对话框显示图像的简单方法

1、获取图像的内存数据
2、调用BufferToHBITMAP()函数，将图像数据转为HBITMAP
3、在OnDraw里面，利用双缓冲，贴图像数据

详细说明：
1、利用FILE来打开图像文件，利用下面函数获取文件大小。再用fread，将图像文件读取到内存中。

long Getlength( FILE *fp ){    long cur_pos;    long len;    //取得当前文件流的读取位置    cur_pos = ftell( fp );    //将文件流的读取位置设为文件末尾    fseek( fp, 0, SEEK_END );    //获取文件末尾的读取位置,即文件大小    len = ftell( fp );    //将文件流的读取位置还原为原先的值    fseek( fp, cur_pos, SEEK_SET );    return len;}

2、HBITMAP BufferToHBITMAP(char* pBMPBuffer,int& nbmW,int& nbmH,CWnd* pWnd)
{
HBITMAP hShowBMP;
LPSTR hDIB,lpBuffer = pBMPBuffer;
LPVOID lpDIBBits;
BITMAPFILEHEADER bmfHeader;
DWORD bmfHeaderLen;
bmfHeaderLen = sizeof(bmfHeader);
strncpy((LPSTR)&bmfHeader,(LPSTR)lpBuffer,bmfHeaderLen);
if (bmfHeader.bfType != (*(WORD*)"BM")) return NULL;
hDIB = lpBuffer + bmfHeaderLen;
BITMAPINFOHEADER &bmiHeader = *(LPBITMAPINFOHEADER)hDIB ;
BITMAPINFO &bmInfo = *(LPBITMAPINFO)hDIB ;
nbmW = bmiHeader.biWidth;
nbmH = bmiHeader.biHeight;
lpDIBBits=(lpBuffer)+((BITMAPFILEHEADER *)lpBuffer)->bfOffBits;
CClientDC dc(pWnd);
hShowBMP = CreateDIBitmap(dc.m_hDC,&bmiHeader,CBM_INIT,lpDIBBits,
&bmInfo,DIB_RGB_COLORS);
return hShowBMP;
}

3、OnDraw函数里面的实现：

if (NULL == m_pBMPBuffer)    {        return;    }    if (NULL == m_hBitmap)    {        m_hBitmap = BufferToHBITMAP(m_pBMPBuffer,m_nbmW,m_nbmH,this);    }    HBITMAP OldBitmap;    CDC MemDC;    MemDC.CreateCompatibleDC(pDC);    OldBitmap=(HBITMAP)MemDC.SelectObject(m_hBitmap);     CBitmap* pBitmap = CBitmap::FromHandle(m_hBitmap);    if(m_nbmW == 0 || m_nbmH == 0)    {        return;    }    CRect rect;    GetClientRect(&rect);    ::SetStretchBltMode (pDC->m_hDC, HALFTONE);     pDC->StretchBlt(0,0,rect.Width(),rect.Height(),&MemDC,0,0,m_nbmW,m_nbmH,SRCCOPY);    MemDC.SelectObject(OldBitmap);