Question

C++画圆（计算机图形学）

VC6.0平台 #include <graphics.h> 库函数下，不能直接调用画圆函数例如：circle()，要求利用圆的八分对称性画点, putpixel(x, y, color); 将坐标进行转换，比如：DOS界面下的坐标只有第一象限，要求原点在界面中间，输入类似（-30，-30）的圆心画的圆也能在结果中显示出来，x,y的点计算中要求用到三角函数，比如cos,sin.
即：三角函数八分画圆，输入的圆心可以为四个象限任意类型的点

Answer 1

#include <math.h>
#include <graphics.h> /*预定义库函数*/
void circlePoint(int x,int y) /*八分法画圆程序*/
{
circle(320 x*20,240 y*20,3);
circle(320 y*20,240 x*20,3);
circle(320-y*20,240 x*20,3);
circle(320-x*20,240 y*20,3);
circle(320-x*20,240 y*20,3);
circle(320-x*20,240-y*20,3);
circle(320-y*20,240-x*20,3);
circle(320 y*20,240-x*20,3);
circle(320 x*20,240-y*20,3);
}
void MidBresenhamcircle(int r) /* 中点Bresenham算法画圆的程序 */
{
int x,y,d;
x=0;y=r;d=1-r; /* 计算初始值 */
while(x<y)
{ circlePoint(x,y); /* 绘制点(x,y)及其在八分圆中的另外7个对称点 */
if(d<0) d =2*x 3; /* 根据误差项d的判断,决定非最大位移方向上是走还是不走 */
else
{ d =2*(x-y) 5;
y--;
}
x ;
delay(900000);
} /* while */
}
main()
{
int i,j,r,graphmode,graphdriver;
detectgraph(&graphdriver,&graphmode);
initgraph(&graphdriver,&graphmode," ");
printf("中点Bresenhamcircle算法画圆的程序\n"); /*提示信息*/
printf("注意 |r|<=11");
printf("\n输入半径值 r:");
scanf("%d",&r);
printf("按任意键显示图形...");
getch();
cleardevice();
setbkcolor(BLACK);
for(i=20;i<=620;i =20) /*使用双循环画点函数画出表格中的纵坐标*/
for(j=20;j<=460;j )
putpixel(i,j,2);
for(j=20;j<=460;j =20) /*使用双循环画点函数画出表格中的横坐标*/
for(i=20;i<=620;i )
putpixel(i,j,2);
outtextxy(320,245,"0"); /*原点坐标*/
outtextxy(320-5*20,245,"-5");circle(320-5*20,240,2); /*横坐标值*/
outtextxy(320 5*20,245,"5");circle(320 5*20,240,2);
outtextxy(320-10*20,245,"-10");circle(320-10*20,240,2);
outtextxy(320 10*20,245,"10");circle(320 10*20,240,2);
outtextxy(320-15*20,245,"-15");circle(320-15*20,240,2);
outtextxy(320 15*20,245,"15");circle(320 15*20,240,2);
outtextxy(320,240-5*20,"-5");circle(320,240-5*20,2); /*纵坐标值*/
outtextxy(320,240 5*20,"5");circle(320,240 5*20,2);
outtextxy(320,240-10*20,"-10");circle(320,240-10*20,2);
outtextxy(320,240 10*20,"10");circle(320,240 10*20,2);
outtextxy(20,10,"The center of the circle is (0,0) "); /*坐标轴左上角显示提示信息*/
setcolor(RED); /*标记坐标轴*/
line(20,240,620,240); outtextxy(320 15*20,230,"X");
line(320,20,320,460); outtextxy(330,20,"Y");
setcolor(YELLOW);
MidBresenhamcircle(r);
setcolor(BLUE); /*绘制圆*/
circle(320,240,r*20);
setcolor(2);
getch();
closegraph();
}