实现winform下的简单截图

1.调用截图窗体的代码：

[code]Bitmap CatchBmp = new Bitmap(Screen.AllScreens[0].Bounds.Width, Screen.AllScreens[0].Bounds.Height);//新建一个和屏幕大小相同的图片　　　　
  System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(CatchBmp);
  g.CopyFromScreen(new Point(0, 0), new Point(0, 0), new Size(Screen.AllScreens[0].Bounds.Width, Screen.AllScreens[0].Bounds.Height));//保存全屏图片

  snapscreen screen = new snapscreen();
  screen.BackgroundImage = CatchBmp;
  screen.ShowDialog();

  panel1.BackgroundImage = Clipboard.GetImage();
  globalBitMap = panel1.BackgroundImage.Clone() as Bitmap;//保存副本

2.截屏弹出窗体的designer文件代码(vs生成的)：

[code]namespace Graphics
{
    partial class snapscreen
    {
        /// <summary>
        /// Required designer variable.
        /// </summary>
        private System.ComponentModel.IContainer components = null;

        /// <summary>
        /// Clean up any resources being used.
        /// </summary>
        /// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
        protected override void Dispose(bool disposing)
        {
            if (disposing && (components != null))
            {
                components.Dispose();
            }
            base.Dispose(disposing);
        }

        #region Windows Form Designer generated code

        /// <summary>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
        private void InitializeComponent()
        {
            this.SuspendLayout();
            // 
            // snapscreen
            // 
            this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 12F);
            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
            this.ClientSize = new System.Drawing.Size(394, 372);
            this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.None;
            this.Location = new System.Drawing.Point(1000, 600);
            this.Name = "snapscreen";
            this.StartPosition = System.Windows.Forms.FormStartPosition.Manual;
            this.Text = "snapscreen";
            this.WindowState = System.Windows.Forms.FormWindowState.Maximized;
            this.Load += new System.EventHandler(this.snapscreen_Load); 
            this.KeyDown += new System.Windows.Forms.KeyEventHandler(this.snapscreen_KeyDown);
            this.MouseDoubleClick += new System.Windows.Forms.MouseEventHandler(this.snapscreen_MouseDoubleClick);
            this.MouseDown += new System.Windows.Forms.MouseEventHandler(this.snapscreen_MouseDown);
            this.MouseMove += new System.Windows.Forms.MouseEventHandler(this.snapscreen_MouseMove);
            this.MouseUp += new System.Windows.Forms.MouseEventHandler(this.snapscreen_MouseUp);
            this.ResumeLayout(false);

        }

        #endregion

    }
}

3.cs文件的代码：

[code] using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace Graphics
{
    public partial class snapscreen : Form
    {
        System.Drawing.Graphics global_graphics;
        Pen pen = new Pen(Brushes.Black);
        private Point DownPoint;
        private bool isEditting = false;
        private Bitmap originBmp;
        private Rectangle catchRect;
        public snapscreen()
        {
            InitializeComponent();
            global_graphics = this.CreateGraphics();
        }

        private void snapscreen_Load(object sender, EventArgs e)
        {
            originBmp = new Bitmap(this.BackgroundImage);
        }

        private void snapscreen_KeyDown(object sender, KeyEventArgs e)
        {
            if (e.KeyCode == Keys.Escape)
            {
                this.Close();
            }
        }

        private void snapscreen_MouseDown(object sender, MouseEventArgs e)
        {
            DownPoint = e.Location;
            isEditting = true;
        }

        private void snapscreen_MouseUp(object sender, MouseEventArgs e)
        { 
            isEditting = false;
        }

        private void snapscreen_MouseMove(object sender, MouseEventArgs e)
        { 
            if(isEditting == true)
            {
                Point nowPoint = e.Location;

                int x1 = Math.Min(DownPoint.X, nowPoint.X);
                int y1 = Math.Min(DownPoint.Y, nowPoint.Y);

                int width =  Math.Max(DownPoint.X, nowPoint.X) - Math.Min(DownPoint.X, nowPoint.X);
                int height = Math.Max(DownPoint.Y, nowPoint.Y) - Math.Min(DownPoint.Y, nowPoint.Y);

                //基于背景图创建一个画布，并绘制矩形，然后在窗体上显示
                Bitmap destBmp = (Bitmap)originBmp.Clone();
                //在新建图片上创建画板
                System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(destBmp);

                catchRect = new Rectangle(new Point(x1, y1), new Size(width, height));

                Pen p1 = new Pen(Color.Black, 1);
                g.DrawRectangle(p1, catchRect); //将矩形绘制到画板上
                g.Dispose(); //释放目前的画板

                p1.Dispose();
                global_graphics.DrawImage(destBmp, new Point(0, 0));
                destBmp.Dispose(); 

            }

        }

        private void snapscreen_MouseDoubleClick(object sender, MouseEventArgs e)
        {
            if (catchRect.Contains(new Point(e.X, e.Y)))
            {
                Image CatchedBmp = new Bitmap(catchRect.Width, catchRect.Height);
                System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(CatchedBmp); //创建图片画布 
                //源范围
                Rectangle sourceRectangle = new Rectangle(0, 0, catchRect.Width, catchRect.Height);
                //目标范围 catchRect

                g.DrawImage(originBmp, sourceRectangle, catchRect, GraphicsUnit.Pixel); 
                Clipboard.SetImage(CatchedBmp);//将图片保存到剪贴板
                g.Dispose();
                CatchedBmp.Dispose();
                originBmp.Dispose();

                this.Close();
                this.Dispose();
            }
        }
    }
}

主要思路：

(1) 全屏的截屏文件保存在内存中，并基于该图片创建一个画布 graphics1

(2) 在mousemove事件中，向graphics1 画布上添加矩形边线(对应着截图区)

(3) 在mousedoubleclick事件中，若点击坐标在矩形选区内，则视作保存选区。

(4)创建一个与选区相同大小的image，将选区复制到该图片中。

(5)调用剪贴板函数 Clipboard.SetImage(CatchedBmp);//将图片保存到剪贴板