BitBlt 转换为字节数组并从 C++ 解析为 C#

Question

我正在尝试用 C++ 创建屏幕捕获 DLL，并将生成的字节数组发送到 C#。

我能够获得返回给 C# 的大小，但字节数组始终为空。

这是 C++ 代码（由我在 Internet 上找到的位组成）

    __declspec(dllexport) int ScreenCap(BYTE* *data, DWORD *size)
{
    try
    {
    //BITMAP bmpScreen;
    HWND DesktopHwnd = GetDesktopWindow();
    RECT DesktopParams;
    HDC DevC = GetDC(DesktopHwnd);
    GetWindowRect(DesktopHwnd,&DesktopParams);
    DWORD Width = DesktopParams.right - DesktopParams.left;
    DWORD Height = DesktopParams.bottom - DesktopParams.top;

    DWORD FileSize = sizeof(BITMAPFILEHEADER)+sizeof(BITMAPINFOHEADER)+(sizeof(RGBTRIPLE)+1*(Width*Height*4));
    *size = FileSize;
    char *BmpFileData = (char*)GlobalAlloc(0x0040,FileSize);

    PBITMAPFILEHEADER BFileHeader = (PBITMAPFILEHEADER)BmpFileData;
    PBITMAPINFOHEADER  BInfoHeader = (PBITMAPINFOHEADER)&BmpFileData[sizeof(BITMAPFILEHEADER)];

    BFileHeader->bfType = 0x4D42; // BM
    BFileHeader->bfSize = sizeof(BITMAPFILEHEADER);
    BFileHeader->bfOffBits = sizeof(BITMAPFILEHEADER)+sizeof(BITMAPINFOHEADER);

    BInfoHeader->biSize = sizeof(BITMAPINFOHEADER);
    BInfoHeader->biPlanes = 1;
    BInfoHeader->biBitCount = 24;
    BInfoHeader->biCompression = BI_RGB;
    BInfoHeader->biHeight = Height;
    BInfoHeader->biWidth = Width;

    RGBTRIPLE *Image = (RGBTRIPLE*)&BmpFileData[sizeof(BITMAPFILEHEADER)+sizeof(BITMAPINFOHEADER)];
    RGBTRIPLE color;

    HDC CaptureDC = CreateCompatibleDC(DevC);
    HBITMAP CaptureBitmap = CreateCompatibleBitmap(DevC,Width,Height);
    SelectObject(CaptureDC,CaptureBitmap);
    BOOL bRet = BitBlt(CaptureDC,0,0,Width,Height,DevC,0,0,SRCCOPY|CAPTUREBLT);
    //GetDIBits(CaptureDC,CaptureBitmap,0,Height,Image,(LPBITMAPINFO)BInfoHeader, DIB_RGB_COLORS);
    //GetObject(CaptureBitmap,sizeof(BITMAPFILEHEADER),&bmpScreen);
    //BYTE* lpPixels = new BYTE[sizeof((LPBITMAPINFO)BInfoHeader)];
    GetDIBits(CaptureDC, CaptureBitmap, 0, Height, *data, (LPBITMAPINFO)BInfoHeader, DIB_RGB_COLORS);
    //DWORD Junk;
    //DIBSECTION dib;
    //GetObject(CaptureBitmap, sizeof(dib), (LPVOID)&dib);

    //HANDLE FH = CreateFileA(BmpName,GENERIC_WRITE,FILE_SHARE_WRITE,0,CREATE_ALWAYS,0,0);
    //WriteFile(FH,BmpFileData,FileSize,&Junk,0);
    //CloseHandle(FH);
        GlobalFree(BmpFileData); 


        return 1;
    }
    catch(char *p)
    {
        return 0;
    }
}

这是我使用 "ref" 关键字的 C# 代码。

        [DllImport("consoleapplication1.dll", CallingConvention = CallingConvention.Cdecl)]
        static extern int ScreenCap(ref byte[] data, ref int size);

        public static void CapScreen()
    {
        try
        {
            int hr = 0;
            byte[] gData = null;
            int gSize = 0;
            hr = ScreenCap(ref gData, ref gSize);
            int a = 1;
        }
        catch(Exception ex)
        {
            int a = 1;
        }

