C#实现截图工具小项目

using System;
using System.Runtime.InteropServices;
using System.Windows.Forms;
 
namespace test {
    /// <summary>
    /// 热键类
    /// </summary>
    public class HotKey {
        /// <summary>
        /// 如果函数执行成功，返回值不为0，如果执行失败，返回值为0
        /// </summary>
        /// <returns></returns>
        [DllImport("user32.dll", SetLastError = true)]
        public static extern bool RegisterHotKey(
            IntPtr hWnd,           // 窗口的句柄, 当热键按下时，会产生WM_HOTKEY信息，该信息该会发送该窗口句柄
            int id,                      // 定义热键ID,属于唯一标识热键的作用
            uint fsModifiers,            // 热键只有在按下Alt、 Ctrl、Shift、Windows等键时才会生效，即才会产生WM_HOTKEY信息
            Keys vk                   // 虚拟键,即按了Alt+Ctrl+ X ，X就是代表虚拟键
            );
 
        [DllImport("user32.dll", SetLastError = true)]
        public static extern bool UnregisterHotKey(
            IntPtr hWnd,                   // 窗口句柄
            int id                         // 要取消热键的ID
            );
    }
}

using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.Threading;
using System.Timers;
using System.Windows.Forms;
 
namespace test {
    public partial class Form1 : Form {
 
        [Flags]
        public enum KeyModifiers { //定义热键值字符串(热键值是系统规定的，不能改变)
            None = 0,
            Alt = 1,
            Ctrl = 2,
            Shift = 4,
            WindowsKey = 8
        }
 
        public Form1() {
            InitializeComponent();
        }
 
        //窗体加载时-注册快捷键
        private void Form1_Load(object sender, EventArgs e) {
            uint ctrlHotKey = (uint)(KeyModifiers.Alt | KeyModifiers.Ctrl);
            // 注册热键为Alt+Ctrl+A, "100"为唯一标识热键
            HotKey.RegisterHotKey(Handle,100,ctrlHotKey,Keys.A);
        }
 
        //截图按钮
        private void button1_Click(object sender, EventArgs e) {
            if (this.WindowState != FormWindowState.Minimized) {
                this.WindowState = FormWindowState.Minimized;
                Thread.Sleep(200);
            }
            int swidth = Screen.PrimaryScreen.Bounds.Width;
            int sheight = Screen.PrimaryScreen.Bounds.Height;
            Bitmap btm = new Bitmap(swidth,sheight); //空图与屏幕同大小
            Graphics g = Graphics.FromImage(btm); //空图的画板
            g.CopyFromScreen(new Point(0,0),new Point(0,0),new Size(swidth,sheight)); //将屏幕内容复制到空图
            Cutter cutter = new Cutter(btm); //传送截图
            cutter.FormBorderStyle = FormBorderStyle.None; //截图全屏，无边框
            cutter.BackgroundImage = btm; //新的窗体截图做背景
            cutter.Show();
        }
        private void tiaoZ(object sender, ElapsedEventArgs e) {
        }
        
 
        //窗体关闭-取消热键
        private void Form1_FormClosing(object sender, FormClosingEventArgs e) {
            HotKey.UnregisterHotKey(Handle,100);
        }
 
        //快捷键按下执行的事件
        private void GlobalKeyProcess() {
            this.WindowState = FormWindowState.Minimized;
            Thread.Sleep(200);
            button1.PerformClick();
        }
 
        //重写。监视系统消息，调用对应方法
        protected override void WndProc(ref Message m) {
            const int WM_HOTKEY = 0x0312;
            //如果m.Msg的值为0x0312（我也不知道为什么是0x0312）那么表示用户按下了热键
            switch (m.Msg) {
                case WM_HOTKEY:
                    if (m.WParam.ToString().Equals("100")) {
                        GlobalKeyProcess();
                    }
                    //todo  其它热键
                    break;
            }
            // 将系统消息传递自父类的WndProc
            base.WndProc(ref m);
        }
    }
}

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
 
namespace test {
    public partial class Cutter : Form {
        Bitmap screenBtmp = null; //电脑屏幕的截图
 
        public Cutter(Bitmap btm) {
            InitializeComponent();
            screenBtmp = btm;
        }
 
