DDA Line generation Algorithm in Computer Graphics

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 to implement DDA Line Drawing Algorithm:

1. #include<graphics.h>  
2. #include<conio.h>  
3. #include<stdio.h>  
4. void main()  
5. {  
6.     intgd = DETECT ,gm, i;  
7.     float x, y,dx,dy,steps;  
8.     int x0, x1, y0, y1;  
9.     initgraph(&gd, &gm, "C:\\TC\\BGI");  
10.     setbkcolor(WHITE);  
11.     x0 = 100 , y0 = 200, x1 = 500, y1 = 300;  
12.     dx = (float)(x1 - x0);  
13.     dy = (float)(y1 - y0);  
14.     if(dx>=dy)  
15.            {  
16.         steps = dx;  
17.     }  
18.     else  
19.            {  
20.         steps = dy;  
21.     }  
22.     dx = dx/steps;  
23.     dy = dy/steps;  
24.     x = x0;  
25.     y = y0;  
26.     i = 1;  
27.     while(i<= steps)  
28.     {  
29.         putpixel(x, y, RED);  
30.         x += dx;  
31.         y += dy;  
32.         i=i+1;  
33.     }  
34.     getch();  
35.     closegraph();  
36. }  

Output:

Example: If a line is drawn from (2, 3) to (6, 15) with use of DDA. How many points will needed to generate such line?

Solution: P₁ (2,3)       P₁₁ (6,15)

                x₁=2
                y₁=3
                x₂= 6
                y₂=15
                dx = 6 - 2 = 4
                dy = 15 - 3 = 12
                m = 

For calculating next value of x takes x = x +