用C++实现半透明按钮控件(PNG,GDI+)

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 }

透明的关键：注意后面调用此方法的代码关键在于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 }

附：从资源加载PNG图片View Code

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 memory12       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 stream17       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 stream23       pImg=Gdiplus::Image::FromStream(pstm);24      // free/release stuff25       GlobalUnlock(m_hMem);26      pstm->Release();27      FreeResource(lpRsrc);28      return TRUE;29 }

平铺图片的代码

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::OnPaintrn");

附:PNGButton类代码下载
原文链接: https://www.cnblogs.com/Lexy/archive/2011/04/09/2010418.html

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