**What is Mid Point Circle **Drawing algorithm**?**

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, despite calculating intermediate points as in case of a line segment which actually dependent upon the previous point.

**Properties:**

1) It is an eight symmetry figure.

2) Coordinates or points are calculated using Pythagorean theorem (x-x_centre)^{2}+(y-y_centre)^{2}=r^{2 }

3) Decision parameter decides on which basis further calculations would be made

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

However, Bresenham algorithm came up from Mid Point algorithm.

### Algorithm:

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

4. if d is smaller than 0, then

y=y

x=x+1

d=2x+1

else

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

### C program to draw a circle using Circle Drawing Algorithm

Program:

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 |
#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:

You must be logged in to take the quiz.