
            {
                endPoint = e.Location;
                blnDraw = false;
            }
        }

4、Paint事件

        private void pictureBox1_Paint(object sender, PaintEventArgs e)
        {
            PictureBox pic = sender as PictureBox;
            Pen pen = new Pen(Color.Red, 3);
            pen.DashStyle = System.Drawing.Drawing2D.DashStyle.Dot;     //绘制线的格式
            if (blnDraw)
            {
                //此处是为了在绘制时可以由上向下绘制，也可以由下向上
                e.Graphics.DrawRectangle(pen, Math.Min(start.X, end.X), Math.Min(start.Y, end.Y), Math.Abs(start.X - end.X), Math.Abs(start.Y - end.Y));
            }
            pen.Dispose();
        }

效果：