using System;
using System.Runtime.InteropServices;
using System.Windows.Forms;
 
namespace test {
    /// <summary>
    /// 熱鍵類
    /// </summary>
    public class HotKey {
        /// <summary>
        /// 如果函數(shù)執(zhí)行成功，返回值不為0，如果執(zhí)行失敗，返回值為0
        /// </summary>
        /// <returns></returns>
        [DllImport("user32.dll", SetLastError = true)]
        public static extern bool RegisterHotKey(
            IntPtr hWnd,           // 窗口的句柄, 當(dāng)熱鍵按下時(shí)，會(huì)產(chǎn)生WM_HOTKEY信息，該信息該會(huì)發(fā)送該窗口句柄
            int id,                      // 定義熱鍵ID,屬于唯一標(biāo)識(shí)熱鍵的作用
            uint fsModifiers,            // 熱鍵只有在按下Alt、 Ctrl、Shift、Windows等鍵時(shí)才會(huì)生效，即才會(huì)產(chǎn)生WM_HOTKEY信息
            Keys vk                   // 虛擬鍵,即按了Alt+Ctrl+ X ，X就是代表虛擬鍵
            );
 
        [DllImport("user32.dll", SetLastError = true)]
        public static extern bool UnregisterHotKey(
            IntPtr hWnd,                   // 窗口句柄
            int id                         // 要取消熱鍵的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 { //定義熱鍵值字符串(熱鍵值是系統(tǒng)規(guī)定的，不能改變)
            None = 0,
            Alt = 1,
            Ctrl = 2,
            Shift = 4,
            WindowsKey = 8
        }
 
        public Form1() {
            InitializeComponent();
        }
 
        //窗體加載時(shí)-注冊(cè)快捷鍵
        private void Form1_Load(object sender, EventArgs e) {
            uint ctrlHotKey = (uint)(KeyModifiers.Alt | KeyModifiers.Ctrl);
            // 注冊(cè)熱鍵為Alt+Ctrl+A, "100"為唯一標(biāo)識(shí)熱鍵
            HotKey.RegisterHotKey(Handle,100,ctrlHotKey,Keys.A);
        }
 
        //截圖按鈕
        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?qǐng)D與屏幕同大小
            Graphics g = Graphics.FromImage(btm); //空?qǐng)D的畫板
            g.CopyFromScreen(new Point(0,0),new Point(0,0),new Size(swidth,sheight)); //將屏幕內(nèi)容復(fù)制到空?qǐng)D
            Cutter cutter = new Cutter(btm); //傳送截圖
            cutter.FormBorderStyle = FormBorderStyle.None; //截圖全屏，無邊框
            cutter.BackgroundImage = btm; //新的窗體截圖做背景
            cutter.Show();
        }
        private void tiaoZ(object sender, ElapsedEventArgs e) {
        }
        
 
        //窗體關(guān)閉-取消熱鍵
        private void Form1_FormClosing(object sender, FormClosingEventArgs e) {
            HotKey.UnregisterHotKey(Handle,100);
        }
 
        //快捷鍵按下執(zhí)行的事件
        private void GlobalKeyProcess() {
            this.WindowState = FormWindowState.Minimized;
            Thread.Sleep(200);
            button1.PerformClick();
        }
 
        //重寫。監(jiān)視系統(tǒng)消息，調(diào)用對(duì)應(yīng)方法
        protected override void WndProc(ref Message m) {
            const int WM_HOTKEY = 0x0312;
            //如果m.Msg的值為0x0312（我也不知道為什么是0x0312）那么表示用戶按下了熱鍵
            switch (m.Msg) {
                case WM_HOTKEY:
                    if (m.WParam.ToString().Equals("100")) {
                        GlobalKeyProcess();
                    }
                    //todo  其它熱鍵
                    break;
            }
            // 將系統(tǒng)消息傳遞自父類的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; //電腦屏幕的截圖
 
        public Cutter(Bitmap btm) {
            InitializeComponent();
            screenBtmp = btm;
        }
 
        //鼠標(biāo)右鍵退出
        private void Cutter_MouseClick(object sender, MouseEventArgs e) {
            if (e.Button == MouseButtons.Right) {
                this.DialogResult = DialogResult.OK;
                this.Close();
            }
        }
 
        bool CatchStart = false; //自由截圖開始
        Point downPoint; //初始點(diǎn)
        //鼠標(biāo)左鍵按下-開始自由截圖
        private void Cutter_MouseDown(object sender, MouseEventArgs e) {
            if (e.Button == MouseButtons.Left) {
                if (!CatchStart) {
                    CatchStart = true;
                    downPoint = new Point(e.X,e.Y); //初始點(diǎn)
                }
            }
        }
 
