计算机图形学——圆的绘制

根据圆的扫描转换
利用Bresenham算法原理：利用在圆上的8个点

void CCircleView::OnDraw(CDC* pDC)
{
	CCircleDoc* pDoc = GetDocument();
	ASSERT_VALID(pDoc);
	// TODO: add draw code for native data here
	myCircle(400,200,100);
}

void CCircleView::myCircle(int x0, int y0, int r)
{
	int x=0,y=r;
	float d=(float)1.25-r;
	CDC *pDC=GetDC();
	while(x<=y)
	{	
		pDC->SetPixel (x+x0,y+y0,RGB(223,255,0));
    	pDC->SetPixel (-x+x0,y+y0,RGB(0,255,0));
	    pDC->SetPixel (-y+x0,x+y0,RGB(255,0,0));
		pDC->SetPixel (-y+x0,-x+y0,RGB(0,0,255));
		pDC->SetPixel (x0-x,-y+y0,RGB(233,244,0));
		pDC->SetPixel (x0+x,-y+y0,RGB(255,223,0));
		pDC->SetPixel (x0+y,-x+y0,RGB(255,0,255));
		pDC->SetPixel (x0+y,x+y0,RGB(255,255,0));
		
		if(d<0)
		{   
			d=d+2*x+3;
	       	x++;
		   // y--; 
		}
		else
		{    
			d=d+2*x-2*y+5; 
			x++;
			y--;
		}
		
	}
    ReleaseDC(pDC);
}

在C…View头文件中相应的函数中增加参数
通过改变d<0和d>=0的条件可以形成不同的形状
(1)d<0 x++
d>=0 x++;y–;

(2) d<0 x++;y–
d>=0 x++;y–

(3) d<0 x++;
d>=0 x++;

(4) d<0 x++;y–;
d>=0 x++;

(5) d<0 y–;
d>=0 x++;

(6) d<0 y–;
d>= 0 y–;

(7) d<0 x++;
d>=0 y–;

(8) d<0 x++;y–;
d>=0 y–;