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):

 1 void PNGButton::OnPaint()

 2 {

 3  CPaintDC dc(this);

 4  Graphics g(dc.m_hDC);

 5  if(DrawBorder){

 6 　　　　g.DrawImage(hoverBg,0,0);//画鼠标指向时的亮色背景

 7  }

 8  g.DrawImage(this->bg,0,0);//画按钮图标

 9   g.ReleaseHDC(dc.m_hDC);

10 }

关键在于InvalidateRect函数:通知父窗口重新绘制特定区域,执行此函数后按钮所在区域就被父窗口绘制的内容覆盖.在父窗口绘制完成后,
按钮也会收到WM_PAINT消息,执行上面的一段OnPaint代码.

1 void PNGButton::PaintParent()

2 {

3  CRect   rect;

4  GetWindowRect(&rect);

5  GetParent()-> ScreenToClient(&rect);

6  GetParent()-> InvalidateRect(&rect);

7 }

 

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

 

 1 void PNGButton::OnMouseHover(UINT nFlags, CPoint point)

 2 {

 3  DrawBorder=true;

 4  PaintParent();//通知父窗口重绘特定区域，会引发控件自身的重绘

 5 }

 6

 7

 8  void PNGButton::OnMouseLeave()

 9 {

10  m_is_mouse_over =   false;

11  m_is_tracked =   false;

12  DrawBorder=false;

13  PaintParent();  //通知父窗口重绘特定区域，会引发控件自身的重绘

14  CWnd::OnMouseLeave();

15 }

16

17

18  void PNGButton::OnMouseMove(UINT nFlags, CPoint point)

19 {

20  m_is_mouse_over   =   true;

21  if(!m_is_tracked)

22  {

23   TRACKMOUSEEVENT   tme;

24   tme.cbSize  =   sizeof(TRACKMOUSEEVENT);

25   tme.dwFlags  =   TME_LEAVE|TME_HOVER;

26   tme.hwndTrack   =   GetSafeHwnd();

27   tme.dwHoverTime =   80;

28   _TrackMouseEvent(&tme);

29   m_is_tracked   =   true;

30  }

31  CWnd::OnMouseMove(nFlags, point);

32 }

 

 1 #pragma once

 2 #include "stdafx.h"

 3  using namespace Gdiplus;

 4

 5  static bool ImageFromIDResource(UINT nID, LPCTSTR sTR,Image * &pImg)

 6 {

 7      HINSTANCE hInst = AfxGetResourceHandle();

 8      HRSRC hRsrc = ::FindResource (hInst,MAKEINTRESOURCE(nID),sTR); // type

 9       if (!hRsrc)

10       return FALSE;

11      // load resource into memory

12       DWORD len = SizeofResource(hInst, hRsrc);

13      BYTE* lpRsrc = (BYTE*)LoadResource(hInst, hRsrc);

14      if (!lpRsrc)

15       return FALSE;

16      // Allocate global memory on which to create stream

17       HGLOBAL m_hMem = GlobalAlloc(GMEM_FIXED, len);

18      BYTE* pmem = (BYTE*)GlobalLock(m_hMem);

19      memcpy(pmem,lpRsrc,len);

20      IStream* pstm;

21      CreateStreamOnHGlobal(m_hMem,FALSE,&pstm);

22      // load from stream

23       pImg=Gdiplus::Image::FromStream(pstm);

24      // free/release stuff

25       GlobalUnlock(m_hMem);

26      pstm->Release();

27      FreeResource(lpRsrc);

28      return TRUE;

29 }

 1     CPaintDC dc(this);

 2     CRect rect;

 3     GetClientRect(rect);

 4     CBrush bs(RGB(240,240,240));//窗口背景色

 5      dc.FillRect(&rect,&bs);        //窗口着色

 6     //填充背景图片：平铺

 7      Graphics g(dc.m_hDC);

 8     if(has_bg) g.DrawImage(this->bg,0,0);

 9     Gdiplus::TextureBrush bbs(this->img);

10     g.FillRectangle(&bbs,0,0,rect.Width(),this->img->GetHeight());

11     g.ReleaseHDC(dc.m_hDC);

12     //TRACE(L"CMainFrame::OnPaint\r\n");