关于GDI+使用双缓存显示图片

daodao315 2010-05-03 07:15:47

在一个基于单文档的程序中使用GDI+显示图片，比如jpg图片，为了使窗口大小改变时图片不产生闪烁现象，要使用双缓存处理。我是这样写的，在view类里面定义了两个成员变量Graphics *memgraph 和 Bitmap *membmp；在文件打开响应函数里面相关代码如下：



CFileDialog openfile(TRUE,NULL,NULL,OFN_HIDEREADONLY | OFN_OVERWRITEPROMPT,L"bmp,jpg|*.bmp;*.jpg|                All Support File|*.bmp;*.jpg;*.png|");



if(openfile.DoModal()==IDOK)

{

  strpath=openfile.GetPathName();

  Bitmap *image=Bitmap::FromFile(strpath);     

  Bitmap bmp(image->GetWidth(),image->GetHeight());	

  membmp=new Bitmap(image->GetWidth(),image->GetHeight());

  memgraph=Graphics::FromImage(membmp);

  TextureBrush brush(image);

  memgraph->FillRectangle(&brush,0,0,image->GetWidth(),image->GetHeight());

}

在OnDraw()里面的相关代码为：



if(!strpath.IsEmpty()) 

{  

  CDC *pDC=GetDC();	

  Graphics graph(pDC->GetSafeHdc());

  CRect winrect;		

  GetClientRect(winrect);		

  graph.DrawImage(membmp,0,0,winrect.Width(),winrect.Height());

  ReleaseDC(pDC);

}

这样还是有闪烁，我刚接触GDI+处理图像，请大家帮忙告诉一下GDI+中的防止闪烁现象应该怎么做呢.... 先谢谢了^_^

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尹成 2010-05-04

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另解：

void CXXXXXDlg::OnPaint()  

{

  CPaintDC dc(this); // device context for painting



  // TODO: Add your message handler code here

  CDC memDC; // 缓存DC

  CDC selDC; // 选入图片的DC

  HBITMAP hBmp;

  HBITMAP hOldBMP;

  memDC.CreateCompatibleDC(&dc);

  selDC.CreateCompatibleDC(&dc);

  hBmpMem = CreateCompatibleBitmap(dc.m_hDC, m_nCx, m_nCy);



  // 画背景到缓存DC

  memDC.FillSolidRect(0, 0, m_nCx, m_nCy, RGB(0, 0, 0));   

    

  // 画图片到缓存DC

  hBmpMem = LoadBitmap(NULL, MAKEINTRESOURCE(ID_BMP1));

  hOldBMP = memDC.SelectObject(hBmpMem);

  memDC.BitBlt(0, 0, m_nCx, m_nCy, &selDC, 0, 0, SRCCOPY);



  // 从缓存画到窗口DC

  dc.BitBlt(0, 0, m_nCx, m_nCy, &memDC, 0, 0, SRCCOPY);

    

  // 清除GDI对象



}

如果有闪烁, 处理一下 WM_ERASEBKGND 消息, 直接返回TRUE

ON_WM_ERASEBKGND()



BOOL CXXXXXDlg::OnEraseBkgnd(CDC* pDC)  

{

  return TRUE;

}

尹成 2010-05-04

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void   CRightView::OnDraw(CDC   *pDC)   

  {   

  GetClientRect(&m_rectClient);   

    

  CDC   dc;   

  dc.CreateCompatibleDC(pDC);   

  CBitmap   bitmap;   

  bitmap.CreateCompatibleBitmap(pDC,m_rectClient.Width(),m_rectClient.Height());   

  CBitmap*   pOldBitmap;   

  pOldBitmap   =   dc.SelectObject(&bitmap);   

    

  //CBrush br(RGB(255,255,255));   

  //dc.FillRect(m_rectClient,   &br);   

    

  CBrush br(OUTRGB);   

  CBrush* pOldBrush   =   dc.SelectObject(&br);   

  dc.Rectangle(0,0,m_rectClient.Width(),m_rectClient.Height());   

    

  dc.SetBkMode(TRANSPARENT);   

  //   

  //   sort   of   plane   model   

  //   

  for(int   i   =   0;   i   <   GetDocument()->m_arrayPlane.GetSize();   i++)   

  {   

  int   yPos   =   i*PLANESPACE+10   -   GetDocument()->m_nRScrollPos;   

    

  if(GetDocument()->IsBoundary(i))   

  {   

  dc.MoveTo(m_rectClient.left,yPos+22);   

  dc.LineTo(m_rectClient.right,yPos+22);   

  }   

    

  CString   strNO   =   GetDocument()->m_arrayPlane[i].m_strPlaneNO;   

  dc.TextOut(5,yPos,strNO.Right(2));   

  }   

    

  pDC->BitBlt(m_rectClient.left,   

  m_rectClient.top,     

  m_rectClient.Width(),   

  m_rectClient.Height(),   

  &dc,   

  0,   

  0,   

  SRCCOPY);   

    

  dc.SelectObject(pOldBitmap);   

  }

daodao315 2010-05-04

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[Quote=引用 3 楼 yincheng01 的回复:]

另解：C/C++ code
void CXXXXXDlg::OnPaint()
{
CPaintDC dc(this); // device context for painting

// TODO: Add your message handler code here
CDC memDC; // 缓存DC
CDC selDC; // 选入图片的DC
HBITMAP ……
[/Quote]

谢谢啊，现在明白双缓存的意思了....^_^

daodao315 2010-05-03