Image 鼠标拖拽与鼠标中键的缩放

一、Image在窗体上拖拽，势必会用到鼠标的三个事件(MouseDown，MouseUp，MouseMove)，以左键为例，PictureBox为载体

        Point mouseDownPoint = new Point(); //记录拖拽过程鼠标位置
        bool isMove = false;    //判断鼠标在picturebox上移动时，是否处于拖拽过程(鼠标左键是否按下)
       private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left)
            {
                mouseDownPoint.X = Cursor.Position.X;
                mouseDownPoint.Y = Cursor.Position.Y;
                isMove = true;
            }
        }
        private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
        {
            pictureBox1.Dock = DockStyle.None;
            if (e.Button == MouseButtons.Left)
            {
                isMove = false;
            }
        }

        private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
        {
            
            if (isMove)
            {
                int x, y;
                int moveX, moveY;
                moveX = Cursor.Position.X - mouseDownPoint.X;
                moveY = Cursor.Position.Y - mouseDownPoint.Y;
                x = pictureBox1.Location.X + moveX;
                y = pictureBox1.Location.Y + moveY;
                pictureBox1.Location = new Point(x, y);
                mouseDownPoint.X = Cursor.Position.X;
                mouseDownPoint.Y = Cursor.Position.Y;
            }
        }

二、(1)鼠标滚轮------Image缩放(实现思路，靠设置PictureBox里SizeModel属性为Zoom,改变PictureBox大小进行放缩，大图片有卡顿，慢等问题，后续优化)

         Bitmap myBmp;
         int zoomStep = 40;      //缩放步长
        //窗体加载事件
        private void Form_Load(object sender, EventArgs e)
        {
             string filename = "图片路径+文件名(包括扩展名)"
             myBmp = new Bitmap(filename);//多种重载，基于自己的方式，将Image赋值与画布
             pictureBox1.Image = myBmp;
             pictureBox1.SizeMode = PictureBoxSizeMode.Zoom; //设置picturebox为缩放模式
         }
       //PictureBox控件绑定上鼠标中键事件
       private void pictureBox1_MouseWheel(object sender, MouseEventArgs e)
        {
            int x = e.Location.X;
            int y = e.Location.Y;
            int ow = pictureBox1.Width;
            int oh = pictureBox1.Height;
            int VX, VY;
            if (e.Delta > 0)
            {
                pictureBox1.Width += zoomStep;
                pictureBox1.Height += zoomStep;

                PropertyInfo pInfo = pictureBox1.GetType().GetProperty("ImageRectangle", BindingFlags.Instance |
                                                                                         BindingFlags.NonPublic);
                Rectangle rect = (Rectangle)pInfo.GetValue(pictureBox1, null);

                pictureBox1.Width = rect.Width;
                pictureBox1.Height = rect.Height;
            }
            if (e.Delta < 0)
            {

                if (pictureBox1.Width < myBmp.Width / 10)
                    return;

                pictureBox1.Width -= zoomStep;
                pictureBox1.Height -= zoomStep;
                PropertyInfo pInfo = pictureBox1.GetType().GetProperty("ImageRectangle", BindingFlags.Instance |
                                                                                         BindingFlags.NonPublic);
                Rectangle rect = (Rectangle)pInfo.GetValue(pictureBox1, null);
                pictureBox1.Width = rect.Width;
                pictureBox1.Height = rect.Height;
            }

            VX = (int)((double)x * (ow - pictureBox1.Width) / ow);
            VY = (int)((double)y * (oh - pictureBox1.Height) / oh);
            pictureBox1.Location = new Point(pictureBox1.Location.X + VX, pictureBox1.Location.Y + VY);
        }