自定义控件实现图像的显示和放大缩小，平移，右击菜单选择“自适应窗口”“保存图像”

前面介绍了2个控件组合在一起实现，对PictureBox控件的操作，今天我们自己新建一个控件来自己用。

新建一个Windows窗体解决方案，添加“用户控件”，把PictureBox控件拖到指定的区域，给我们要自己定义的控件改下名字UserControl_Display

界面就完成了，现在我们要自定义的控件添加事件和右击菜单（contextMenuStrip1）控件

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Drawing;
using System.Data;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace _自定义控件显示图片
{
    public partial class UserControl_Display : UserControl
    {

        public System.Drawing.Point mouseDownPoint;//存储鼠标焦点的全局变量
        public bool isSelected = false;
        public int width;
        public int height;
     

        public UserControl_Display()
        {
            InitializeComponent();
        }

        //这个是显示图片用的
        public  void Display(Image  image)
        {
            pictureBox1.Image = image;

            width = pictureBox1.Width;//控件的原始大小保存一下，恢复的时候用
            height = pictureBox1.Height;      
        }

         // 在MouseUp处获知鼠标是否松开，终止拖动操作；
        private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
        {
            isSelected = false;
        }

        private void pictureBox1_MouseEnter(object sender, EventArgs e)
        {
            pictureBox1.Focus();
            pictureBox1.Cursor = Cursors.SizeAll;
        }

        //在MouseDown处获知鼠标是否按下，并记录下此时的鼠标坐标值；
        private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left)
            {
                mouseDownPoint.X = Cursor.Position.X;  //注：全局变量mouseDownPoint前面已定义为Point类型  
                mouseDownPoint.Y = Cursor.Position.Y;
                isSelected = true;
            }

        }

        //图片平移,在MouseMove处添加拖动函数操作
        private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
        {
            if (isSelected && IsMouseInPanel())//确定已经激发MouseDown事件，和鼠标在picturebox的范围内
            {
                this.pictureBox1.Left = this.pictureBox1.Left + (Cursor.Position.X - mouseDownPoint.X);
                this.pictureBox1.Top = this.pictureBox1.Top + (Cursor.Position.Y - mouseDownPoint.Y);
                mouseDownPoint.X = Cursor.Position.X;
                mouseDownPoint.Y = Cursor.Position.Y;
            }
        }

        private void pictureBox1_MouseWheel(object sender, MouseEventArgs e)
        {
            double scale = 1;
            if (pictureBox1.Height > 0)
            {
                scale = (double)pictureBox1.Width / (double)pictureBox1.Height;
            }
            pictureBox1.Width += (int)(e.Delta * scale);
            pictureBox1.Height += e.Delta;
        }


        private bool IsMouseInPanel()
        {
            if (this.pictureBox1.Left < PointToClient(Cursor.Position).X
                    && PointToClient(Cursor.Position).X < this.pictureBox1.Left
                    + this.pictureBox1.Width && this.pictureBox1.Top
                    < PointToClient(Cursor.Position).Y && PointToClient(Cursor.Position).Y
                    < this.pictureBox1.Top + this.pictureBox1.Height)
            {
                return true;
            }
            else
            {
                return false;
            }

        }


        /// <summary>
        /// 右击菜单的保存图像
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void SaveImage_Click(object sender, EventArgs e)
        {
            Image image = this.pictureBox1.Image;
            string imageName = DateTime.Now.ToString("HH时MM分SS秒") + ".bmp";
            image.Save(@imageName);
        }

        //右击菜单的图像适应控件的大小
        private void ImageFitPictureBox_Click(object sender, EventArgs e)
        { 
            pictureBox1.Width = width;//控件的大小恢复
            pictureBox1.Height = height;

            //PictureBox控件的位置
            pictureBox1.Left = 1;
            pictureBox1.Top = 1;       
        }
    }
}