c# – 将窗口绘制到图像文件

任何人都知道为什么这会一直返回空白图像？我发现这个功能 here.

我将句柄传递给记事本进程/窗口.

public static Image DrawToBitmap(IntPtr handle)
    {
        Bitmap image = new Bitmap(500,500,System.Drawing.Imaging.PixelFormat.Format32bppArgb);

        using (Graphics graphics = Graphics.FromImage(image))
        {
            IntPtr hDC = graphics.GetHdc();
            SendMessage(new HandleRef(graphics,handle),WM_PRINT,hDC,PRF_CHILDREN);
            graphics.ReleaseHdc(hDC);
        }
        return image;
    }

我这样使用以上内容：

Image myimage = DrawToBitmap(handle);

myimage.Save("C:\\here.png",ImageFormat.Png);

谢谢大家的帮助

更新

我想我已经设法从SendMessage使用以下代码获取错误代码：

if (SendMessage(handle,PRF_CLIENT))
{
    Console.WriteLine("Success!");
}
else
{
    Console.WriteLine("Error: " + Marshal.GetLastWin32Error());
}

我得到8的错误,我发现这意味着没有足够的内存？我有超过500MB免费！也许我理解这个错了？

解决方法

您可以使用Printwindow代替SendMessage

这是一个例子

public static Image DrawToBitmap(IntPtr handle)
{
    RECT rect = new RECT();
    GetwindowRect(handle,ref rect);

    Bitmap image = new Bitmap(rect.Right - rect.Left,rect.Bottom - rect.Top);

    using (Graphics graphics = Graphics.FromImage(image))
    {
        IntPtr hDC = graphics.GetHdc();
        Printwindow(new HandleRef(graphics,0);
        graphics.ReleaseHdc(hDC);
    }

    return image;
}

#region Interop

[DllImport("USER32.DLL")]
private static extern bool Printwindow(HandleRef hwnd,IntPtr hdcBlt,int nFlags);

[DllImport("user32.dll",SetLastError = true)]
[return: MarshalAs(UnmanagedType.Bool)]
private static extern bool GetwindowRect(IntPtr hWnd,ref RECT lpRect);

[StructLayout(LayoutKind.Sequential)]
private struct RECT
{
    public int Left;
    public int Top;
    public int Right;
    public int Bottom;
}

#endregion