C++使用ADO实现存取图片的方法

//导入ADO
#import "C:\Program Files\Common Files\System\ado\msado15.dll"\
rename_namespace("ADOCG")rename("EOF","EndOfFile")
using namespace ADOCG;

BOOL OpenConnection()
{
if(m_pConn == NULL)
{
m_pConn.CreateInstance("ADODB.Connection"); //创建_ConnectionPtr的一个实例
}

try
{
if(adStateClosed == m_pConn->State) //如果已关闭
{
m_pConn->Open("driver={SQL Server};Server=HP-CADD722B76A0;DATABASE=TestImage;UID=sa;PWD=sa","","",adModeUnknown); //因数据库而异
return true;
}
}
catch(_com_error e)
{
AfxMessageBox(_T("连接数据库失败!"));
return false;
}
}

m_pRecord.CreateInstance( __uuidof(RecordSet) );

CString strSQL;
//获取表中最大的id，下一次插入时就用id+1
strSQL.Format(_T("Select count(*) as num, Max(ID) as maxid from Images"));
try
{
m_pRecord->Open(strSQL.AllocSysString(), m_pConn.GetInterfacePtr(),
adOpenDynamic, adLockUnspecified, adCmdText);
}
catch (_com_error e)
{
AfxMessageBox(_T("读取最大的id异常"));
eturn;
}

//从RecordSet中获取数据数目和当前数据库中最大的ID。
int num = m_pRecord->GetCollect("num");
int maxid;
if (num != 0)
{
maxid = m_pRecord->GetCollect("maxid");
}
else
{
maxid = 0;
}

strSQL.Format(_T("Select * from Images where ID = %d"), maxid);
//下面向数据库中插入图片等。
//首先从数据库中读id最大的那条数据，主要目的是为了将RecordSet初始化
m_pRecord.CreateInstance(__uuidof(Recordset));

m_pRecord->Open(strSQL.AllocSysString(), m_pConn.GetInterfacePtr(), 
adOpenDynamic, adLockOptimistic, adCmdText); //这是AddNew方法要求的

CString imagepath = _T("F:/200713454/20090326.bmp");
CString imagename = imagepath.Right(12);
try
{
m_pRecord->AddNew(); //为记录集添加新的一行，更新时就会把这条新纪录放到数据库中
}
catch (_com_error e) 
{
AfxMessageBox(_T("不能插入一条新的记录"));
return;
}

try
{

//使用putcollect插入非图像数据，使用SetImage2DB插入图像数据
m_pRecord->PutCollect("ID", _variant_t(maxid+1));
m_pRecord->PutCollect("Name", _variant_t(imagename));
SetImage2DB(imagepath);
}
catch (_com_error e)
{
AfxMessageBox(_T("插入图片有异常"));
return;
}
m_pRecord->Update();

//使用完毕，关闭m_pRecord，并设置为NULL，最后关闭数据库连接
m_pRecord->Close();
m_pRecord = NULL;
CloseConnection();

#include <GdiPlus.h>
using namespace Gdiplus;

GdiplusStartupInput m_gdiplusstartUpInput;
ULONG_PTR m_GdiplusToken;

GdiplusStartup(&m_GdiplusToken, &m_gdiplusstartUpInput, NULL);

GdiplusShutdown(m_GdiplusToken);

OpenConnection();

m_pRecord.CreateInstance(__uuidof(Recordset));
CString strSQL;
strSQL.Format(_T("Select * from Images where ID = 1"));
try
{
m_pRecord->Open(strSQL.AllocSysString(), m_pConn.GetInterfacePtr(),
adOpenDynamic, adLockOptimistic, adCmdText);
}
catch (_com_error e)
{
AfxMessageBox(_T("读取图片信息异常"));
return;
}

LPVOID Data;
char* pbuf = NULL;

long lDatasize = m_pRecord->GetFields()->GetItem("ImageData")->ActualSize; //数据库中图像数据长度
CString imagename = m_pRecord->GetCollect("Name").bstrVal;
if (lDatasize > 0)
{
_variant_t varBLOB;
varBLOB = m_pRecord->GetFields()->GetItem("ImageData")->GetChunk(lDatasize);
Data = new char[lDatasize+1];
if (varBLOB.vt == (VT_ARRAY|VT_UI1))
{
SafeArrayAccessData(varBLOB.parray, (void **)&pbuf);
memcpy(Data, pbuf, lDatasize);
SafeArrayUnaccessData(varBLOB.parray);
}
}
IStream* pStm;
LONGLONG cb = lDatasize;
HGLOBAL hGlobal = GlobalAlloc(GMEM_MOVEABLE, cb);
LPVOID pvData;
if (hGlobal != NULL)
{
pvData = GlobalLock(hGlobal);
memcpy(pvData, Data, cb);
GlobalUnlock(hGlobal);
CreateStreamOnHGlobal(hGlobal, TRUE, &pStm);
}
else
{
AfxMessageBox(_T("Error"));
return;
}

CLSID encoderClsid;
GetEncoderClsid(L"image/bmp",&encoderClsid); //确定编码格式是bmp格式
Image image(pStm, TRUE);
CString imagepath;
imagepath.Format(_T("F:/200713454/%s"), imagename);
image.Save(imagepath, &encoderClsid, NULL); //把image中的数据按照bmp编码格式存到本地

m_pRecord->Close();
m_pRecord = NULL;
CloseConnection();

void CDlgTest::SetImage2DB(CString path)
{
VARIANT varChunk;
SAFEARRAY* psa;
SAFEARRAYBOUND rgsabound[1];
CFile f(path.operator LPCTSTR(),CFile::modeRead);
BYTE bval[ChunkSize+1];
long uIsRead=0;
while (1)
{
uIsRead=f.Read(bval,ChunkSize);
if (uIsRead==0) break;
rgsabound[0].cElements=uIsRead;
rgsabound[0].lLbound=0;
psa=SafeArrayCreate(VT_UI1,1,rgsabound);
for (long index=0;index<uIsRead;index++)
{
if (FAILED(SafeArrayPutElement(psa,&index,&bval[index])))
AfxMessageBox(_T("错误。"));

}
varChunk.vt =VT_ARRAY|VT_UI1;
varChunk.parray=psa;
try
{
m_pRecord->Fields->GetItem("ImageData")->AppendChunk(varChunk);
}
catch (_com_error e)
{
AfxMessageBox(_T("错误。"));
}
::VariantClear(&varChunk);
::SafeArrayDestroyData(psa);
if (uIsRead<ChunkSize)break;

}
f.Close();
}

INT CDlgTest::GetEncoderClsid(const WCHAR* format, CLSID* pClsid)
{
UINT num = 0; // number of image encoders
UINT size = 0; // size of the image encoder array in bytes

ImageCodecInfo* pImageCodecInfo = NULL;

GetImageEncodersSize(&num, &size);
if(size == 0)
return -1; // Failure

pImageCodecInfo = (ImageCodecInfo*)(malloc(size));
if(pImageCodecInfo == NULL)
return -1; // Failure

GetImageEncoders(num, size, pImageCodecInfo);

for(UINT j = 0; j < num; ++j)
{
if( wcscmp(pImageCodecInfo[j].MimeType, format) == 0 )
{
*pClsid = pImageCodecInfo[j].Clsid;
free(pImageCodecInfo);
return j; // Success
} 
}

free(pImageCodecInfo);
return -1; // Failure
}