如何将从 C# 发送到 C++ dll 的图像数据重建回图像

Question

我正在将图像数据从 C# 脚本发送到 C++ dll。 我想知道如何将这些数据转换回 C++ 端的图像，以便可以使用 GDI+ 显示。

C# 代码

[DllImport("ExtWindow")] 
private static extern void SetImage(IntPtr img, int width, int height);
(...)
        using (var bmp = new Bitmap(@"D:/my_image.png"))
        {
            BitmapData data = bmp.LockBits(new Rectangle(0, 0, bmp.Width, bmp.Height), ImageLockMode.ReadWrite, bmp.PixelFormat);

            SetImage(bmp.GetHbitmap(), bmp.Width, bmp.Height);

            bmp.UnlockBits(data);
        }

C++ 代码

Bitmap* display_img;

extern "C" void __declspec(dllexport) SetImage(void* data, int width, int height) {
    HBITMAP hBmp = CreateBitmap(width, height, 1, 24, data);

    display_img = (Bitmap*)Bitmap::FromHBITMAP(hBmp, NULL); // <=== i fail to properly convert here

    // Force WM_PAINT
    RedrawWindow(my_hWnd, 0, 0, RDW_INVALIDATE | RDW_UPDATENOW);
}

(...) // A window is created earlier, which is where the image will be displayed

LRESULT CALLBACK newWndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam) {
    switch (message)
    {
    case WM_PAINT:
        // Display the image
        PAINTSTRUCT ps;
        HDC hdc = BeginPaint(hWnd, &ps);
        FillRect(hdc, &ps.rcPaint, (HBRUSH)(COLOR_WINDOW + 1));
        Graphics graphics(hdc);
        graphics.DrawImage(display_img, 0, 0);
        EndPaint(hWnd, &ps);
        return 0;
    }
    return DefWindowProc(hWnd, message, wParam, lParam);
}

Answer 1

假设它是相同的过程，您可以传递HBITMAP句柄。 除非您直接访问这些位，否则您不需要锁定这些位（这通常在进程间操作中是必需的）

在 C# 侧：

SetImage(bmp.GetHbitmap());

在 C++ 端，确保您已调用Gdiplus::GdiplusStartup例程，并读取HBITMAP 。 可以直接用GDI打印hbitmap ，也可以转换成Gdiplus::Bitmap在Gdiplus中打印

HBITMAP g_hbitmap = NULL;

extern "C" void __declspec(dllexport) SetImage(HBITMAP hbmp) {
    RedrawWindow(my_hWnd, 0, 0, RDW_INVALIDATE | RDW_UPDATENOW);
}

...
case WM_PAINT:
...
if (g_hbitmap)
{
    Gdiplus::Bitmap bitmap(g_hbitmap, NULL);
    Gdiplus::Graphics gr(hdc);
    Gdiplus::Status status = gr.DrawImage(&bitmap, 0, 0);
    //check status

    //clean up here, or elsewhere
    DeleteObject(g_hbitmap);
    g_hbitmap = NULL;
}