GDI+函数之 Region::Complement

TheComplement method updates this region to the portion of the specifiedpath's interior that does not intersect this region.

这个函数用来更新当前Region

用path包含的、同时不在当前区域内的区域（即path区域减去开始region）来更新当前区域。

 

Msdn的例子比较明白：

代码：

{   Graphics graphics(hdc);   SolidBrush solidBrush(Color(255, 255, 0, 0));Pen pen(Color(255,0,255,0));   Point points[] = {      Point(110, 20),      Point(120, 30),      Point(100, 60),      Point(120, 70),      Point(150, 60),      Point(140, 10)};   Rect rect(65, 15, 70, 45);graphics.DrawRectangle(&pen,rect);   GraphicsPath path;   path.AddClosedCurve(points, 6);graphics.DrawPath(&pen,&path);   // Create a region from a rectangle.   Region region(rect);    // Update the region so that it consists of all points inside a path but   // outside the rectangular region.   region.Complement(&path);   graphics.FillRegion(&solidBrush, &region);}

我对它的一个实际应用：

//ptCircleCenter - 扇形的圆心//nRadius - 半径//fAngleStart - 开始的角度//fSweepAngle - 扇形的总角度//rgnPie - 得到的区域void CtestGDIView::GetPieRgnGdiplus(CDC* pDC,CPoint ptCircleCenter,int nRadius,float fAngleStart,float fSweepAngle,__out Region&rgnPie){//第一步，计算矩形POINT topLeft;topLeft.x = (LONG)(ptCircleCenter.x-nRadius);topLeft.y = (LONG)(ptCircleCenter.y-nRadius);Rect rectPie(topLeft.x,topLeft.y,nRadius,nRadius);Graphics graphics(pDC->GetSafeHdc());Pen pen(Color(255,255,0,0));graphics.DrawRectangle(&pen,rectPie);GraphicsPath path;path.AddPie(rectPie,fAngleStart,fSweepAngle);rgnPie.Complement(&path);}

调用：

Rect rect1(0,0,0,0); Region rgn(rect1);CPoint point(200,200);GetPieRgnGdiplus(pDC,point,100,-90,360,rgn); SolidBrush brush(Color(255,255,0,0)); graphics.FillRegion(&brush,&rgn);

Rect rect1(0,0,0,0); Region rgn(rect1);CPoint point(200,200);GetPieRgnGdiplus(pDC,point,100,-90,-90,rgn); SolidBrush brush(Color(255,255,0,0)); graphics.FillRegion(&brush,&rgn);