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C Program to implement the midpoint circle drawing algorithm

Friday, October 2nd, 2009

C Program to implement the midpoint circle drawing algorithm to draw a circle. Modify the algorithm toimplement specified arc or sector.

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#include <graphics.h>
#include <conio.h>
#include <math.h>
#include <stdio.h>
 
#define PI 3.14
 
float startangle,endangle;
int x,y;
 
int Can_draw( float theta )
{
	if( theta >= startangle && theta<= endangle )
		return 1;
	return 0;
}
 
void Circlepoints(int x,int y,int xc,int yc)
{
	float theta;
	theta = atan( (float)y/x );
	theta = theta * (180/M_PI);
 
if( Can_draw(theta))
		putpixel(xc+x,yc-y,WHITE);
	if( Can_draw(360-theta))
		putpixel(xc+x,yc+y,WHITE);
 
if( Can_draw(90-theta))
		putpixel(xc+y,yc-x,WHITE);
	if( Can_draw(270+theta))
		putpixel(xc+y,yc+x,WHITE);
 
if( Can_draw(180-theta))
		putpixel(xc-x,yc-y,WHITE);
	if( Can_draw(180+theta))
		putpixel(xc-x,yc+y,WHITE);
 
if( Can_draw(90+theta))
		putpixel(xc-y,yc-x,WHITE);
	if( Can_draw(270-theta))
		putpixel(xc-y,yc+x,WHITE);
}
 
void MidPointcircle(int xc,int yc,int rad)
{
	float d = (5/4.0) - rad;
	x=0,y=rad;
 
	while(y>x)
	{
		if(d<0) 
 			d += 2*x+3;
		else 	
			d+=(2*x)-(2*y)+5,y--;
		x++;
		Circlepoints(x,y,xc,yc);
		delay(90);
	}
}
void main()
{
	int gd=DETECT,gm;
	int radius,xc,yc,choice,temp;
	float xstart,ystart,xend,yend;
	initgraph(&gd,&gm,"..\\bgi");
	do
	{
		clrscr();
		cleardevice();
		printf("\n Enter your choice\n");
		printf("\n 1.Draw a Circle\n 2.Draw a Sector\n 3.Draw an Arc\n 4.Exit\n");
		scanf("%d",&choice);
		switch(choice)
		{
			case 1: printf("\n Enter the center:");
				scanf("%d %d",&xc,&yc);
				printf("\n Enter the radius:");
				scanf("%d",&radius);
				cleardevice();
				startangle=0,endangle=360;
				MidPointcircle(xc,yc,radius);
				getch();
				break;
 
			case 2: printf("\n Enter the center:");
				scanf("%d %d",&xc,&yc);
				printf("\n Enter the radius:");
				scanf("%d",&radius);
				printf("\n Enter the startangle:");
				scanf("%f",&startangle);
				printf("\n Enter the endangle:");
				scanf("%f",&endangle);
				cleardevice();
				if(startangle>endangle)
				{
					temp=startangle;
					startangle=endangle;
					endangle=temp;
				}
				MidPointcircle(xc,yc,radius);
				xstart=xc+radius*cos(PI/180*startangle);
				ystart=yc-radius*sin(PI/180*startangle);
				xend=xc+radius*cos(PI/180*endangle);
				yend=yc-radius*sin(PI/180*endangle);
				line(xc,yc,xstart,ystart);
				line(xc,yc,xend,yend);
				getch();
				break;
 
			case 3: printf("\n Enter the center:");
				scanf("%d %d",&xc,&yc);
				printf("\n Enter the radius:");
				scanf("%d",&radius);
				printf("\n Enter the startangle:");
				scanf("%f",&startangle);
				printf("\n Enter the endangle:");
				scanf("%f",&endangle);
				cleardevice();
				if(startangle>endangle)
				{
					temp=startangle;
					startangle=endangle;
					endangle=temp;
				}
				MidPointcircle(xc,yc,radius);
				getch();
				break;
 
		       case 4:  closegraph();
		}
	}while(choice!=4);
}
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Author Name :
Ranjith

Total : 7 Comments

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7 Responses to C Program to implement the midpoint circle drawing algorithm

  1. Mohammad Faisal
    September 25th, 2010 at 7:32 am

    1-Error: Unable to open TCCLASS.LIB

  2. karan
    February 21st, 2011 at 11:48 am

    thanks bro….

  3. Nathulal
    February 21st, 2011 at 12:51 pm

    that’s really coooooooolllllll…….

  4. PRABHAKAR
    May 30th, 2011 at 3:38 pm

    THANKS BROTHERS

  5. kaushal
    September 12th, 2011 at 7:35 pm

    hi
    it is more important to me because it will ask my exam

  6. Roberto
    December 16th, 2011 at 4:33 am

    Great code but how to invert the drawing direction of the arc? It is drawn with “anticlockwise” direction and I would like it to be drawn clockwise.
    Thanks, regards.

  7. Roberto
    December 16th, 2011 at 4:46 am

    Sorry, I forgot to write this: how to make the starting point on the left of the center (now is on the right) and draw the arc (or the circle) following a clockwise direction?

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