一个类似VS2010中的CMemDC类，VC6中用

/使用方法/参考  http://blog.csdn.net/mplus/article/details/6131526 ，创建CMemDC对象

//时传一个已有的DC的指针进去（大小可选）如：

/*void CDemoView::OnDraw(CDC* pDC)

 { 
	 CFont  font; 
	 font.CreateFontIndirect(&m_lf); 
	 CMemDC  pMemDC(pDC); 
	 CFont* oldfont = pMemDC->SelectObject(&font); 
        //..Draw something here. 
	 pMemDC->SelectObject(oldfont); 
 } 

*/

//以及百度知道问题

//MemDC.H

#ifndef _MEMDC_H_

#define _MEMDC_H_

//////////////////////////////////////////////////

// CMemDC - memory DC

//

// Author: Keith Rule

// Email:  [e-mail]

// Copyright 1996-1997, Keith Rule

//

// You may freely use or modify this code provided this

// Copyright is included in all derived versions.

//

// This class implements a memory Device Context

class CMemDC : public CDC 

{

private:

CBitmap* m_bitmap;

CBitmap* m_oldBitmap;

CDC* m_pDC;

CRect m_rcBounds;

bool  m_bMemDC;

public:

void Construct(CDC* pDC)

{

        ASSERT(pDC != NULL); 

        // Some initialization

        m_pDC = pDC;

        m_oldBitmap = NULL;

        m_bMemDC = !pDC->IsPrinting();

        if (m_bMemDC) {

            // Create a Memory DC

            CreateCompatibleDC(pDC);

            pDC->LPtoDP(&m_rcBounds);

m_bitmap = new CBitmap;

            m_bitmap->CreateCompatibleBitmap(pDC, m_rcBounds.Width(), m_rcBounds.Height());

            m_oldBitmap = SelectObject(m_bitmap);

            SetMapMode(pDC->GetMapMode());

            pDC->DPtoLP(&m_rcBounds);

            SetWindowOrg(m_rcBounds.left, m_rcBounds.top);

        } else {

            // Make a copy of the relevent parts of the current DC for printing

            m_bPrinting = pDC->m_bPrinting;

            m_hDC       = pDC->m_hDC;

            m_hAttribDC = pDC->m_hAttribDC;

        }

        // Fill background 

        FillSolidRect(m_rcBounds, pDC->GetBkColor());

    }

CMemDC(CDC* pDC                       ) : CDC() { pDC->GetClipBox(&m_rcBounds); Construct(pDC); }

CMemDC(CDC* pDC, const CRect& rcBounds) : CDC()

{

CreateCompatibleDC(pDC);

m_bitmap = new CBitmap;

m_bitmap->CreateCompatibleBitmap(pDC, rcBounds.Width(), rcBounds.Height());

m_oldBitmap = SelectObject(m_bitmap);

m_pDC = pDC;

m_rcBounds = rcBounds;

}

~CMemDC() 

{

m_pDC->BitBlt(m_rcBounds.left, m_rcBounds.top, m_rcBounds.Width(), m_rcBounds.Height(), 

this, m_rcBounds.left, m_rcBounds.top, SRCCOPY);

SelectObject(m_oldBitmap);

if (m_bitmap != NULL) 

delete m_bitmap;

}

CMemDC* operator->() 

{

return this;

}

};

#endif