VC在Sql Server数据库中如何存取二进制图片信息

转载地址：VC在Sql Server数据库中如何存取二进制图片信息  http://blog.hehehehehe.cn/a/1396.htm

在VC6.0中我们通常用Ado的Field 对象的GetChuck和AppendChunk来读写Blob对象，但是这样做要写很多的代码，其实ado给我们提供了一个更易操作的对象那就是 Stream Object，通过它我们可以更容易的操作数据库中的Blob对象，而且可以直接把Blob对象从数据库保存到本地文件，或者直接读取文件写入到数据库 中。下面就详细描述如何操作。[喝小酒的网摘]http://blog.hehehehehe.cn/a/1396.htm
首先申明Stream对象
_ StreamPtr pStm;
pStm.CreateInstance( "ADODB.Stream");
variant_t varOptional(DISP_E_PARAMNOTFOUND,VT_ERROR);
pStm- >PutType(adTypeBinary);//类型为二进制
//得到字段内容的大小
long lDataSize = m_pRecordset- >GetFields()->GetItem("photo")->ActualSize;
//m_pRecordset为一个打开的纪录集对象，含有photo这个blob字段
pStm- >Open( varOptional,
adModeUnknown, adOpenStreamUnspecified, _bstr_t(), _bstr_t());
//打开pStm
pStm- >Write(_variant_t(m_pRecordset->GetFields()->GetItem("photo")->Value));
//把photo字段的内容写入pStm
pStm- >SaveToFile("c:\publogo.jpg", adSaveCreateOverWrite);
pStm- >Close();
//直接保存为文件,如果是别的格式只要保存的时候改变后缀就可以了
下面是如果不保存成文件可以直接通过Com对象来绘制该图片，IPicture 可以显示多种格式图片.
HGLOBAL hGlobal = GlobalAlloc(GMEM_MOVEABLE, pStm- >GetSize());
LPVOID pvData = NULL;
IStream *ps;
if (hGlobal != NULL)
{
if ((pvData = GlobalLock(hGlobal)) != NULL)
{
char * m_pBMPBuffer = new char[pStm- >GetSize()+1];//分配必要的存储空间
char *pBuf = NULL;
SafeArrayAccessData(varBLOB.parray,(void **) &pBuf);
memcpy(pvData,pBuf,pStm- >GetSize()); //复制数据到缓冲 区 m_pBMPBuffer
SafeArrayUnaccessData (varBLOB.parray);
GlobalUnlock(hGlobal);
CreateStreamOnHGlobal(hGlobal, TRUE, &ps);
}
}

IPicture *pPic;
if(SUCCEEDED(OleLoadPicture(ps,pStm- >GetSize() ,TRUE,IID_IPicture,(LPVOID*)&pPic)))
{

OLE_XSIZE_HIMETRIC hmWidth;
OLE_YSIZE_HIMETRIC hmHeight;
pPic- >get_Width(&hmWidth);
pPic- >get_Height(&hmHeight);
double fX,fY;
CDC *pDC = GetClientDC();//这里根据具体请况来取
fX=(double)pDC- >GetDeviceCaps(HORZRES)*(double)hmWidth/((double)pDC->GetDeviceCaps(HORZSIZE)*100.0);
fY =(double)pDC- >GetDeviceCaps(VERTRES)*(double)hmHeight/((double)pDC->GetDeviceCaps(VERTSIZE)*100.0);
if(FAILED(pPic- >Render(*pDC,0,0,(DWORD)fX,(DWORD)fY,0,hmHeight,hmWidth,-hmHeight,NULL)))
AfxMessageBox( "图像绘制失败！");
pPic- >Release();
}
这样就完成了对图片文件从数据库读出和显示的过程。
对于从文件写入数据库就相对的容易多了,
_StreamPtr pStm;
pStm.CreateInstance( "ADODB.Stream");
variant_t varOptional(DISP_E_PARAMNOTFOUND,VT_ERROR);
long lDataSize = m_pRecordset- >GetFields()->GetItem("photo")->ActualSize;
pStm- >PutType(adTypeBinary;