我认为我的 GetDIBits 可能有问题，但我不确定。我希望你们中的一些大师可以让我走上正确的道路。谢谢。

* 编辑 *

好的非常感谢 jdweng 和 filip 为我指明了正确的方向。我现在接收屏幕作为 IntPtr 并能够将其呈现到我的 C# 应用程序。这是现在可以使用的代码（我会在底部解释）

__declspec(dllexport) char* ScreenCap(DWORD * size)

{ 尝试 { // 获取屏幕尺寸 int nScreenWidth = GetSystemMetrics(SM_CXSCREEN); int nScreenHeight = GetSystemMetrics(SM_CYSCREEN);

    *size = ((((24 * nScreenWidth + 31)&(~31)) / 8)*nScreenHeight);

    BITMAPINFO MyBMInfo = {0};
    MyBMInfo.bmiHeader.biSize = sizeof(MyBMInfo.bmiHeader); 

    // Create compatible DC, create a compatible bitmap and copy the screen using BitBlt()
    HDC hdcScreen = GetDC(GetDesktopWindow());
    HDC hdcCompatible  = CreateCompatibleDC(hdcScreen);
    HBITMAP hBmp = CreateCompatibleBitmap(hdcScreen, nScreenWidth, nScreenHeight);
    //HGDIOBJ hOldBmp = SelectObject(hdcCompatible, hBmp); 
    HGDIOBJ hOldBmp = (HGDIOBJ) SelectObject(hdcCompatible, hBmp);

    BOOL bOK = BitBlt(hdcCompatible,0,0,nScreenWidth, nScreenHeight, hdcScreen,0,0,SRCCOPY|CAPTUREBLT); 

    SelectObject(hdcCompatible, hOldBmp); // always select the previously selected object once done
    // Get the BITMAPINFO structure from the bitmap
    GetDIBits(hdcScreen, hBmp, 0, 0, NULL, &MyBMInfo, DIB_RGB_COLORS);

    // create the bitmap buffer
    char* lpPixels = new char[MyBMInfo.bmiHeader.biSizeImage];

    MyBMInfo.bmiHeader.biCompression = BI_RGB; 
    MyBMInfo.bmiHeader.biBitCount = 24;  

    // get the actual bitmap buffer
    GetDIBits(hdcScreen, hBmp, 0, MyBMInfo.bmiHeader.biHeight, (LPVOID)lpPixels, &MyBMInfo, DIB_RGB_COLORS);

    //Clean Up
    DeleteDC(hdcCompatible);
    ReleaseDC(GetDesktopWindow(), hdcScreen);
    DeleteDC(hdcScreen);
    DeleteObject(hBmp);
    //DeleteObject(hOldBmp);

    return lpPixels;
}
catch(char *p)
{
    return 0;
}

}

和 C#

        [DllImport("consoleapplication1.dll", CallingConvention = CallingConvention.Cdecl)]
    static extern IntPtr ScreenCap(ref int size);
                while(true)
            {
                int size = 0;
                IntPtr ptr = ScreenCap(ref size);
                byte[] result = new byte[size];
                Marshal.Copy(ptr, result, 0, size);
                Marshal.Release(ptr);
                ptr = IntPtr.Zero;
                MainWindow.Dispatcher.Invoke(new Action(
                () =>
                    {
                        System.Windows.Media.ImageSource ThumbnailImage = System.Windows.Media.Imaging.BitmapSource.Create(1920, 1080, 96, 96, System.Windows.Media.PixelFormats.Bgr24, null, result, 1920 * 3);
                        MainWindow.canvasMain.Background = new System.Windows.Media.ImageBrush(ThumbnailImage);
                        result = null;
                        GC.Collect();
                        GC.WaitForPendingFinalizers();
                    }
                ), null);
            }

不确定我现在面临的问题是否是由于这样做造成的，但我现在从 C++ dll 中得到了严重的内存泄漏。如果这是另一个问题，我需要创建一个新线程吗？

** 编辑 **

通过在 C++ dll 中创建一个新函数来删除返回的 char 数组来解决问题。可能不优雅，但它有效。

我要非常感谢 Filip，他的评论帮助我查看了各种地方并看到了其他东西。 Jdweng，你的 IntPtr 真是天赐良机。不确定我是如何设置 Jdweng 回答的。很想给你们俩颁奖。

