DDA line algorithm |line drawing algorithm

DDA (digital deferential analyzer)

1.  Read the line points (x1,y1 , x2,y2) such that they are not equal (if they are equal then plot that point and exit).
2.  dx= |x2-x1| , dy = |y2-y1|
3.  if dx >= dy then length= dx else length = dy
4.  dx= (x2-x1)/length , dy= (y2-y1)/length this makes either dx or dy=1.
5.  x=x1+0.5*sign(dx) , y=y1+0.5*sign(dy).
6.  i=1(begins the loop) . In this loop points are poltted.
7.  while(i<=length)

           {
           plot(Interger(x)= Integer (y))
           x=x+dx
           y= y+dy
           i=i+1
           }
      8. stop.

         

Example of DDA line drawing algorithm.
Suppose we want to draw a line starting at pixel (2,3) and ending at pixel (12,8).
 num steps= 12-2=10
 x inc = 10/10=1.0
 y inc = 5/10= 0.5

t	x	R(x)	R(y)
0	2	2	3
1	3	3	4
2	4	4	4
3	5	5	5
5	7	7	6
6	8	8	6
7	9	9	7
8	10	10	7
9	11	11	8
10	12	12	8

Posted in DDA line algorithm, line algorithm, line drawing algorithm