        Rectangle catchRec;//存放截取范圍
        //鼠標(biāo)移動(dòng)-繪制自由截圖路徑
        private void Cutter_MouseMove(object sender, MouseEventArgs e) { //路徑繪制，核心
            if (CatchStart) {
                //
                //二次緩沖
                //不是直接在控件的背景畫板上進(jìn)行繪制鼠標(biāo)移動(dòng)路徑，那樣會(huì)造成繪制很多路徑，因?yàn)榍懊胬L制的路徑還在
                //而是在內(nèi)存中每移動(dòng)一次鼠標(biāo)就創(chuàng)建一張和屏幕截圖一樣的新BImtap,在這個(gè)Bitmap中繪制鼠標(biāo)移動(dòng)路徑
                //然后在窗體背景畫板上，繪制這個(gè)新的Bitmap,這樣就不會(huì)造成繪制很多路徑，因?yàn)槊看味祭L制了全新的Bitmao
                //但是這樣做的話，因?yàn)槭髽?biāo)移動(dòng)的次數(shù)是大量的，所以在內(nèi)存中會(huì)創(chuàng)建大量的Bitmap會(huì)造成內(nèi)存消耗嚴(yán)重，所以每次移動(dòng)繪制完后，
                //需要釋放Dispose() 畫板，畫筆，Bitmap資源。
                //
                Bitmap copyBtmp = (Bitmap)screenBtmp.Clone(); //創(chuàng)建新的,在其上繪制路徑
                //左上角
                Point firstP = new Point(downPoint.X,downPoint.Y);
                //新建畫板，畫筆
                Graphics g = Graphics.FromImage(copyBtmp);
                Pen p = new Pen(Color.Red,1);
                //計(jì)算路徑范圍
                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;
                }
                //繪制路徑
                catchRec = new Rectangle(firstP,new Size(width,height));
                //將路徑繪制在新的BItmap上，之后要釋放
                g.DrawRectangle(p, catchRec);
                g.Dispose();
                p.Dispose();
 
                //窗體背景畫板
                Graphics gf = this.CreateGraphics();
                //將新圖繪制在窗體的畫板上   --   自由截圖-路徑繪制處，其實(shí)還是一張和屏幕同樣大小的圖片，只不過上面有紅色的選擇路徑
                gf.DrawImage(copyBtmp,new Point(0,0));
                gf.Dispose();
                //釋放內(nèi)存Bimtap
                copyBtmp.Dispose();
                
            }
        }
 
        bool catchFinished = false; //自由截圖結(jié)束標(biāo)志
        //鼠標(biāo)左鍵彈起-結(jié)束自由截圖
        private void Cutter_MouseUp(object sender, MouseEventArgs e) {
            if (e.Button == MouseButtons.Left) {
                if (CatchStart) {
                    CatchStart = false;
                    catchFinished = true;
                }
            }
        }
 
        //鼠標(biāo)左鍵雙擊，保存自由截取的圖片
        private void Cutter_MouseDoubleClick(object sender, MouseEventArgs e) {
            if((e.Button == MouseButtons.Left) && catchFinished){
                //創(chuàng)建用戶截取的范圍大小的空?qǐng)D
                Bitmap catchBtmp = new Bitmap(catchRec.Width,catchRec.Height);
                Graphics g = Graphics.FromImage(catchBtmp);
                //在原始的屏幕截圖ScreenBitmap上 截取 用戶選擇范圍大小的區(qū)域   繪制到上面的空?qǐng)D
                //繪制完后，這個(gè)空?qǐng)D就是我們想要的截取的圖片
                //參數(shù)1  原圖
                //參數(shù)2  在空?qǐng)D上繪制的范圍區(qū)域
                //參數(shù)3  原圖的截取范圍
                //參數(shù)4  度量單位
                g.DrawImage(screenBtmp,new Rectangle(0,0,catchRec.Width,catchRec.Height),catchRec,GraphicsUnit.Pixel);
 
                //將自由截取的圖片保存到剪切板中
                Clipboard.Clear();
                Clipboard.SetImage(catchBtmp);
                g.Dispose();
                catchFinished = false;
                this.BackgroundImage = screenBtmp;
                catchBtmp.Dispose();
                this.DialogResult = DialogResult.OK;
                this.Close();
            }
        }
    }
}