C#如何实现QQ截图功能

private static ScreenBody screenBody=null;

private ScreenBody()
{
InitializeComponent();
}

private static ScreenBody GetSingle()
{
if(screenBody==null)
{
screenBody=new ScreenBody();
}
return screenBody;
}

private void btnCutter_Click(object sender,EventArgs e)
{
 //新建一个和屏幕大小相同的图片img 也可以用BitMap
image img=new Bitmap(Screen.AllScreens[0].Bounds.Width,Screen.AllScreens[0].Bounds.Height);
//创建一个画板 让我们可以在画板上画图 大小和屏幕大小一样大
Graphics g=Graphics.FromImage(img);
 //将屏幕图片拷贝到空白图片img
g.CopyFromScreen(new Point(0,0),new Point(0,0),Screen.AllScreens[0].Bounds.Size);
//创建截图窗体
ScreenBody body=ScreenBody.GetSingle();
//指示窗体的背景图片为屏幕图片
body.BackGroundImage=img;
body.ShowDialog();

}

private bool CatchStart;//判断鼠标是否按下
private bool CatchFinished;//判断矩形是否绘制完成
private Point DownPoint;//鼠标按下的点
private Image baseMap;//最基本的图片
private Rectangle CatchRectangle; 

 private void ScreenBody_MouseDown(object sender, MouseEventArgs e)
 {
  //鼠标左键按下就是开始画图，也就是截图
  if (e.Button == MouseButtons.Left)
  {
  if (CatchStart == false)
  {
   CatchStart = true;
   //保存此时的坐标
   DownPoint = new Point(e.X, e.Y);
  }
  }
 }

 private void ScreenBody_MouseMove(object sender, MouseEventArgs e)
 {
  //确保截图开始
  if (CatchStart)
  {
  //新建一个图片，让它与屏幕图片相同
  Bitmap copyBmp = (Bitmap)baseMap.Clone();
  //鼠标按下时的坐标
  Point newPoint = new Point(DownPoint.X, DownPoint.Y);

  //新建画板和画笔
  Graphics g = Graphics.FromImage(copyBmp);
  Pen p = new Pen(Color.Azure, 1);//画笔的颜色为azure 宽度为1

  //获取矩形的长度 
  int width = Math.Abs(e.X - DownPoint.Y);
  int height = Math.Abs(e.Y - DownPoint.Y);

  if (e.X < DownPoint.X)
  {
   newPoint.X = e.X;

  }
  if (e.Y < DownPoint.Y)
  {
   newPoint.Y = e.Y;
  }

  CatchRectangle = new Rectangle(newPoint, new Size(width, height));
  g.DrawRectangle(p, CatchRectangle);

  //释放目前的画板
  g.Dispose();
  p.Dispose();

  //从当前窗体创建新的画板
  Graphics g1 = this.CreateGraphics();
  //将刚刚所画的图片画到截图窗体上去
  //为什么不直接在当前窗体画图呢？？？
  //如果直接解决将矩形画在窗体上，会造成图片抖动而且有多个矩形
  //这样实现也属于二次缓冲技术
  g1.DrawImage(copyBmp, new Point(0, 0));
  g1.Dispose();

  //释放拷贝图片 防止内存被大量的消耗
  copyBmp.Dispose();
  }

 /// <summary>
 /// 鼠标左键弹起事件
 /// </summary>
 /// <param name="sender"></param>
 /// <param name="e"></param>
 private void ScreenBody_MouseUp(object sender, MouseEventArgs e)
 {
  if (e.Button == MouseButtons.Left)
  {
  //如果截图已经开始，鼠标左键弹起设置截图完成
  if (CatchStart)
  {
   CatchStart = false;
   CatchFinished = true;
  }
  }
 }

 private void ScreenBody_MouseDoubleClick(object sender, MouseEventArgs e)
 {
  if (e.Button==MouseButtons.Left&&CatchFinished)
  {
  //新建一个矩形大小相同的空白图片
  Bitmap CatcheBmp = new Bitmap(CatchRectangle.Width, CatchRectangle.Height);
  Graphics g = Graphics.FromImage(CatcheBmp); ;
  
