DDA Line Algorithm Program in C

Digital Differential Analyzer is an algorithm for drawing straight lines on a computer. This algorithm is very easy as it applies normal mathematical straight line equation formula. But to draw a line on a computer we need to do programs. DDA can be done with C, C++, and JAVA codes, but the main requirement is to do it in a C program.

In the C program of the DDA line, we must have to include graphics.h header file because the output will draw a line on the console.

The slope(m) is calculated by (y2-y1)/(x2-x1) where the two end points of the line are (x1,y1) and (x2,y2).

The algorithm states that if the slope(m) is less than 1 then increase x with 1 and increase y with the slope.  If the slope(m) is greater than 1 then increase x with 1/slope(m) and increase y with 1. And if the slope is equal to 1 then increase both x and y with 1.

The below program is executed in the Turbo C environment. If you run this code in the Turbo C environment then you'll get the optimum output. To run in other compilers you must have to alter initgraph() function's path value.

C Program of DDA Line

#include <graphics.h>

#include <stdio.h>

#include <math.h>

#include <dos.h>

void main( )

{

float x,y,x1,y1,x2,y2,dx,dy,slope;

int i,gd=DETECT,gm;

initgraph(&gd,&gm,"c:\\turboc3\\bgi"); //Initialize the graphics function with path value

printf("Enter the value of x1 and y1 : "); //Take the points

scanf("%f%f",&x1,&y1);

printf("Enter the value of x2 and y2: ");

scanf("%f%f",&x2,&y2);

if(x2<x1 && y2<y1)

{

i=x1;

x1=x2;

x2=i;

i=y1;

y1=y2;

y2=i;

}

dx=abs(x2-x1);

dy=abs(y2-y1);

slope=dy/dx;  //slope m = (y2-y1)/(x2-x1)

x=x1;

y=y1;

if(slope<1) //for slope less than 1 case

{

while(x<=x2) //run the loop until last point's x value is reached

{

putpixel(x,y,5);

x++;

y=y+slope;

delay(100); //delay the line printing by 100 ms

}

}

else if(slope>1) //for slope greater than 1 case

{

while(y<=y2)

{

putpixel(x,y,5);

x=x+(1/slope);

y++;

delay(100);

}

}

else //for slope equal to 1 case

{

while(x<=x2)

{

putpixel(x,y,5);

x++;

y++;

delay(100);

}

}

closegraph(); //close the graphics function

}

The output is as follows:

The above program is the exact representation of the DDA line algorithm. Hope you'll find the program useful. Run the program, enjoy. Don't forget to give your valuable comment on the program and explanations.