Answer 1

如果有人正在寻找同样的东西，这就是对我有用的东西。我非常感谢 Filip Kocica 和 jdweng，他们的建议给了我一些想法并且帮助很大。非常感谢和赞赏。

C++

    char* lpPixels;
__declspec(dllexport) BOOL ScreenCapClean()
{
    delete[] lpPixels;
    return 1;
}

__declspec(dllexport) char* ScreenCap(DWORD * size)
{
    try
    {
        // Get screen dimensions
        int nScreenWidth = GetSystemMetrics(SM_CXSCREEN);
        int nScreenHeight = GetSystemMetrics(SM_CYSCREEN);

        *size = ((((24 * nScreenWidth + 31)&(~31)) / 8)*nScreenHeight);

        BITMAPINFO MyBMInfo = {0};
        MyBMInfo.bmiHeader.biSize = sizeof(MyBMInfo.bmiHeader);
        MyBMInfo.bmiHeader.biWidth = nScreenWidth;
        MyBMInfo.bmiHeader.biHeight = -nScreenHeight;
        MyBMInfo.bmiHeader.biPlanes = 1;
        MyBMInfo.bmiHeader.biBitCount = 24;
        MyBMInfo.bmiHeader.biCompression = BI_RGB;
        MyBMInfo.bmiHeader.biSizeImage = 0;
        MyBMInfo.bmiHeader.biXPelsPerMeter = 0;
        MyBMInfo.bmiHeader.biYPelsPerMeter = 0;
        MyBMInfo.bmiHeader.biClrUsed = 0;
        MyBMInfo.bmiHeader.biClrImportant = 0;

        // Create compatible DC, create a compatible bitmap and copy the screen using BitBlt()
        HDC hdcScreen = GetDC(0);
        HDC hdcCompatible  = CreateCompatibleDC(hdcScreen);
        HBITMAP hBmp = CreateCompatibleBitmap(hdcScreen, nScreenWidth, nScreenHeight);
        HGDIOBJ hOldBmp = (HGDIOBJ) SelectObject(hdcCompatible, hBmp);

        BOOL bOK = BitBlt(hdcCompatible,0,0,nScreenWidth, nScreenHeight, hdcScreen,0,0,SRCCOPY|CAPTUREBLT); 

        SelectObject(hdcCompatible, hOldBmp); // always select the previously selected object once done
        // Get the BITMAPINFO structure from the bitmap
        GetDIBits(hdcScreen, hBmp, 0, 0, NULL, &MyBMInfo, DIB_RGB_COLORS);

        // create the bitmap buffer
        lpPixels = new char[MyBMInfo.bmiHeader.biSizeImage];

        MyBMInfo.bmiHeader.biCompression = BI_RGB; 
        MyBMInfo.bmiHeader.biBitCount = 24;

        // get the actual bitmap buffer
        GetDIBits(hdcScreen, hBmp, 0, -MyBMInfo.bmiHeader.biHeight, (LPVOID)lpPixels, &MyBMInfo, DIB_RGB_COLORS);

        //Clean Up
        ReleaseDC(0, hdcScreen);
        ReleaseDC(0, hdcCompatible);
        DeleteDC(hdcCompatible);
        DeleteDC(hdcScreen);
        DeleteObject(hBmp);
        DeleteObject(hOldBmp);

        return lpPixels;
    }
    catch(char *p)
    {
        return 0;
    }
}

C#

    [DllImport("consoleapplication1.dll", CallingConvention = CallingConvention.Cdecl)]
    static extern IntPtr ScreenCap(ref int size);
    [DllImport("consoleapplication1.dll", CallingConvention = CallingConvention.Cdecl)]
    static extern bool ScreenCapClean();

    int size = 0;
    IntPtr ptr = ScreenCap(ref size);
    byte[] result = new byte[size];
    Marshal.Copy(ptr, result, 0, size);
    Marshal.Release(ptr);
    ptr = IntPtr.Zero;
    //After doing what's required with the byte array
    bool hr = ScreenCapClean();

BitBlt 转换为字节数组并从 C++ 解析为 C#

BitBlt convert to byte array and parse from c++ to c#

c#

c++

arrays

screenshot

bitblt