学步园

使用MFC实现上面的按钮半透明效果能看到父窗口中的内容，上面是效果图(一个是带背景图片的、另一个是不带的)。

控件继承自CWnd类(彩色的部分是窗口的背景图片、按钮是PNG图片，第二个图标是鼠标指向时的效果)。

图标的绘制使用GDI+绘制PNG图片，在此不多说了(处理WM_PAINT消息):

void PNGButton::OnPaint()
{  
 CPaintDC dc(this);    
 Graphics g(dc.m_hDC);   
 if(DrawBorder){   
　　　　g.DrawImage(hoverBg,0,0);//画鼠标指向时的亮色背景  
 } 
 g.DrawImage(this->bg,0,0);//画按钮图标
  g.ReleaseHDC(dc.m_hDC);
}

 

当按钮多次重画时，颜色会一次比一次深。我们要清除先前绘制的图像，这时就需要通知父窗口重绘制定的区域了：

void PNGButton::PaintParent()
{  
 CRect   rect; 
 GetWindowRect(&rect); 
 GetParent()-> ScreenToClient(&rect); 
 GetParent()-> InvalidateRect(&rect);
}

捕获鼠标指向或移出事件(处理WM_MOUSEMOVE,WM_MOUSEOVER,WM_MOUSELEAVE消息)：

 

void PNGButton::OnMouseHover(UINT nFlags, CPoint point)
{    
 DrawBorder=true;
 PaintParent();//通知父窗口重绘特定区域，会引发控件自身的重绘
}


 void PNGButton::OnMouseLeave()
{    
 m_is_mouse_over =   false; 
 m_is_tracked =   false;  
 DrawBorder=false;
 PaintParent();  //通知父窗口重绘特定区域，会引发控件自身的重绘
 CWnd::OnMouseLeave();
}


 void PNGButton::OnMouseMove(UINT nFlags, CPoint point)
{
 m_is_mouse_over   =   true;  
 if(!m_is_tracked) 
 { 
  TRACKMOUSEEVENT   tme; 
  tme.cbSize  =   sizeof(TRACKMOUSEEVENT); 
  tme.dwFlags  =   TME_LEAVE|TME_HOVER;  
  tme.hwndTrack   =   GetSafeHwnd(); 
  tme.dwHoverTime =   80; 
  _TrackMouseEvent(&tme);  
  m_is_tracked   =   true;    
 }   
 CWnd::OnMouseMove(nFlags, point);
}

附：

从资源加载PNG图片

#pragma once<br /> #include "stdafx.h"<br /> using namespace Gdiplus; </p> <p>static bool ImageFromIDResource(UINT nID, LPCTSTR sTR,Image * &pImg)<br /> {<br /> HINSTANCE hInst = AfxGetResourceHandle();<br /> HRSRC hRsrc = ::FindResource (hInst,MAKEINTRESOURCE(nID),sTR); // type<br /> if (!hRsrc)<br /> return FALSE;</p> <p> // load resource into memory<br /> DWORD len = SizeofResource(hInst, hRsrc);<br /> BYTE* lpRsrc = (BYTE*)LoadResource(hInst, hRsrc);<br /> if (!lpRsrc)<br /> return FALSE;</p> <p> // Allocate global memory on which to create stream<br /> HGLOBAL m_hMem = GlobalAlloc(GMEM_FIXED, len);<br /> BYTE* pmem = (BYTE*)GlobalLock(m_hMem);<br /> memcpy(pmem,lpRsrc,len);<br /> IStream* pstm;<br /> CreateStreamOnHGlobal(m_hMem,FALSE,&pstm);</p> <p> // load from stream<br /> pImg=Gdiplus::Image::FromStream(pstm);<br /> // free/release stuff<br /> GlobalUnlock(m_hMem);<br /> pstm->Release();<br /> FreeResource(lpRsrc);<br /> return TRUE;<br /> }

 平铺图片的代码

      CPaintDC dc(this); 
      CRect rect; 
      GetClientRect(rect);
      CBrush bs(RGB(240,240,240));//窗口背景色
       dc.FillRect(&rect,&bs);        //窗口着色
      //填充背景图片：平铺
       Graphics g(dc.m_hDC);    
      if(has_bg) g.DrawImage(this->bg,0,0); 
      Gdiplus::TextureBrush bbs(this->img);
     g.FillRectangle(&bbs,0,0,rect.Width(),this->img->GetHeight()); 
     g.ReleaseHDC(dc.m_hDC);
     //TRACE(L"CMainFrame::OnPaint/r/n");