如何截取位图的一部分

wangshuiqing 2010-09-10 11:48:43

有一幅位图，想从中截取出某个矩形，存为另一幅位图。下面是我的代码，针对8位位图的，不知道哪里有问题，总是出现内存溢出



if (m_hBitmap==NULL)

    return;

	CRect rect;

	rect.left=50;

	rect.top=50;

	rect.right=150;

	rect.bottom=100;

	int iWidth=rect.Width();

	int iHeight=rect.Height();

	int iBitCounts=8;

	DWORD dwSize=iWidth*iHeight*iBitCounts/8;

	BYTE* pNewImageBuffer=new BYTE[dwSize];

	

	BITMAP bm; 

	::GetObject(m_hBitmap,sizeof(bm),(LPVOID)&bm);

	m_bmWidth=bm.bmWidth;

	m_bmHeight=bm.bmHeight;

	

	BYTE* pOldImageBuffer=(BYTE*)(bm.bmBits);

	int iWidthBytes=bm.bmWidthBytes;

	BYTE* pNew=(BYTE*)pNewImageBuffer;

	BYTE* pOld=(BYTE*)pOldImageBuffer;

	pOld+=(bm.bmHeight-rect.bottom-1)*bm.bmWidthBytes;

	for (int i=rect.bottom;i>=rect.top;i--)

	{

		for (int j=rect.left;j<=rect.right;j++)

		{

			*pNew=*(pOld+j);

			pNew++;

		}

		if (i>rect.top)

			pOld+=bm.bmWidthBytes;

	}



	CBitmap newBmp;

	newBmp.CreateBitmap(iWidth,iHeight,1,iBitCounts,(void*)pNewImageBuffer);//到这里不管换成什么代码，只要涉及到new，即动态分配内存的，都会出现out of memory的那个对话框



	CDC* pDC=m_picCtrl.GetDC();

	CDC MemDC;

	MemDC.CreateCompatibleDC(pDC);

	CRect clientRect;

	m_picCtrl.GetClientRect(clientRect);

	CBitmap* pOldBitmap=MemDC.SelectObject(&newBmp);

	pDC->BitBlt(100,100,clientRect.Width(),clientRect.Height(),&MemDC,0,0,SRCCOPY);//绘制位图

	MemDC.SelectObject(pOldBitmap);

	DeleteObject(newBmp);

	ReleaseDC(&MemDC);

	delete pNewImageBuffer;