Mahotas - Rank Filter - GeeksforGeeks

Mahotas – Rank Filter

Last Updated : 10 Jul, 2020

In this article we will see how we can apply rank filter on image in mahotas. The rank filter, especially filters isolated pixels out, whose intensity differs greatly from that of its immediate neighborhood. Large areas with constant intensity values adjacent to these pixels, as well as edges, are retained after this filter has been used.

In this tutorial we will use “lena” image, below is the command to load it.

mahotas.demos.load('lena')

Below is the lena image

In order to do this we will use mahotas.rank_filter method

Syntax : mahotas.rank_filter(img, neighbour, rank)

Argument : It takes image object and two integer as argument

Return : It returns image object

Note : Input image should be filtered or should be loaded as grey

In order to filter the image we will take the image object which is numpy.ndarray and filter it with the help of indexing, below is the command to do this

image = image[:, :, 0]

Below is the implementation

# importing required libraries 
import mahotas 
import mahotas.demos 
from pylab import gray, imshow, show 
import numpy as np 
import matplotlib.pyplot as plt 
    
# loading iamge 
img = mahotas.demos.load('lena') 
    
# filtering image 
img = img.max(2) 
  
print("Image") 
    
# showing image 
imshow(img) 
show() 
  
# neighbour pixel 
neighbour = 3
  
# rank 
rank = 2
  
# applaying rank filter 
new_img = mahotas.rank_filter(img, neighbour, rank) 
   
  
# showing image 
print("Rank Filter") 
imshow(new_img) 
show() 

Output :

Image

Rank Filter

Another example

# importing required libraries 
import mahotas 
import numpy as np 
from pylab import gray, imshow, show 
import os 
import matplotlib.pyplot as plt 
   
# loading iamge 
img = mahotas.imread('dog_image.png') 
  
  
# fltering image 
img = img[:, :, 0] 
    
print("Image") 
    
# showing image 
imshow(img) 
show() 
  
# neighbour pixel 
neighbour = 3
  
# rank 
rank = 2
  
# applaying rank filter 
new_img = mahotas.rank_filter(img, neighbour, rank) 
   
  
# showing image 
print("Rank Filter") 
imshow(new_img) 
show() 