Re: Load JPEG from file

From: Crispen, Bob (bob.crispen_at_boeing.com)
Date: 27 February 2003

Subject: Re: Load JPEG from file
Date: Fri, 14 Feb 2003 12:16:52 +0100
From: Lucian Wischik <lu.nn_at_wischik.com> Organization: University of Bologna
Newsgroups: comp.os.ms-windows.programmer.win32

Chris <dhira_at_softhome.net> wrote:
>Can someone help me with an example of how I load a JPEG from a file >and draws it on the DC in pure Windows API?

Look up OleLoadPicture and OleLoadPicturePath. They load JPEGs and are present in all versions of Windows. Well, that's what I read recently, but I haven't yet had time to do it myself. Here's the code sample I picked up:

void LoadDibFromFile(LPCTSTR szFile, CDib *pCDib) {

// open file

        HANDLE hFile = CreateFile(szFile, GENERIC_READ, 0, NULL, OPEN_EXISTING, 0, NULL);
        _ASSERTE(INVALID_HANDLE_VALUE != hFile);



        // get file size

        DWORD dwFileSize = GetFileSize(hFile, NULL);
        _ASSERTE(-1 != dwFileSize);

        LPVOID pvData = NULL;


        // alloc memory based on file size

        HGLOBAL hGlobal = GlobalAlloc(GMEM_MOVEABLE, dwFileSize);
        _ASSERTE(NULL != hGlobal);

        pvData = GlobalLock(hGlobal);
        _ASSERTE(NULL != pvData);

        DWORD dwBytesRead = 0;


        // read file and store in global memory

        BOOL bRead = ReadFile(hFile, pvData, dwFileSize, &dwBytesRead, NULL);
        _ASSERTE(FALSE != bRead);
        GlobalUnlock(hGlobal);
        CloseHandle(hFile);

        LPSTREAM pstm = NULL;


        // create IStream* from global memory

        HRESULT hr = CreateStreamOnHGlobal(hGlobal, TRUE, &pstm);
        _ASSERTE(SUCCEEDED(hr) && pstm);



        // Create IPicture from image file

        LPPICTURE pPicture;
        hr = ::OleLoadPicture(pstm, dwFileSize, FALSE, IID_IPicture, (LPVOID
*)&pPicture);
        _ASSERTE(SUCCEEDED(hr) && pPicture);
        pstm->Release();



        // get the bitmap handle

        HBITMAP hBitmap;
        if (S_OK != pPicture->get_Handle((OLE_HANDLE FAR *) &hBitmap))
        {
                TRACE("Couldn't get bitmap handle from picture\n");
                ASSERT(FALSE);
        }



        // create a memory DC for the bitmap

        HDC memDC = CreateCompatibleDC(NULL);
        HBITMAP oldBitmap;
        oldBitmap = (HBITMAP) SelectObject(memDC, hBitmap);



        // find the size of the DIB to be created

        BITMAPINFO bInfo;
        ZeroMemory(&bInfo, sizeof(bInfo));
        bInfo.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
        bInfo.bmiHeader.biBitCount = 0;

        if (!GetDIBits(memDC, hBitmap, 0, 0, NULL, &bInfo, DIB_RGB_COLORS))
        {
                DWORD error = GetLastError();
                ASSERT(FALSE);
        }

        int totalSize = PackedDibGetInfoHeaderSize(&bInfo) +
            PackedDibGetColorTableSize(&bInfo) +
            PackedDibGetBitsSize(&bInfo);



        // allocate and create a packed DIB

        LPBITMAPINFO packedBitmap = (LPBITMAPINFO) new BYTE[totalSize];
        CopyMemory(packedBitmap, &bInfo, sizeof(BITMAPINFO));

        if (!GetDIBits(
                memDC,
                hBitmap,
                0,
                PackedDibGetHeight(&bInfo),
                (void *) (((BYTE *) packedBitmap) +
                                  PackedDibGetInfoHeaderSize(&bInfo) +
                                  PackedDibGetColorTableSize(&bInfo)),
                packedBitmap,
                DIB_RGB_COLORS))
        {
                DWORD error = GetLastError();
                ASSERT(FALSE);
        }



        // attach the packed DIB to the CDib object.  The object is now responsible

        // for deletion (it should do this in the destructor)

        pCDib->AttachMemory((LPVOID) packedBitmap, TRUE);



        // clean up the memory DC

        SelectObject(memDC, oldBitmap);
        DeleteDC(memDC);

} 
--
Lucian

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