using System;
using System.Runtime.InteropServices;
using System.Drawing;
using System.Drawing.Imaging;

namespace CSharpChat
{
 /// <summary>
 /// ScreenCameraClass 的摘要说明。
 /// </summary>
 public class ScreenCameraClass
 {
  public ScreenCameraClass()
  {
   //
   // TODO: 在此处添加构造函数逻辑
   //
  }
  /**//// <summary>
  /// Creates an Image object containing a screen shot of the entire desktop?
  /// </summary>
  /// <returns></returns>
  public Image CaptureScreen()
  {
   return CaptureWindow( User32.GetDesktopWindow() );
  }
 
  /**//// <summary>
  /// Creates an Image object containing a screen shot of a specific window?
  /// </summary>
  /// <param name="handle">The handle to the window. (In windows forms, this is obtained by the Handle property)</param>
  /// <returns></returns>
  public Image CaptureWindow(IntPtr handle)
  {
   // get te hDC of the target window
   IntPtr hdcSrc = User32.GetWindowDC(handle);
   // get the size
   User32.RECT windowRect = new User32.RECT();
   User32.GetWindowRect(handle,ref windowRect);
   int width = windowRect.right - windowRect.left;
   int height = windowRect.bottom - windowRect.top;
   // create a device context we can copy to
   IntPtr hdcDest = GDI32.CreateCompatibleDC(hdcSrc);
   // create a bitmap we can copy it to,
   // using GetDeviceCaps to get the width/height
   IntPtr hBitmap = GDI32.CreateCompatibleBitmap(hdcSrc,width,height);
   // select the bitmap object
   IntPtr hOld = GDI32.SelectObject(hdcDest,hBitmap);
   // bitblt over
   GDI32.BitBlt(hdcDest,0,0,width,height,hdcSrc,0,0,GDI32.SRCCOPY);
   // restore selection
   GDI32.SelectObject(hdcDest,hOld);
   // clean up
   GDI32.DeleteDC(hdcDest);
   User32.ReleaseDC(handle,hdcSrc);

   // get a .NET image object for it
   Image img = Image.FromHbitmap(hBitmap);
   // free up the Bitmap object
   GDI32.DeleteObject(hBitmap);

   return img;
  }

  /**//// <summary>
  /// Captures a screen shot of a specific window, and saves it to a file?
  /// </summary>
  /// <param name="handle"></param>
  /// <param name="filename"></param>
  /// <param name="format"></param>
  public void CaptureWindowToFile(IntPtr handle, string filename, ImageFormat format)
  {
   Image img = CaptureWindow(handle);
   img.Save(filename,format);
  }

  /**//// <summary>
  /// Captures a screen shot of the entire desktop, and saves it to a file?
  /// </summary>
  /// <param name="filename"></param>
  /// <param name="format"></param>
  public void CaptureScreenToFile(string filename, ImageFormat format)
  {
   Image img = CaptureScreen();
   img.Save(filename,format);
  }
     
  /**//// <summary>
  /// Helper class containing Gdi32 API functions
  /// </summary>
  private class GDI32
  {
           
   public const int SRCCOPY = 0x00CC0020; // BitBlt dwRop parameter

   [DllImport("gdi32.dll")]
   public static extern bool BitBlt(IntPtr hObject,int nXDest,int nYDest,
    int nWidth,int nHeight,IntPtr hObjectSource,
    int nXSrc,int nYSrc,int dwRop);
   [DllImport("gdi32.dll")]
   public static extern IntPtr CreateCompatibleBitmap(IntPtr hDC,int nWidth,
    int nHeight);
   [DllImport("gdi32.dll")]
   public static extern IntPtr CreateCompatibleDC(IntPtr hDC);
   [DllImport("gdi32.dll")]
   public static extern bool DeleteDC(IntPtr hDC);
   [DllImport("gdi32.dll")]
   public static extern bool DeleteObject(IntPtr hObject);
   [DllImport("gdi32.dll")]
   public static extern IntPtr SelectObject(IntPtr hDC,IntPtr hObject);
  }
 
  /**//// <summary>
  /// Helper class containing User32 API functions
  /// </summary>
  private class User32
  {
   [StructLayout(LayoutKind.Sequential)]
    public struct RECT
   {
    public int left;
    public int top;
    public int right;
    public int bottom;
   }

   [DllImport("user32.dll")]
   public static extern IntPtr GetDesktopWindow();
   [DllImport("user32.dll")]
   public static extern IntPtr GetWindowDC(IntPtr hWnd);
   [DllImport("user32.dll")]
   public static extern IntPtr ReleaseDC(IntPtr hWnd,IntPtr hDC);
   [DllImport("user32.dll")]
   public static extern IntPtr GetWindowRect(IntPtr hWnd,ref RECT rect);

  }
 }
}