Implementation of DDA Line Drawing Algorithm

Here is a source code in traditional Turbo C that makes use of old DOS mode graphics to implement the digital differential analyzer.

Digital Differential Analyzer

Algorithm

1) Input two points (x1, y1) & (x2, y2).
2) Determine the differences dx = x2 - x1 and dy = y2 - y1.
3) Choose step size as the bigger value between the absolute values of dx and dy.
4) Determine x-increment = dx/step_size and y-increment = dy/step_size.
5) Start from (x0, y0) = (x1, y1).
6) For i -> 0 to stepsize:
    a) draw pixel at (x_i, y_i)
    b) set x_k = x_k + x-increment
    b) set y_k = y_k + y-increment

Source Code

#include <stdio.h>
#include <conio.h>
#include <graphics.h>
#include <math.h>

int main()
{
 int gd = DETECT, gm;
 int x1, y1, x2, y2, dx, dy, stepsize;
 float xinc, yinc, x, y;
 int i;
 printf("Enter x1, y1: ");
 scanf("%d %d", &x1, &y1);
 printf("Enter x2, y2: ");
 scanf("%d %d", &x2, &y2);
 dx = x2 - x1;
 dy = y2 - y1;
 stepsize = (abs(dx) > abs(dy))?abs(dx):abs(dy);
 xinc = dx/(float)stepsize;
 yinc = dy/(float)stepsize;
 x = x1;
 y = y1;
 initgraph(&gd, &gm, "C:\\TC\\BGI");
 putpixel(x, y, WHITE);
 delay(10);
 for (i = 0; i < stepsize; i++)
 {
  x += xinc;
  y += yinc;
  putpixel(x, y, WHITE);
  delay(50);
 } 
 getch();
 closegraph();
 return 0;
}

Make sure to provide an appropriate path for graphics library.