Question

任何人都知道为什么这会一直返回空白图像？我找到了这个函数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;
    }

我像这样使用上面的内容：

Image myimage = DrawToBitmap(handle);

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

感谢大家的帮助

更新

我想我已经设法从SendMessage获取错误代码，使用以下内容：

if (SendMessage(handle, WM_PRINT, hDC, 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！也许我理解这个错误？

Answer 1

而不是SendMessage，您可以使用PrintWindow

这是一个示例

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, handle), hDC, 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

Answer 2

除了PRF_CHILDREN之外，尝试将PRF_CLIENT或PRF_NONCLIENT传递给SendMessage。

另外，您如何派生传递给函数的句柄？

将窗口绘制到图像文件

更新

2 个答案: