BRESENHAM’S LINE DRAWING ALGORITHM

BRESENHAM’S LINE DRAWING ALGORITHM

Aim :

To write a C program to draw a line using Bresenham’s Algorithm.

Algorithm:

Step 1: Start the program.

Step 2: Input the two endpoints (x1,y1) and (x2,y2).

Step 3: Plot the pixel value (x1,y1) with a specified color.

Step 4: Calculate the value of dx and dy and find the starting value of decision parameter

as dp=2*dy-dx.

Step 5: Calculate the values of s1 and s2 depending on (x1,y1) and (x2,y2) values.

Step 6: If dp<0, the next point to plot is (x,y+s2) and dp=+2*dy.

Step 7: Otherwise the next point to plot is (x+s1,y+s2) and

 dp=dp+2*dx-2*dy.

Step 8: Repeat steps 5 and 6 dx times.

Step 9: Stop the program.

PROGRAM :

#include<stdio.h>

#include<math.h>

#include<conio.h>

#include<graphics.h>

void main()

{

int x1,x2,y1,y2;

int gd=DETECT,gm;

void linebres(int,int,int,int);

printf("Enter the two end points:");

scanf("%d%d%d%d",&x1,&x2,&y1,&y2);

initgraph(&gd,&gm,"");

cleardevice();

linebres(x1,y1,x2,y2);

getch();

line(x1,y1,x2,y2);

getch();

closegraph();

}

void linebres(int x1,int y1,int x2,int y2)

{

int dx=abs(x1-x2),dy=abs(y1-y2);

int p,x,y,i,xend,yend;

if(dx!=0)

{

p=2*dy-dx;

if(x1>x2)

{

x=x2;

y=y2;

xend=x1;

}

else

{

x=x1;

y=y1;

xend=x2;

}

putpixel(x,y,2);

for(i=x;i<xend;i++)

{

x+=1;

if(p<0)

p+=2*dy;

else

p+=2*(dy-dx);

}

putpixel(x,y,2);

}

else

{

p=2*dx-dy;

if(y1>y2)

{

x=x2;

y=y2;

yend=y2;

}

putpixel(x,y,2);

for(i=y;i<yend;i++)

{

y+=1;

if(p<0)

p+=2*dx;

else

{

x+=1;

p+=2*(dx-dy);

}

putpixel(x,y,2);

}

}

}

OUTPUT :

 Bresenham line drawing algorithm

 Enter the co-ordinates

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