怎样读取ACCESS中的图片_access varblob-优快云博客

本文介绍使用ADO从数据库中读取BMP图像数据的方法，包括获取图像大小、读取图像块并转换为HBITMAP的过程。

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用ADO:

void CADOBlobDlg::ReadData()
{
//DestroyPhoto(); ///清除原图像
if(m_pRecordset->adoEOF||m_pRecordset->BOF)
{
m_UserName.Empty();
m_Old.Empty();
UpdateData(FALSE);
return;
}
long lDataSize = m_pRecordset->GetFields()->GetItem("photo")->ActualSize;
if(lDataSize > 0)
{
_variant_t varBLOB;
varBLOB = m_pRecordset->GetFields()->GetItem("photo")->GetChunk(lDataSize);
if(varBLOB.vt == (VT_ARRAY | VT_UI1))
{
if(m_pBMPBuffer = new char[lDataSize+1]) ///重新分配必要的存储空间
{
char *pBuf = NULL;
SafeArrayAccessData(varBLOB.parray,(void **)&pBuf);
memcpy(m_pBMPBuffer,pBuf,lDataSize); ///复制数据到缓冲区m_pBMPBuffer
SafeArrayUnaccessData (varBLOB.parray);
m_nFileLen = lDataSize;
m_hPhotoBitmap = BufferToHBITMAP(); ///生成BITMAP对象
}
}
}
m_UserName = m_pRecordset->GetCollect("username").bstrVal;
m_Old.Format("%d",m_pRecordset->GetCollect("old").lVal);
m_editUserName.EnableWindow();
m_editOld.EnableWindow();
m_buttonSelectPhoto.EnableWindow();
m_buttonDeleteUser.EnableWindow();
UpdateData(FALSE);
}

///////////将内存中的BMP文件内容转换到HBITMAP///////
HBITMAP CADOBlobDlg::BufferToHBITMAP()
{
HBITMAP hBmp;
LPSTR hDIB,lpBuffer = m_pBMPBuffer;
LPVOID lpDIBBits;
BITMAPFILEHEADER bmfHeader;
DWORD bmfHeaderLen;

bmfHeaderLen = sizeof(bmfHeader);
strncpy((LPSTR)&bmfHeader,(LPSTR)lpBuffer,bmfHeaderLen);
if (bmfHeader.bfType != ((WORD) ('M' << 8) | 'B')) return NULL;
hDIB = lpBuffer + bmfHeaderLen;
BITMAPINFOHEADER &bmiHeader = *(LPBITMAPINFOHEADER)hDIB ;
BITMAPINFO &bmInfo = *(LPBITMAPINFO)hDIB ;
int nColors = bmiHeader.biClrUsed ? bmiHeader.biClrUsed : 1 << bmiHeader.biBitCount;
if( bmInfo.bmiHeader.biBitCount > 8 )
lpDIBBits = (LPVOID)((LPDWORD)(bmInfo.bmiColors + bmInfo.bmiHeader.biClrUsed) +
((bmInfo.bmiHeader.biCompression == BI_BITFIELDS) ? 3 : 0));
else
lpDIBBits = (LPVOID)(bmInfo.bmiColors + nColors);
CClientDC dc(this);
hBmp = CreateDIBitmap(dc.m_hDC,&bmiHeader,CBM_INIT,lpDIBBits,&bmInfo,DIB_RGB_COLORS);
return hBmp;
}