Knowledge Base Nr: 00313 blobbmotl.cpp - http://www.swe-kaiser.de

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MFC/OTL: read oracle BLOB and display as Bitmap
mit otl und mfc oracle blob-feld auslesen das eine bmp.datei enthält und anzeigen

  
//ACHTUNG: es werden keine paletten unterstützt!!! d.h. das Bitformat muss RGB => 24 bit sein!

### - blob-feld mit sql-developer füllen:
  - in data-tab für tabelle edit-value-dialog für blobfeld öffnen
  - image-checkbox für ansicht aktivieren und load-button drücken
  - in save-dialog(!!!) datei auswählen
  - bild wird noch nicht angezeigt / edit-value-dialog mit ok verlassen
  - commit-button drücken
  - erst jetzt kann das bild angezeigt werden

### bitmap klasse

class CBitmapObject : public CBaseObject
{
public:
    CBitmapObject();
    virtual ~CBitmapObject();
...
    virtual void OnDraw(CBaseView* pView, CDC* pDC);

    VOID* m_lpBits;           // bitmap pixels
    BITMAPINFO* m_lpBitsInfo; // bitmap header
};

CBitmapObject::CBitmapObject() : CBaseObject()
{
    m_lpBits = NULL;           // bitmap bits
    m_lpBitsInfo = NULL; // bitmap data
}

CBitmapObject::~CBitmapObject()
{
    if (m_lpBits)
        GlobalFree(m_lpBits);
    if (m_lpBitsInfo)
        GlobalFree(m_lpBitsInfo);
}

void CBitmapObject::OnDraw(CDC* pDC)
{
    if (!m_lpBitsInfo)
        return;

    ::StretchDIBits(pDC->m_hDC,       // handle to DC
                    x,                // x-coord of destination upper-left corner
                    y,                // y-coord of destination upper-left corner
                    w,                // width of destination rectangle
                    h,                // height of destination rectangle
                    0,                // x-coord of source upper-left corner
                    0,                // y-coord of source upper-left corner
                    ((*m_lpBitsInfo).bmiHeader).biWidth,   // width of source rectangle
                    ((*m_lpBitsInfo).bmiHeader).biHeight,  // height of source rectangle
                    m_lpBits,         // bitmap bits
                    m_lpBitsInfo,     // bitmap data
                    DIB_RGB_COLORS,   // usage options
                    SRCCOPY);         // raster operation code
}

### - blob-feld mit otl auslesen


### - bmp-datei (inhalt blob-feld) in CBitmap einlesen


void CHelperFunc::GetBitmapFromBlob(CBitmapObject* pBitmapObj, void* lpFileData)
{
    int nFileHeaderSize = sizeof(BITMAPFILEHEADER);

    LPBITMAPINFOHEADER bmih = (LPBITMAPINFOHEADER) ((LPBYTE)lpFileData + nFileHeaderSize);
    if ((*bmih).biBitCount != 24)
    {
        AfxMessageBox(theApp.Translate(L"Bitmap hat falsches Format (biBitCount != 24)!"), MB_OK|MB_ICONEXCLAMATION);
        return;
    }

    LPBITMAPINFOHEADER lpBitmap = bmih;

    //get pointers into bitmap structures (header, color table and picture bits)
    LPBITMAPINFO pBitmapInfo = (LPBITMAPINFO)lpBitmap;
    LPBITMAPINFOHEADER pBitmapInfoHeader = (LPBITMAPINFOHEADER)lpBitmap;

    //if the picture data uses more then 8 bits per pixel, there's
    //no color table to turn into a palette
    int nNumberOfColors = 0;

    LPBYTE pBitmapPictureData = (LPBYTE)lpFileData + lpBitmap->biSize + nFileHeaderSize + nNumberOfColors*sizeof(RGBQUAD);

    //create device independant bitmap
    CDC dcScreen;
    dcScreen.Attach(::GetDC(NULL));

    HBITMAP bitmap = ::CreateDIBitmap(dcScreen.m_hDC, pBitmapInfoHeader, CBM_INIT, pBitmapPictureData,
        pBitmapInfo, DIB_RGB_COLORS);
    ASSERT(bitmap);

    if (pBitmapObj->m_lpBits)
        GlobalFree(pBitmapObj->m_lpBits);
    if (pBitmapObj->m_lpBitsInfo)
        GlobalFree(pBitmapObj->m_lpBitsInfo);

    int nSize = pBitmapInfoHeader->biSizeImage;
    pBitmapObj->m_lpBits = (VOID*) GlobalAlloc(GMEM_FIXED, nSize);
    CopyMemory(pBitmapObj->m_lpBits, pBitmapPictureData, nSize);

    nSize = pBitmapInfoHeader->biSize*2;
    pBitmapObj->m_lpBitsInfo = (BITMAPINFO*)GlobalAlloc(GMEM_FIXED, nSize);
    CopyMemory(pBitmapObj->m_lpBitsInfo, pBitmapInfo, nSize);

    int cx = pBitmapInfoHeader->biWidth*6.5f;
    int cy = cx * ((float)pBitmapInfoHeader->biHeight / pBitmapInfoHeader->biWidth);
    pBitmapObj->SetSize(CSize(cx, cy));

    ::ReleaseDC(NULL, dcScreen.Detach());
}