在图片上进行画图操作

m_pDesImg = Image::FromFile(m_csPicFileName);

Graphics g(m_pDesImg);

if ( m_signArray.GetSize() ==0)
{
IStream *pStream = NULL;
RectF rtF(0, 0, 0, 0);
m_pTmpSealImg = Image::FromStream(pStream);
g.DrawImage(m_pTmpSealImg, rtF);

} 

使用gdi+的graphics（Image *）构造一个对象

IStream *pStream = NULL;
HRESULT hr = CreateStreamOnHGlobal(NULL, TRUE, &pStream);

m_pTmpSealImg = Image::FromStream(pStream);



g.DrawImage(m_pTmpSealImg, rtF);

然后把你所要画的从字节流中取出即可。