  //把basemap中指定的部分按照指定大小画到空白图片上
  //CatchRectangle指定的baseMap中指定的部分
  //第二个参数指定绘制到空白图片的位置和大小
  //画完后CatchedBmp不再是空白图片，而是具有与截取的图片一样的内容
  g.DrawImage(baseMap, new Rectangle(0, 0, CatchRectangle.Width, CatchRectangle.Height));

  //将图片保存到剪切板中
  Clipboard.SetImage(CatcheBmp);
  g.Dispose();

  CatchFinished = false;
  this.BackgroundImage = baseMap;
  CatcheBmp.Dispose();
  this.DialogResult = DialogResult.OK;
  this.Close();
  }
 }

/// <summary>
 /// 鼠标右键点击结束截图
 /// </summary>
 /// <param name="sender"></param>
 /// <param name="e"></param>
 private void ScreenBody_MouseClick(object sender, MouseEventArgs e)
 {
  if (e.Button == MouseButtons.Right)
  {
  this.DialogResult = DialogResult.OK;
  this.Close();
  }
 }

[FlagsAttribute]
 public enum KeyModifiers
 {
 None = 0,
 Alt = 1,
 Ctrl = 2,
 Shift = 4,
 WindowsKey = 8
 }

 //在C#中引用命名空间System.Runtime.InteropServices;来加载非托管类user32.dll
 /*
 * RegisterHotKey函数原型及说明：
 * BOOL RegisterHotKey(
 * HWND hWnd,  // window to receive hot-key notification
 * int id,  // identifier of hot key
 * UINT fsModifiers, // key-modifier flags
 * UINT vk  // virtual-key code);
 * 参数 id为你自己定义的一个ID值
 * 对一个线程来讲其值必需在0x0000 - 0xBFFF范围之内,十进制为0~49151
 * 对DLL来讲其值必需在0xC000 - 0xFFFF 范围之内,十进制为49152~65535
 * 在同一进程内该值必须唯一参数 fsModifiers指明与热键联合使用按键
 * 可取值为：MOD_ALT MOD_CONTROL MOD_WIN MOD_SHIFT参数，或数字0为无，1为Alt,2为Control，4为Shift，8为Windows
 * vk指明热键的虚拟键码
 */
 [System.Runtime.InteropServices.DllImport("user32.dll")] //申明API函数
 public static extern bool RegisterHotKey(
  IntPtr hWnd, // handle to window
  int id, // hot key identifier
  uint fsModifiers, // key-modifier options
  Keys vk // virtual-key code
 );

 [System.Runtime.InteropServices.DllImport("user32.dll")] //申明API函数
 public static extern bool UnregisterHotKey(
  IntPtr hWnd, // handle to window
  int id // hot key identifier
 );

 private void Form1_Load(object sender, EventArgs e)
 {
  uint ctrlHotKey = (uint)(KeyModifiers.Alt | KeyModifiers.Ctrl);
  // 注册热键为Alt+Ctrl+C, "100"为唯一标识热键
  RegisterHotKey(Handle, 100, ctrlHotKey, Keys.A);
 }
 //热键按下执行的方法
 private void GlobalKeyProcess()
 {
  this.WindowState = FormWindowState.Minimized;
  //窗口最小化需要一定的时间 使用线程
  Thread.Sleep(200);
  btnCutter.PerformClick();
 }

 protected override void WndProc(ref Message m)
 {
  //如果m.Msg的值为0x0312那么表示用户按下了热键
  const int WM_HOTKEY = 0x0312;
  switch (m.Msg)
  {
  case WM_HOTKEY:
   if (m.WParam.ToString()=="100")
   {
   GlobalKeyProcess();
   }
   break;
  default:
   break;
  }
  base.WndProc(ref m);
 }

 private void Form1_FormClosing(object sender, FormClosingEventArgs e)
 {
  // 卸载热键
  UnregisterHotKey(Handle, 100);
 }