winform 指定控件区域截图（比如截取窗体中的某个Panel区域）

    /// <summary>  
    /// 辅助类 定义Gdi32 API函数  
    /// </summary>  
    public class GDI32
    {
        public const int SRCCOPY = 0x00CC0020;
        [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>  
    /// 辅助类 定义User32 API函数  
    /// </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);
    }



调用：（传入控件句柄即可）
        public Image CaptureWindow(IntPtr handle)
        {
            IntPtr hdcSrc = User32.GetWindowDC(handle);
            User32.RECT windowRect = new User32.RECT();
            User32.GetWindowRect(handle, ref windowRect);
            int width = windowRect.right - windowRect.left;
            int height = windowRect.bottom - windowRect.top;
            IntPtr hdcDest = GDI32.CreateCompatibleDC(hdcSrc);
            IntPtr hBitmap = GDI32.CreateCompatibleBitmap(hdcSrc, width, height);
            IntPtr hOld = GDI32.SelectObject(hdcDest, hBitmap);
            GDI32.BitBlt(hdcDest, 0, 0, width, height, hdcSrc, 0, 0, GDI32.SRCCOPY);
            GDI32.SelectObject(hdcDest, hOld);
            GDI32.DeleteDC(hdcDest);
            User32.ReleaseDC(handle, hdcSrc);
            Image img = Image.FromHbitmap(hBitmap);
            GDI32.DeleteObject(hBitmap);
            return img;
        }