pStm- >Open( varOptional,
adModeUnknown, adOpenStreamUnspecified, _bstr_t(), _bstr_t());
pStm- >LoadFromFile("c:\book.gif");//读入文件
variant_t varBLOB=pStm- >Read(adReadAll);
m_pRecordset- >GetFields()->GetItem("photo")->Value= varBLOB;//保存到数据集对象。
以上就是关于ADO的Stream对象操作数据库中的blob字段的具体方法，主要是对图片我们还可对它进行改造成其他的，比如读者可以改造成读取XMl文件，并保存等等。
void CDlsjzDlg::ReadData()
{
if(m_pRecordset- >adoEOF m_pRecordset->BOF)
{
m_name.Empty();
m_ghao.Empty();
UpdateData(FALSE);
return;
}
char *m_pBMPBuffer1;
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_pBMPBuffer1 = new char[lDataSize+1]) {
char *pBuf = NULL;
SafeArrayAccessData(varBLOB.parray,(void **) &pBuf);
memcpy(m_pBMPBuffer1,pBuf,lDataSize);
SafeArrayUnaccessData (varBLOB.parray);
m_nFileLen = lDataSize;
Picture.Load((BYTE *)m_pBMPBuffer1,lDataSize);
m_Display.SetBitmap((HBITMAP)Picture.GetSafeHandle());
}
}
}
else
{
Picture.Load(IDB_BITMAP1, "BMP");
m_Display.SetBitmap((HBITMAP)Picture.GetSafeHandle());
}
m_name=m_pRecordset- >GetCollect(_variant_t("syz")).bstrVal;
if(m_name <='0') m_name=_T("");
m_ghao=m_pRecordset- >GetCollect(_variant_t("gonghao")).bstrVal;
if(m_ghao <'0') m_ghao=_T("");
m_ddd=m_pRecordset- >GetCollect(_variant_t("jcdata"));
m_ddd.vt=VT_DATE;
m_jcdate.SetValue(m_ddd);
m_ddd=m_pRecordset- >GetCollect(_variant_t("sjdata"));
m_ddd.vt=VT_DATE;
m_sjdate.SetValue(m_ddd);
m_jqbh.Format( "%d",m_pRecordset->GetCollect(_variant_t("jqbh")).intVal);
if(m_jqbh=='0')
m_jqbh= "公用";
else
m_jqbh=m_jqbh+ "號工作站";
m_pBMPBuffer1=NULL;
UpdateData(FALSE);
}
void CDlsjzDlg::Save()
{
UpdateData();
char *pBuf = m_pBMPBuffer;
VARIANT varBLOB;
SAFEARRAY *psa;
SAFEARRAYBOUND rgsabound[1];
m_pRecordset- >PutCollect("syz",_variant_t(m_name));
m_pRecordset- >PutCollect("jqbh",atol(m_jqbh));
m_pRecordset- >PutCollect("gonghao",_variant_t(m_ghao));
m_pRecordset- >PutCollect("jcdata",m_jcdate.GetValue());
m_pRecordset- >PutCollect("sjdata",m_sjdate.GetValue());
if(pBuf)
{
rgsabound[0].lLbound = 0;
rgsabound[0].cElements = m_nFileLen;
psa = SafeArrayCreate(VT_UI1, 1, rgsabound);
for (long i = 0; i < (long)m_nFileLen; i++)
SafeArrayPutElement (psa, &i, pBuf++);
varBLOB.vt = VT_ARRAY | VT_UI1;
varBLOB.parray = psa;
m_pRecordset- >GetFields()->GetItem("photo")->AppendChunk(varBLOB);
}
m_pBMPBuffer=NULL;
m_pRecordset- >Update();
} [喝小酒的网摘]http://blog.hehehehehe.cn/a/1396.htm