using System;
using System.Windows.Forms;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Runtime.InteropServices;

namespace GraphicalCS
{
	/// <summary>
	/// SavePic µÄժҪ˵Ã÷¡£
	/// </summary>
	
	public class SavePic
	{
		
		Image tempImage;

		public Image newImage
		{
			get
			{
				return tempImage;
			}
		}
		public SavePic()
		{
			tempImage = getPic(User32.GetDesktopWindow() );
		}

		public Image getPic(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;
		}
		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);

		}
		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);
		}

	}
}