利用BMP通道和UpdateLayeredWindow制作边缘透明不规则窗口

1.新建 颜色模式RGB颜色 背景内容为透明


2.填充黑色  因为Alpha通道黑色+前景色黑色时会完全透明


3.用滤镜做如下效果


4.选择全部区域并复制 增加Alpha通道


5.通道中只选Alpha通道 并粘贴选择区域


6.存盘为BMP格式 这是Alpha通道自动选择


7.BMP选项为Windows 32位


8.效果图 边沿透明不规则


说明：UpdateLayeredWindow函数做透明处理时有两个参数可以调整透明度
一个是BMP中的Alpha通道的参数，还有一个是BLENDFUNCTION结构中的SourceConstantAlpha参数

void CUpdateLayeredWindow_testDlg::Test()

{

	char bmpFileName[] = {"./back.bmp"};

	HWND hWnd = this->GetSafeHwnd();

	typedef BOOL (WINAPI *pfnUpdateLayeredWindow)(HWND hWnd, HDC hdcDst, POINT *pptDst,

		SIZE *psize, HDC hdcSrc, POINT *pptSrc, COLORREF crKey,

		BLENDFUNCTION *pblend, DWORD dwFlags);

	pfnUpdateLayeredWindow s_UpdateLayeredWindow;

	HMODULE hSysDll = LoadLibrary(_T("USER32.DLL"));

	if(!hSysDll) return;

	s_UpdateLayeredWindow = 

		(pfnUpdateLayeredWindow)GetProcAddress(hSysDll, 

		"UpdateLayeredWindow");

	if(!s_UpdateLayeredWindow) return;

	HBITMAP hbitmap = (HBITMAP)::LoadImage(AfxGetInstanceHandle(),bmpFileName,

		IMAGE_BITMAP,0,0,LR_LOADFROMFILE);

	if(!hbitmap) return;

	DWORD dwExStyle = ::GetWindowLong(hWnd, GWL_EXSTYLE);

	if ((dwExStyle & 0x80000) != 0x80000)

		::SetWindowLong(hWnd, GWL_EXSTYLE, dwExStyle ^ 0x80000);

	HDC hMemDC = CreateCompatibleDC(NULL);

	HBITMAP hOriBmp = (HBITMAP)SelectObject(hMemDC, hbitmap);

	BITMAP bi;

	CBitmap bm;

	bm.Attach(hbitmap);

	bm.GetBitmap(&bi);

	bm.Detach();

	SetWindowPos(NULL,0,0,bi.bmWidth,bi.bmHeight,0);

	RECT WndRect;

	::GetWindowRect(hWnd, &WndRect);

	POINT ptDst = {WndRect.left, WndRect.top};

	POINT ptSrc = {0, 0};

	SIZE WndSize = {WndRect.right-WndRect.left,WndRect.bottom-WndRect.top};

	#define AC_SRC_ALPHA 0x01

	#define ULW_ALPHA 0x00000002

	BLENDFUNCTION blendPixelFunction= { AC_SRC_OVER, 0, 255, AC_SRC_ALPHA };

	BOOL bRet= s_UpdateLayeredWindow(m_hWnd, NULL, &ptDst, &WndSize, hMemDC,

		&ptSrc, 0, &blendPixelFunction, 2);

	SelectObject(hMemDC, hOriBmp);

	DeleteObject(hbitmap);

	DeleteDC(hMemDC);

}

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