CStatic中保持图形比例不变，尽量填充控件空间的代码

void CImagePreviewStatic::DrawItem(LPDRAWITEMSTRUCT    /*lpDrawItemStruct*/)

{

    Unit  units;

    CRect rect;if (m_img2 !=NULL) {//获取到HDC
        HWND hWnd = GetParent()->m_hWnd;

        HDC hDc=::GetDC(hWnd);//获取画的位置
        GetWindowRect(&rect);

        ::ScreenToClient(hWnd, (LPPOINT)&rect);

        ::ScreenToClient(hWnd, (LPPOINT)(&rect) + 1);

        ::SetStretchBltMode(hDc, COLORONCOLOR);int rectWidth = rect.right -rect.left;int rectHeight= rect.bottom -rect.top;//在这儿计算显示区域
        int nHeight = m_img2->GetHeight();int nWidth  = m_img2->GetWidth();//假设图像高度不变，则在当前RECT下，需要多少的宽度
        int nAdjWidth = (rectHeight*nWidth)/nHeight;//如果当前宽度大于现有宽度，则宽度不变，调整高度信息
        if (nAdjWidth >rectWidth) {int nAdjHeight = (rectWidth*nHeight)/nWidth;

            rect.bottom= rect.top +nAdjHeight;

        }else{//只需要调整不等于的情况
            if (nAdjWidth !=rectWidth){

                rect.right= rect.left +nAdjWidth;

            }

        }//画图片
        m_img2->Draw(hDc,rect);

    }

}