A circle can be formed by plotting a set of points or coordinates on the screen which is completely dependent on the radius of that circle, instead of calculating intermediate points as in case of a line segment which actually dependent upon the previous point.
1) It is an eight symmetry figure.
2) Coordinates or points are calculated using Pythagorean theorem (x-x_centre)2+(y-y_centre)2=r2
3) Decision parameter decides on which basis further calculations would be made
x2 + y2 = r2
if d<0 , (x,y ) inside the circle
if d=0,(x,y) is on the boundary of the circle
if d>,(x,y) outside the circle
1. Get radius and coordinates from the user.
2. Find out the decision parameter that decides the nearest point to select using:
d=5/4-r
3. While Y is greater than X do
y=y
x=x+1
d=2x+1
y=y-1
x=x+1
d=d+2x-2y+1
4. Determine and plot the symmetry points for all eight octants.
5. Repeat step 3 and 4, till y>x
Program:
#include<conio.h> #include<graphics.h> void main() { int x,y,x_mid,y_mid,r,d; int g_mode,g_driver=DETECT; clrscr(); initgraph(&g_driver,&g_mode,"C:\\TURBOC3\\BGI"); printf("*********** MID POINT Circle drawing algorithm ********\n\n"); printf("\nenter the coordinates= "); scanf("%d %d",&x_mid,&y_mid); printf("\n now enter the radius ="); scanf("%d",&r); x=0; y=r; d=1-r; do { putpixel(x_mid+x,y_mid+y,1); putpixel(x_mid+y,y_mid+x,1); putpixel(x_mid-y,y_mid+x,1); putpixel(x_mid-x,y_mid+y,1); putpixel(x_mid-x,y_mid-y,1); putpixel(x_mid-y,y_mid-x,1); putpixel(x_mid+y,y_mid-x,1); putpixel(x_mid+x,y_mid-y,1); if(d<0) { d+=(2*x)+1; } else{ y=y-1; d+=(2*x)-(2*y)+1; } x=x+1; }while(y>x); getch(); }
Output:
This post was last modified on April 5, 2021