BitBlt 函数 详解2 附Demo

        public static Bitmap GetWindowCapture(IntPtr handle, int width, int height)
        {
            try
            {
                // get the hDC of the target window
                IntPtr hdcSrc = User32.GetWindowDC(handle);
                // 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
                Bitmap img = Image.FromHbitmap(hBitmap);
                // free up the Bitmap object
                GDI32.DeleteObject(hBitmap);

                return img;
            }
            catch (Exception ex)
            {
                LogHelper.Execption(ex, nameof(ImageHelper));
            }
            return null;
        }


        /// <summary>  
        /// Helper class containing Gdi32 API functions  
        /// </summary>  
        public class GDI32
        {
            public const int CAPTUREBLT = 1073741824;
            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>  
        public 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);


            public const int WM_PAINT = 0x000F;
            [DllImport("user32.dll", EntryPoint = "SendMessageA")]
            public static extern uint SendMessage(IntPtr hWnd, int wMsg, IntPtr wParam, IntPtr lParam);


            [DllImport("user32.dll")]
            public static extern bool PrintWindow(
                IntPtr hwnd,                // Window to copy,Handle to the window that will be copied.
                IntPtr hdcBlt,              // HDC to print into,Handle to the device context.
                UInt32 nFlags               // Optional flags,Specifies the drawing options. It can be one of the following values.
                );

            [DllImport("user32.dll", CharSet = CharSet.Auto, ExactSpelling = true)]
            public static extern int ShowWindow(IntPtr hwnd, int nCmdShow);

            #region  窗口关联
            //            nCmdShow的含义
            //0 关闭窗口
            //1 正常大小显示窗口
            //2 最小化窗口
            //3 最大化窗口
            //使用实例: ShowWindow(myPtr, 0);
            #endregion
        }