Question

我正在使用Visual Studio 2017，我编写了代码来创建一个文件夹，并在按下鼠标按钮时捕获屏幕截图并将屏幕截图保存到.bmp文件。但是我不知道为什么该脚本不起作用。 Visual Studio可以编译它而不会出现错误/警告。

代码如下：

    // variable to store the HANDLE to the hook. Don't declare it anywhere else then globally
    // or you will get problems since every function uses this variable.
    HHOOK _hook;

    // This struct contains the data received by the hook callback. As you see in the callback function
    // it contains the thing you will need: vkCode = virtual key code.
    KBDLLHOOKSTRUCT kbdStruct;

    int filenum = 1;
    // This is the callback function. Consider it the event that is raised when, in this case, 
    // a key is pressed.
void TakeScreenShot(const char* filename)
{
    //keybd_event(VK_SNAPSHOT, 0x45, KEYEVENTF_EXTENDEDKEY, 0);
    //keybd_event(VK_SNAPSHOT, 0x45, KEYEVENTF_EXTENDEDKEY | KEYEVENTF_KEYUP, 0);
    HBITMAP h;

    POINT a, b;
    a.x = 0;
    a.y = 0;

    b.x = GetSystemMetrics(SM_CXSCREEN);
    b.y = GetSystemMetrics(SM_CYSCREEN);

    HDC     hScreen = GetDC(NULL);
    HDC     hDC = CreateCompatibleDC(hScreen);
    HBITMAP hBitmap = CreateCompatibleBitmap(hScreen, abs(b.x - a.x), abs(b.y - a.y));
    HGDIOBJ old_obj = SelectObject(hDC, hBitmap);
    BOOL    bRet = BitBlt(hDC, 0, 0, abs(b.x - a.x), abs(b.y - a.y), hScreen, a.x, a.y, SRCCOPY);


    // save bitmap to clipboard
    OpenClipboard(NULL);
    EmptyClipboard();
    SetClipboardData(CF_BITMAP, hBitmap);
    CloseClipboard();

    // clean up
    SelectObject(hDC, old_obj);
    DeleteDC(hDC);
    ReleaseDC(NULL, hScreen);
    DeleteObject(hBitmap);

    OpenClipboard(NULL);
    h = (HBITMAP)GetClipboardData(CF_BITMAP);
    CloseClipboard();
    HDC hdc = NULL;
    FILE*fp = NULL;
    LPVOID pBuf = NULL;
    BITMAPINFO bmpInfo;
    BITMAPFILEHEADER bmpFileHeader;
    do
    {
        hdc = GetDC(NULL);
        ZeroMemory(&bmpInfo, sizeof(BITMAPINFO));
        bmpInfo.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
        GetDIBits(hdc, h, 0, 0, NULL, &bmpInfo, DIB_RGB_COLORS);
        if (bmpInfo.bmiHeader.biSizeImage <= 0)
            bmpInfo.bmiHeader.biSizeImage = bmpInfo.bmiHeader.biWidth*abs(bmpInfo.bmiHeader.biHeight)*(bmpInfo.bmiHeader.biBitCount + 7) / 8;
        if ((pBuf = malloc(bmpInfo.bmiHeader.biSizeImage)) == NULL)
        {
            MessageBox(NULL, TEXT("Unable to Allocate Bitmap Memory"), TEXT("Error"), MB_OK | MB_ICONERROR);
            break;
        }
        bmpInfo.bmiHeader.biCompression = BI_RGB;
        GetDIBits(hdc, h, 0, bmpInfo.bmiHeader.biHeight, pBuf, &bmpInfo, DIB_RGB_COLORS);
        if ((fp = fopen(filename, "wb")) == NULL)
        {
            MessageBox(NULL, TEXT("Unable to Create Bitmap File"), TEXT("Error"), MB_OK | MB_ICONERROR);
            break;
        }
        bmpFileHeader.bfReserved1 = 0;
        bmpFileHeader.bfReserved2 = 0;
        bmpFileHeader.bfSize = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER) + bmpInfo.bmiHeader.biSizeImage;
        bmpFileHeader.bfType = 'MB';
        bmpFileHeader.bfOffBits = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);
        fwrite(&bmpFileHeader, sizeof(BITMAPFILEHEADER), 1, fp);
        fwrite(&bmpInfo.bmiHeader, sizeof(BITMAPINFOHEADER), 1, fp);
        fwrite(pBuf, bmpInfo.bmiHeader.biSizeImage, 1, fp);
    }

    while (false);
    if (hdc)ReleaseDC(NULL, hdc);
    if (pBuf) free(pBuf);
    if (fp)fclose(fp);
}

LRESULT __stdcall HookCallback(int nCode, WPARAM wParam, LPARAM lParam)
{
    if (nCode >= 0)
    {
        // the action is valid: HC_ACTION.
        if (wParam == WM_LBUTTONDOWN)
        {
            std::string OutputFolder = "C:\\temp";
            std::string filename = "ss";
            if (CreateDirectory(OutputFolder.c_str(), NULL) ||
                ERROR_ALREADY_EXISTS == GetLastError())
            {

            }
            else
            {
                // Failed to create directory.
            }
            auto numfile = std::to_string(filenum);
            TakeScreenShot((OutputFolder + "\\" + filename + std::to_string(filenum) + ".bmp").c_str());
            filenum++;
        }
    }

    // call the next hook in the hook chain. This is nessecary or your hook chain will break and the hook stops
    return CallNextHookEx(_hook, nCode, wParam, lParam);
}



void ReleaseHook()
{
    UnhookWindowsHookEx(_hook);
}


int main()
{
    // Don't mind this, it is a meaningless loop to keep a console application running.
    // I used this to test the keyboard hook functionality. If you want to test it, keep it in ;)
    MSG msg;
    while (GetMessage(&msg, NULL, 0, 0))
    {

    }
}

如果单击它，将不会创建目录（如果它不存在），并且不会创建.bmp文件。

Answer 1

正如其他人所说，您永远不会安装钩子！另外，从我的测试中可以看出，您需要将消息分发到某种形式的窗口中才能调用WH_MOUSE挂钩。

以下是对我有用的main ()的最低版本：

int main()
{
    _hook = SetWindowsHookEx (WH_MOUSE, HookCallback, NULL, GetCurrentThreadId ());
    if (_hook == NULL)
        ...
    MessageBox (NULL, "Click OK to quit", "Screen Grabber", MB_OK);
    UnhookWindowsHookEx (_hook);
}

然后，其余代码也可以正常工作，尽管就像其他人所说的那样有些混乱。

但是，这只会在消息框内捕获鼠标单击，我认为这不是您想要的。

如果要全局捕获它们，则需要安装“低级”鼠标钩。这需要是一个全局钩子，否则代码看起来几乎相同。安装和运行挂钩的代码是：

int main()
{
    _hook = SetWindowsHookEx (WH_MOUSE_LL, HookCallback, NULL, 0);
    MSG msg;
    while (GetMessage (&msg, NULL, 0, 0))
        DispatchMessage (&msg);
    UnhookWindowsHookEx(_hook);
}

单击鼠标时的C ++屏幕截图不起作用

1 个答案: