VC保存和显示数据库图像(BMP)

源代码:下载

简述关键代码如下：

1、保存图片数据到数据库

//BMP图片保存到数据库
    try
    {
        _RecordsetPtr    pRecordset;
        pRecordset.CreateInstance(__uuidof(Recordset));
        pRecordset->Open("SELECT * FROM bmp",_variant_t((IDispatch*)pConnection),adOpenStatic,adLockOptimistic,adCmdText);
        pRecordset->AddNew();
        pRecordset->Fields->Item["bmpid"]->Value = (_variant_t)m_BMPId;        //bmpid
        VARIANT pvList;
        SetPictureToVariant(pvList,(unsigned char *)m_pBMPBuffer);
        pRecordset->Fields->Item["bmpimage"]->AppendChunk(pvList);            //BMP图像文件
        VariantClear(&pvList);
    
        pRecordset->Update();
        pRecordset->Close();
        AfxMessageBox("BMP图像保存成功！");
    }
    catch(...)
    {
        AfxMessageBox("数据库读取失败");
        return;
    }
其中SetPictureToVariant如下：
    void CBMPinDBDlg::SetPictureToVariant(VARIANT &pvList, unsigned char *sPicture)
    {
        SAFEARRAYBOUND saBound[1];
        saBound[0].cElements = m_nFileLen;
        saBound[0].lLbound = 0;
        SAFEARRAY *pSA = SafeArrayCreate(VT_UI1, 1, saBound);    
        for (long l = 0; l < (long)m_nFileLen; l ++)
        {
            SafeArrayPutElement( pSA, &l, (void*)&sPicture[l]);        
        }
        VariantClear(&pvList);
        pvList.vt = VT_UI1 | VT_ARRAY;
        pvList.parray = pSA;
    }

2、从数据库读取图像文件并且显示在界面

    //从数据库里取BMP图像文件
    try
    {
        _RecordsetPtr    pRecordset;
        char sSql[129];
        sprintf(sSql,"SELECT *FROM bmp WHERE bmpid='%s'",m_BMPId);
        pRecordset.CreateInstance(__uuidof(Recordset));
        pRecordset->Open(sSql,_variant_t((IDispatch*)pConnection),adOpenStatic,adLockOptimistic,adCmdText);
        if (pRecordset->adoEOF)
        {
            CString str;
            str.Format("没有BMPid为: %s 的BMP图像!",m_BMPId );
            AfxMessageBox(str);
            DestroyPhoto();
            Invalidate();
            m_BMPId = "";
            UpdateData(false);
            m_EidtBMPId.SetFocus();
            return;
        }
        _variant_t pvList ;        
        long lDataSize = pRecordset->GetFields()->GetItem("bmpimage")->ActualSize;
        m_nFileLen = (DWORD)lDataSize;
        if(lDataSize > 0)
        {
            _variant_t            varBLOB;
            varBLOB = pRecordset->GetFields()->GetItem("bmpimage")->GetChunk(lDataSize);
            //把二进制格式的图片转为图片格式
            if(varBLOB.vt == (VT_ARRAY | VT_UI1))
            {
                if(m_pBMPBuffer = new char[lDataSize+1])        
                {    
                    char *pBuf = NULL;
                    SafeArrayAccessData(varBLOB.parray,(void **)&pBuf);
                    memcpy(m_pBMPBuffer,pBuf,lDataSize);                
                    SafeArrayUnaccessData (varBLOB.parray);
                    m_nFileLen = lDataSize;
                    m_hBitmap = BufferToHBITMAP();
                    Invalidate();//在界面显示                
                }
            }
        }
        
    }
    catch(...)
    {
        AfxMessageBox("数据库读取失败");
        return;
    }

上次写了两篇关于在VC界面显示图片(BMP、JPG)的文章，但是并没有涉及到数据库，所以这次补写了这两篇有关数据库的文章，这两篇文章用的是access的数据库，其它的数据库操作道理是一样的。

具体的程序请参考附带的例子，例子里面有详细的注释。