巧用StretchBlt实现图像放大镜

1、巧用StretchBlt实现图像放大镜 - 在有些应用中需要对图像的局部进行放大，本例程用VC+ 5.0编写，用CDC的StretchBlt实现图像放大镜，主要有以下功能：1.移动MOUSE放大显示图像的不同部位，2.左击增加放大倍率，3.右击减少放大倍率。 当放大倍率较大时产生抖动。 - 实现过程： - 1.使用AppWizard生成SDI应用IMAGE。 - 2.为CImageView增加以下成员数据： CSize m_sizeDest; CSize m_sizeSource; CBitmap * m_pBitmap; CDC * m_pdcMem; int oldx,oldy,s,d;

2、file:/s确定被放大区域， d确定放大显示区域，放大倍率=d/s bool recover; long mana;- 3在资源中加入自己喜欢的位图并设为IDB_BITMAP1。 - 4对CImageView的以下消息编程： CImageView:CImageView()/ Initialize values m_pdcMem = new CDC;m_pBitmap = new CBitmap;recover = true;s = 30; d = 45; mana = SRCCOPY;CImageView:CImageView()delete m_pdcMem;delete m_pBitma

3、p;void CImageView:OnDraw(CDC* pDC)static bool load;if (!load) BITMAP bm; load = !load; m_pBitmap- >LoadBitmap(IDB_BITMAP1); m_pdcMem- >CreateCompatibleDC(pDC); m_pdcMem- >SelectObject(m_pBitmap); m_pBitmap- >GetObject(sizeof(bm),&bm); m_sizeSource.cx = bm.bmWidth; m_sizeSource.cy = b

4、m.bmHeight; m_sizeDest = m_sizeSource;pDC- >StretchBlt(0,0,m_sizeSource.cx,m_sizeSource.cy,m_pdcMem,0,0,m_sizeSource.cx,m_sizeSource.cy,mana);else pDC- >StretchBlt(0,0,m_sizeSource.cx,m_sizeSource.cy,m_pdcMem,0,0,m_sizeSource.cx,m_sizeSource.cy,mana);void CImageView:OnMouseMove(UINT nFlags, CP

5、oint point) CString cord; int dd; CRect srect,drect,mrect; CMainFrame * pFrame = (CMainFrame *)AfxGetApp()- >m_pMainWnd ; CStatusBar * pStatus = &pFrame- >m_wndStatusBar ; if (pStatus) cord.Format("X = %d, Y = %d",point.x,point.y); pStatus- >SetPaneText (1,cord); srect.left =

6、point.x - s; srect.top = point.y - s; srect.right = point.x + s; srect.bottom = point.y + s; drect.left = point.x - d; drect.top = point.y - d; drect.right = point.x + d; drect.bottom = point.y + d; mrect.left = oldx - d; mrect.top = oldy - d; mrect.right = oldx + d; mrect.bottom = oldy + d; dd = 2*

7、d; CDC * pDC = GetDC(); OnPrepareDC(pDC); if (recover) pDC- >BitBlt(mrect.left,mrect.top,dd,dd,m_pdcMem,mrect.left,mrect.top,mana); pDC- >StretchBlt(drect.left,drect.top,drect.Width(),drect.Height(),m_pdcMem,srect.left,srect.top,srect.Width(),srect.Height(),SRCCOPY); oldx = point.x; oldy = poi

8、nt.y; ReleaseDC(pDC);recover = true;CView:OnMouseMove(nFlags, point);void CImageView:OnRButtonDown(UINT nFlags, CPoint point) if (d > 5) CDC * pDC = GetDC(); pDC- >StretchBlt(oldx - d,oldy - d,2*d,2*d,m_pdcMem,oldx - d,oldy - d,2*d,2*d,mana); d -= 10; ReleaseDC(pDC); CImageView:OnMouseMove(nFlags, point); CView:OnRButtonDown(nFlags, point);void CImageView:OnLButtonD