The Bresenham algorithm is another incremental scan conversion algorithm. It is useful alternative for the DDA The big advantage of this algorithm is that it uses only integer calculations

1. Bresenham Line
Drawing Algorithm
බ්‍රිසන්හෙම් හේ සරල හේඛා නිේමාණය
සඳො වූ ඇල්හ ොරිතමය

2. The Bresenham algorithm is another incremental
scan conversion algorithm. It is useful alternative for
the DDA
The big advantage of this algorithm is that it uses
only integer calculations
Let’s take following example
If starting point is (2,2)and ending point of line is
(7,4) calculate the first 3 points of the line by using
Bresenham algorithm

3. First of all we take first plot of the above line
as (2,2)
Then we need to calculate constant of
following
Δx => 7-2=5
Δy => 4-2=2
2Δy => 4
2Δx =>10
2Δy – Δx => 4-5=-1
2Δy -2Δx=> 4-10=-6

4. Then we need to find p1 for plot the second plot of
the line
P1= 2Δy – Δx
P1= 4-5=-1
P1<0 then we are not increasing y from
1(always x increase from 1)
Second plot is (3,2)
Use to find P1

5. Then we need to find p2 for plot the second plot of
the line
When the P1 is less than 1 we use following
algorithm to find the next plot
P2= P1 +2Δy
P2= -1 + 4=3
In this time P2>0 then we increase y from
1(always x increase from 1)
Second plot is (4,3)
If P1<0 we use flowing equation
to find P2

6. Then we need to find p3 for plot the third plot of
the line
When the P2 >0 we use following algorithm
to find the next plot
P3= P2 +2Δy - 2Δx
P3= 3+ 4-10=-3
In this time P3<0 then we are not increasing
y from 1(always x increase from 1)
Third plot is (5,3)
If P2>0 we use flowing equation
to find P3

7. 10 2 3 4 5 6 7
1
2
3
4
5
6
7

8. If we take it up to final plots our plots will show
as
(2,2)
(3,2)
(4,3)
(5,3)
(6,4)
(7,4)