利用UpdateLayeredWindow函数制作透明窗口时BMP的Alpha通道的问题

void CDigitalClock::Update()<br />
{<br />
	// Create the alpha blending bitmap<br />
	BITMAPINFO bmi;        // bitmap header<br />
	ZeroMemory(&bmi, sizeof(BITMAPINFO));<br />
	bmi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);<br />
	bmi.bmiHeader.biWidth = m_Width;<br />
	bmi.bmiHeader.biHeight = m_Height;<br />
	bmi.bmiHeader.biPlanes = 1;<br />
	bmi.bmiHeader.biBitCount = 32;   // four 8-bit components<br />
	bmi.bmiHeader.biCompression = BI_RGB;<br />
	bmi.bmiHeader.biSizeImage = m_Width * m_Height * 4;</p>
<p>	BYTE *pvBits;          // pointer to DIB section<br />
	HBITMAP hbitmap = CreateDIBSection(NULL, &bmi, DIB_RGB_COLORS,<br />
		(void **)&pvBits, NULL, 0);<br />
	ZeroMemory(pvBits, bmi.bmiHeader.biSizeImage);<br />
	HDC hMemDC = CreateCompatibleDC(GetDC(m_hWnd));<br />
	HBITMAP hOriBmp = (HBITMAP)SelectObject(hMemDC, hbitmap);</p>
<p>	HFONT *oldFont=NULL;<br />
	static char str_time[10]={“”};<br />
	CTime t=CTime::GetCurrentTime();<br />
	sprintf(str_time,”%02d:%02d.%02d”,<br />
	    t.GetHour(),t.GetMinute(),t.GetSecond());<br />
	CRect rt;<br />
	GetClientRect(m_hWnd, &rt);</p>
<p>	oldFont = (HFONT*)SelectObject(hMemDC,g_this->GetFont());<br />
	SetBkColor(hMemDC,RGB(0,0,0));<br />
	SetBkMode(hMemDC,TRANSPARENT);<br />
	GetClientRect(m_hWnd, &rt);<br />
	FillRect(hMemDC,&rt,CBrush(RGB(128,128,128)));<br />
	SetTextColor(hMemDC,RGB(255,255,255));<br />
	DrawText(hMemDC, str_time,strlen(str_time), &rt,<br />
		DT_CENTER|DT_VCENTER|DT_SINGLELINE);</p>
<p>	GetWindowRect(m_hWnd,rt);<br />
	POINT ptDst = {rt.left,rt.top};<br />
	POINT ptSrc = {0, 0};<br />
	SIZE WndSize = {m_Width, m_Height};<br />
	//ULW_COLORKEY  1  ULW_ALPHA     2 ULW_OPAQUE    4<br />
	//AC_SRC_OVER   0  AC_SRC_ALPHA  1<br />
	BLENDFUNCTION blendPixelFunction={AC_SRC_OVER, 0,<br />
	    m_iSourceConstantAlpha,AC_SRC_ALPHA };</p>
<p>	//在这里设置BMP的Alpha值<br />
	//内存中的数据格式为 RR GG BB AL<br />
	for(int m=3;m<m_Width * m_Height * 4;m+=4)<br />
		*(pvBits+m)=(BYTE)m_iImageAlpha;</p>
<p>	HDC hdcScreen=::GetDC (m_hWnd);<br />
	BOOL bRet =_UpdateLayeredWindow(m_hWnd, hdcScreen, &ptDst, &WndSize,<br />
		hMemDC,<br />
		&ptSrc, RGB(0,0,0), &blendPixelFunction, 2);<br />
	//_ASSERT(bRet); // something was wrong….<br />
	// Delete used resources<br />
	SelectObject(hMemDC,oldFont);<br />
	SelectObject(hMemDC, hOriBmp);<br />
	DeleteObject(hbitmap);<br />
	DeleteDC(hMemDC);<br />
}<br />

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本文链接：https://www.cnblogs.com/nlsoft/archive/2013/03/10/2952681.html

利用UpdateLayeredWindow函数制作透明窗口时BMP的Alpha通道的问题

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