        //鼠标右键退出
        private void Cutter_MouseClick(object sender, MouseEventArgs e) {
            if (e.Button == MouseButtons.Right) {
                this.DialogResult = DialogResult.OK;
                this.Close();
            }
        }
 
        bool CatchStart = false; //自由截图开始
        Point downPoint; //初始点
        //鼠标左键按下-开始自由截图
        private void Cutter_MouseDown(object sender, MouseEventArgs e) {
            if (e.Button == MouseButtons.Left) {
                if (!CatchStart) {
                    CatchStart = true;
                    downPoint = new Point(e.X,e.Y); //初始点
                }
            }
        }
 
        Rectangle catchRec;//存放截取范围
        //鼠标移动-绘制自由截图路径
        private void Cutter_MouseMove(object sender, MouseEventArgs e) { //路径绘制，核心
            if (CatchStart) {
                //
                //二次缓冲
                //不是直接在控件的背景画板上进行绘制鼠标移动路径，那样会造成绘制很多路径，因为前面绘制的路径还在
                //而是在内存中每移动一次鼠标就创建一张和屏幕截图一样的新BImtap,在这个Bitmap中绘制鼠标移动路径
                //然后在窗体背景画板上，绘制这个新的Bitmap,这样就不会造成绘制很多路径，因为每次都绘制了全新的Bitmao
                //但是这样做的话，因为鼠标移动的次数是大量的，所以在内存中会创建大量的Bitmap会造成内存消耗严重，所以每次移动绘制完后，
                //需要释放Dispose() 画板，画笔，Bitmap资源。
                //
                Bitmap copyBtmp = (Bitmap)screenBtmp.Clone(); //创建新的,在其上绘制路径
                //左上角
                Point firstP = new Point(downPoint.X,downPoint.Y);
                //新建画板，画笔
                Graphics g = Graphics.FromImage(copyBtmp);
                Pen p = new Pen(Color.Red,1);
                //计算路径范围
                int width = Math.Abs(e.X - downPoint.X);
                int height = Math.Abs(e.Y - downPoint.Y);
                if (e.X < downPoint.X) {
                    firstP.X = e.X;
                }
                if (e.Y < downPoint.Y) {
                    firstP.Y = e.Y;
                }
                //绘制路径
                catchRec = new Rectangle(firstP,new Size(width,height));
                //将路径绘制在新的BItmap上，之后要释放
                g.DrawRectangle(p, catchRec);
                g.Dispose();
                p.Dispose();
 
                //窗体背景画板
                Graphics gf = this.CreateGraphics();
                //将新图绘制在窗体的画板上   --   自由截图-路径绘制处，其实还是一张和屏幕同样大小的图片，只不过上面有红色的选择路径
                gf.DrawImage(copyBtmp,new Point(0,0));
                gf.Dispose();
                //释放内存Bimtap
                copyBtmp.Dispose();
                
            }
        }
 
        bool catchFinished = false; //自由截图结束标志
        //鼠标左键弹起-结束自由截图
        private void Cutter_MouseUp(object sender, MouseEventArgs e) {
            if (e.Button == MouseButtons.Left) {
                if (CatchStart) {
                    CatchStart = false;
                    catchFinished = true;
                }
            }
        }
 
        //鼠标左键双击，保存自由截取的图片
        private void Cutter_MouseDoubleClick(object sender, MouseEventArgs e) {
            if((e.Button == MouseButtons.Left) && catchFinished){
                //创建用户截取的范围大小的空图
                Bitmap catchBtmp = new Bitmap(catchRec.Width,catchRec.Height);
                Graphics g = Graphics.FromImage(catchBtmp);
                //在原始的屏幕截图ScreenBitmap上 截取 用户选择范围大小的区域   绘制到上面的空图
                //绘制完后，这个空图就是我们想要的截取的图片
                //参数1  原图
                //参数2  在空图上绘制的范围区域
                //参数3  原图的截取范围
                //参数4  度量单位
                g.DrawImage(screenBtmp,new Rectangle(0,0,catchRec.Width,catchRec.Height),catchRec,GraphicsUnit.Pixel);
 
                //将自由截取的图片保存到剪切板中
                Clipboard.Clear();
                Clipboard.SetImage(catchBtmp);
                g.Dispose();
                catchFinished = false;
                this.BackgroundImage = screenBtmp;
                catchBtmp.Dispose();
                this.DialogResult = DialogResult.OK;
                this.Close();
            }
        }
    }
}