CODEWITHSUNDEEP
c++stringdatetime
BigBlackBunny
BigBlackBunny

Reputation: 77

c++: Converting DateTime To Be Used As A File Name

I'm working on a screen capture method for my program. For each screen capture, I'm trying to have the image named based on the DateTime down to the second. Right now, everything would be named screen.jpg.

How can I change "screen" to the current DateTime?

I've tried playing around with the line that names it, but I just keep getting errors such as "expression must have integral or unscoped enum type." I'm not sure what that means.

void BitmapToJpg(HBITMAP hbmpImage, int width, int height)
{
    time_t now = time(0);
    char* dt = ctime(&now);

    Bitmap *p_bmp = Bitmap::FromHBITMAP(hbmpImage, NULL);
    //Bitmap *p_bmp = new Bitmap(width, height, PixelFormat32bppARGB);

    CLSID pngClsid;
    int result = GetEncoderClsid(L"image/jpeg", &pngClsid);
    if (result != -1)
        std::cout << "Encoder succeeded" << std::endl;
    else
        std::cout << "Encoder failed" << std::endl;
    p_bmp->Save(L"screen_.jpg", &pngClsid, NULL);
    delete p_bmp;
}

UPDATE:

This version hasn't given me any errors, so I'm going to try to use it. I'll update this post to verify if it worked properly or not when my program attempts to use it! :)

Revised code:

void BitmapToJpg(HBITMAP hbmpImage, int width, int height)
{
    time_t now = time(0);
    char* dt = ctime(&now);

    std::wstring_convert<std::codecvt_utf8_utf16<wchar_t>> converter;
    std::wstring wide = converter.from_bytes(dt);


    Bitmap *p_bmp = Bitmap::FromHBITMAP(hbmpImage, NULL);
    //Bitmap *p_bmp = new Bitmap(width, height, PixelFormat32bppARGB);

    CLSID pngClsid;
    int result = GetEncoderClsid(L"image/jpeg", &pngClsid);
    if (result != -1)
        std::cout << "Encoder succeeded" << std::endl;
    else
        std::cout << "Encoder failed" << std::endl;
    std::wstring fileName = std::wstring(L"screen_") + wide + (L".jpg");
    p_bmp->Save(fileName.c_str(), &pngClsid, NULL);
    delete p_bmp;
}

Upvotes: 0

Views: 168

Answers (1)

iehrlich
iehrlich

Reputation: 3592

You're actually almost there. However, one more thing needs to be done in order to get this working. As of the latest edit of the code, you pass the first parameter of Bitmap::Save (and, inherently, Image::Save) of type std::wstring, the latter being a typedef for std::basic_string<wchar_t>. However the method requires its first parameter to be WCHAR *. So, all you need to do, is to re-write problematic lines as follows:

std::wstring fileName = std::wstring(L"screen_") + wide + L(".jpg");
p_bmp->Save(fileName.c_str(), &pngClsid, NULL);

This should do the trick.

The reason of the problem is, std::basic_string<CharT> can't be converted to CharT* implicitly, and there is a specific interface for such conversion, namely std::basic_string<CharT>::c_str().

Upvotes: 3

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