Bresenham Line Drawing Algorithm Explained with Examples
Bresenham Line Drawing Algorithm is a method used to generate points between starting and ending coordinates to draw lines efficiently. This algorithm involves calculating parameters, decision parameters, and iteratively finding points along the line. Two example problems are provided with step-by-step solutions showcasing the application of the Bresenham Line Drawing Algorithm.
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Bresenham Line Drawing Algorithm Given the starting and ending coordinates of a line, Bresenham Line Drawing Algorithm attempts to generate the points between the starting and ending coordinates. Procedure- Given- Starting coordinates = (X0, Y0) Ending coordinates = (Xn, Yn) The points generation using Bresenham Line Drawing Algorithm involves the following steps
Step-01: Calculate X and Y from the given input. These parameters are calculated as- X = Xn X0 Y =Yn Y0 Step-02: Calculate the decision parameter Pk. It is calculated as- Pk= 2 Y X Step-03: Suppose the current point is (Xk, Yk) and the next point is (Xk+1, Yk+1). Find the next point depending on the value of decision parameter Pk. Follow the below two cases-
Problem-01: Calculate the points between the starting coordinates (9, 18) and ending coordinates (14, 22). Solution Given Starting coordinates = (X0, Y0) = (9, 18) Ending coordinates = (Xn, Yn) = (14, 22) Step-01: Calculate X and Y from the given input. X = Xn X0= 14 9 = 5 Y =Yn Y0= 22 18 = 4 Slope = Y / X = 4/5=0.8 <1
Step-02: Calculate the decision parameter. P0 = 2 Y X = 2 x 4 5 = 3 So, decision parameter Pk= P0= 3 Step-03: As Pk>= 0, so case-02 is satisfied. Thus, Pk+1= Pk+ 2 Y 2 X = 3 + (2 x 4) (2 x 5) = 1 Xk+1= Xk+ 1 = 9 + 1 = 10 Yk+1= Yk+ 1 = 18 + 1 = 19
Similarly, Step-03 is executed until the end point is reached or number of iterations equals to 4 times. As Pk>= 0, so case-02 is satisfied. Thus, Pk+1= Pk+ 2 Y 2 X = 1 + (2 x 4) (2 x 5) = -1 Xk+1= Xk+ 1 = 10+ 1 = 11 Yk+1= Yk+ 1 = 19 + 1 = 20 As Pk<0, so case-01 is satisfied. Thus, Pk+1= Pk+ 2 Y = -1 + (2 x 4) = 7 Xk+1= Xk+ 1 = 11 + 1 = 12 Yk+1= 20
Problem 2: Calculate the points between the starting coordinates (20, 10) and ending coordinates (30, 18).