通过鼠标画一次性矩形 + 绘制半透膜矩形

最新推荐文章于 2023-08-21 21:31:44 发布

原创最新推荐文章于 2023-08-21 21:31:44 发布 · 796 阅读

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绘制一次性矩形的原理就是不断的画新矩形，并不断的擦出旧矩形

void CMeiTuDlg::OnLButtonDown(UINT nFlags, CPoint point)
{
	// TODO: 在此添加消息处理程序代码和/或调用默认值
	down = point;
	old = point;
	DRAW = TRUE;
	CDialogEx::OnLButtonDown(nFlags, point);
}

void CMeiTuDlg::OnMouseMove(UINT nFlags, CPoint point)
{
	// TODO: 在此添加消息处理程序代码和/或调用默认值
	CClientDC dc(this);
	dc.SetROP2(R2_NOT);   //此为关键!!! 
	dc.SelectStockObject(NULL_BRUSH); //不使用画刷
	if (TRUE == DRAW)   //根据是否有单击判断是否可以画矩形 
	{    
		dc.Rectangle(CRect(down,old)); 
		dc.Rectangle(CRect(down,point)); 
		old = point; 
		//下面用于将信息显示在窗口标题
		/*char buf[128];
		memset(buf, 0, 128);
		sprintf(buf, ("起始:(%d,%d),终点:(%d,%d),大小：%d * %d"),
			down.x,down.y,point.x, point.y, abs(point.x- down.x), abs(point.y- down.y));
		SetWindowText(buf);*/
	}
	CDialogEx::OnMouseMove(nFlags, point);
}

void CMeiTuDlg::OnLButtonUp(UINT nFlags, CPoint point)
{
	// TODO: 在此添加消息处理程序代码和/或调用默认值
	up = point;
	DRAW = FALSE; //重置绘制矩形框标志  
	//消隐最后的一个矩形（其原理跟拖动时矩形框绘制原理相同）
	CClientDC dc(this);  
	dc.SetROP2(R2_NOT);
	dc.SelectStockObject(NULL_BRUSH); 
	dc.Rectangle(CRect(down,old)); 
	CDialogEx::OnLButtonUp(nFlags, point);
}

绘制半透明矩形，借鉴的哪儿的忘了==

void MyButton::DrawAlphaRect(CRect rect)
{
	CDC *dc = GetDC();
	CDC cdc;
	cdc.CreateCompatibleDC(dc);
	CBitmap bitmap, *pOldBitmap;
	bitmap.CreateCompatibleBitmap(dc, rect.right, rect.bottom);
	CRect src(rect);
	src.OffsetRect(CSize(-rect.left, -rect.top));
	pOldBitmap = cdc.SelectObject(&bitmap);
	cdc.FillSolidRect(src, RGB(0, 85, 255)); //透明色  
	if (::AlphaBlend == 0)
	{
		dc->BitBlt(rect.left, rect.top, rect.right - rect.left, rect.bottom - rect.top, &cdc, src.left, src.top, SRCINVERT);
	}	else {
		BLENDFUNCTION bf;
		memset(&bf, 0, sizeof(bf));
		bf.SourceConstantAlpha = 0x3f; //透明程度//值越大越不透明  
		bf.BlendOp = AC_SRC_OVER;
		::AlphaBlend(dc->GetSafeHdc(), rect.left, rect.top, rect.right - rect.left, rect.bottom - rect.top,
			cdc.GetSafeHdc(), src.left, src.top, src.right - src.left, src.bottom - src.top, bf);
	}
	cdc.SelectObject(pOldBitmap);
}