近些天写了一些关于计算机图形学的算法和源代码!
如果喜欢转载请标明出处：并非菜鸟的博客http://blog.csdn.net/syx1065001748
源代码：源代码在这里!
关于中点画圆，大家都知道是根据圆的8分对称性质，然后画出1/8圆之后再进行对称画点，就可以得到完整的圆了。首先给出圆的一般算法，是使用中点画圆的统法，在原点画圆！然后进行平移来得到!
下边是使用橡皮筋的方法实现的画圆方法！
void MidPointCircle(int x0,int y0,int x1,int y1) //(x0,y0)鼠标左键落下的点和(x1,y1)MouseMove的点
{
CClientDC dc(this);
int oldmode=dc.SetROP2(R2_NOTXORPEN);
int r=(max(x1,x0)-min(x1,x0))/2;//求的圆心
int x,y,cx,cy;
cx=(x1+x0)/2;//圆心X坐标
cy=(y0+y1)/2;//圆心Y坐标
float d; //判别D
x=0;
y=r;
d=1.25-r;//避免取反无法显示</span>
dc.Ellipse(x+cx-int(gaps/2.0),y+cy+int(gaps/2.0),x+cx+int(gaps/2.0),y+cy-int(gaps/2.0));
dc.Ellipse(y+cx-int(gaps/2.0),x+cy+int(gaps/2.0),y+cx+int(gaps/2.0),x+cy-int(gaps/2.0));
dc.Ellipse(x+cx-int(gaps/2.0),-y+cy+int(gaps/2.0),x+cx+int(gaps/2.0),-y+cy-int(gaps/2.0));
dc.Ellipse(-y+cx-int(gaps/2.0),x+cy+int(gaps/2.0),-y+cx+int(gaps/2.0),x+cy-int(gaps/2.0));
while(x<y)
{
if(d<0)
d=d+2*x+3;
else
{
d=d+2*(x-y)+5;
y--;
}
x++;
CirclePoint(cx,cy,x,y);
}
dc.SetROP2(oldmode);
}
void CirclePoint(int cx,int cy,int x, int y)//辅助画点
{
CClientDC dc(this);
int oldmode=dc.SetROP2(R2_NOTXORPEN);
if(y==x)
{
dc.SetPixel(x+cx,y+cy,RGB(255,255,0));
dc.SetPixel(x+cx,-y+cy,RGB(255,255,0);
dc.SetPixel(-x+cx,-y+cy,RGB(255,255,0));
dc.SetPixel(-x+cx,y+cy,RGB(255,255,0));
}
else if(x!=y+gaps)
{
dc.SetPixel(x+cx,y+cy,RGB(255,255,0));
dc.SetPixel(-x+cx,y+cy,RGB(255,255,0));
dc.SetPixel(x+cx,-y+cy,RGB(255,255,0));
dc.SetPixel(y+cx,x+cy,RGB(255,255,0));
dc.SetPixel(-y+cx,x+cy,RGB(255,255,0));
dc.SetPixel(-y+cx,-x+cy,RGB(255,255,0));
dc.SetPixel(-x+cx,-y+cy,RGB(255,255,0));
dc.SetPixel(y+cx,-x+cy,RGB(255,255,0));
}
dc.SetROP2(oldmode);
}
以上是画圆算法的一般情况其中CX和CY分别是经过圆心（0,0），平移过后的圆心也就是偏移量!然后给一段关于如何将画圆显示在自己设置的像素坐标系中
以上是效果图
MidPointCircle(int x0,int y0,int x1,int y1) //(x0,y0)和(x1,y1)两个点数遍落下两个点
{
CClientDC dc(this);
int oldmode=dc.SetROP2(R2_NOTXORPEN);
int r=Ajust((maxn(x1,x0)-mine(x1,x0))/2,gaps);
int x,y,cx,cy;
cx=Ajust((x1+x0)/2,gaps);
cy=Ajust((y0+y1)/2,gaps);
float d;
x=0;
y=r;
d=1.25-r;
dc.Ellipse(x+cx-int(gaps/2.0),y+cy+int(gaps/2.0),x+cx+int(gaps/2.0),y+cy-int(gaps/2.0));
dc.Ellipse(y+cx-int(gaps/2.0),x+cy+int(gaps/2.0),y+cx+int(gaps/2.0),x+cy-int(gaps/2.0));
dc.Ellipse(x+cx-int(gaps/2.0),-y+cy+int(gaps/2.0),x+cx+int(gaps/2.0),-y+cy-int(gaps/2.0));
dc.Ellipse(-y+cx-int(gaps/2.0),x+cy+int(gaps/2.0),-y+cx+int(gaps/2.0),x+cy-int(gaps/2.0));
while(x<y)
{
if(d<0)
d=d+2*x+3;
else
{
d=d+2*(x-y)+5;
y-=gaps;
}
x+=gaps;
CirclePoint(cx,cy,x,y);
}
dc.SetROP2(oldmode);
}
CirclePoint(int cx,int cy,int x, int y)
{
CClientDC dc(this);
int oldmode=dc.SetROP2(R2_NOTXORPEN);
if(y==x)
{
dc.Ellipse(x+cx-int(gaps/2.0),y+cy+int(gaps/2.0),x+cx+int(gaps/2.0),y+cy-int(gaps/2.0));
dc.Ellipse(x+cx-int(gaps/2.0),-y+cy+int(gaps/2.0),x+cx+int(gaps/2.0),-y+cy-int(gaps/2.0));
dc.Ellipse(-x+cx-int(gaps/2.0),-y+cy+int(gaps/2.0),-x+cx+int(gaps/2.0),-y+cy-int(gaps/2.0));
dc.Ellipse(-x+cx-int(gaps/2.0),y+cy+int(gaps/2.0),-x+cx+int(gaps/2.0),y+cy-int(gaps/2.0));
}
else if(x!=y+gaps)
{
dc.Ellipse(x+cx-int(gaps/2.0),y+cy+int(gaps/2.0),x+cx+int(gaps/2.0),y+cy-int(gaps/2.0));
dc.Ellipse(-x+cx-int(gaps/2.0),y+cy+int(gaps/2.0),-x+cx+int(gaps/2.0),y+cy-int(gaps/2.0));
dc.Ellipse(x+cx-int(gaps/2.0),-y+cy+int(gaps/2.0),x+cx+int(gaps/2.0),-y+cy-int(gaps/2.0));
dc.Ellipse(y+cx-int(gaps/2.0),x+cy+int(gaps/2.0),y+cx+int(gaps/2.0),x+cy-int(gaps/2.0));
dc.Ellipse(-y+cx-int(gaps/2.0),x+cy+int(gaps/2.0),-y+cx+int(gaps/2.0),x+cy-int(gaps/2.0));
dc.Ellipse(-y+cx-int(gaps/2.0),-x+cy+int(gaps/2.0),-y+cx+int(gaps/2.0),-x+cy-int(gaps/2.0));
dc.Ellipse(-x+cx-int(gaps/2.0),-y+cy+int(gaps/2.0),-x+cx+int(gaps/2.0),-y+cy-int(gaps/2.0));
dc.Ellipse(y+cx-int(gaps/2.0),-x+cy+int(gaps/2.0),y+cx+int(gaps/2.0),-x+cy-int(gaps/2.0));
}
//*/
dc.SetROP2(oldmode);
}
Ajust(int x,int gaps) //调整x,y到自己的方格点上！ gaps是方格大小!
{
if(x%gaps>gaps/2)
x=int(x/gaps+1)*gaps;
else
x=int(x/gaps)*gaps;
return x;
}
