DDA Line Drawing Algorithm

In computer graphics, popular algorithms used to generate lines are-

1. Digital Differential Analyzer (DDA) Line Drawing Algorithm
2. Bresenham Line Drawing Algorithm
3. Mid Point Line Drawing Algorithm

In this article, we will discuss about DDA Algorithm.

DDA Algorithm:

Step1: Start Algorithm

Step2: Declare x₁,y₁,x₂,y₂,dx,dy,x,y as integer variables.

Step3: Enter value of x₁,y₁,x₂,y₂.

Step4: Calculate dx = x₂-x₁

Step5: Calculate dy = y₂-y₁

Step6: If ABS (dx) > ABS (dy)
            Then step = abs (dx)
            Else

Step7: x_inc=dx/step
            y_inc=dy/step
            assign x = x₁
            assign y = y₁

Step8: Set pixel (x, y)

Step9: x = x + x_inc
            y = y + y_inc
            Set pixels (Round (x), Round (y))

Step10: Repeat step 9 until x = x₂

Step11: End Algorithm

PROGRAM IN CPP::

#include <graphics.h>
#include <stdio.h>
#include <math.h>
#include <dos.h>
void main( )
{
float x,y,x1,y1,x2,y2,dx,dy,step;
int i,gd=DETECT,gm;
initgraph(&gd,&gm,"c:\\turboc3\\bgi"); //initializing graphics
printf("Enter the value of x1 and y1 : ");
scanf("%f%f",&x1,&y1);
printf("Enter the value of x2 and y2: ");
scanf("%f%f",&x2,&y2);
dx=abs(x2-x1); //calculating constants
dy=abs(y2-y1);
if(dx>=dy) //deciding value of length of line
step=dx;
else
step=dy;
dx=dx/step; //varying distance
dy=dy/step;
x=x1;
y=y1;
i=1;
while(i<=step)
{
putpixel(x,y,5); //ploting graph
x=x+dx; //deciding next point's x cordinate
y=y+dy; //deciding next point's y cordinate
i=i+1;
delay(100);
}
closegraph();
}