Mahotas – Fraction of zeros in image

In this article we will see how we can get the fraction of zeros in the image in mahotas. Fraction of zeros is the percentage amount of statistical data which is zero. It is relevant in statistical models where a significant amount of objects has zero value.

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

mahotas.demos.load('luispedro')

Below is the luispedro image

In order to do this we will use np.mean method

Syntax : np.mean(img==0)



Argument : It takes image object as argument

Return : It returns numpy.float64

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]

Example 1:

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# importing various libraries
import numpy as np
import mahotas
import mahotas.demos
from mahotas.thresholding import soft_threshold
from pylab import imshow, show
from os import path
  
# loading image
f = mahotas.demos.load('luispedro', as_grey = True)
  
  
# showing image
print("Image")
  
# getting fraction of zeros in image
fraction = np.mean(f == 0)
  
print("Fraction of zeros in image: {0}".format(fraction))
imshow(f)
show()
  
  
  
# Transform using D8 Wavelet to obtain transformed image t
t = mahotas.daubechies(f, 'D8')
  
# Discard low-order bits:
t /= 8
t = t.astype(np.int8)
  
  
# getting fraction of zeros in image
fraction = np.mean(t == 0)
  
print("Fraction of zeros in transform (after division by 8): {0}".format(fraction))
  
# showing transformed image
print("Transformed Image")
imshow(t)
show()

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Output :

Example 2:

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# importing required libraries
import mahotas
import numpy as np
from pylab import imshow, show
import os
  
  
# loading iamge
img = mahotas.imread('dog_image.png')
  
# filtering iamge
img = img[:, :, 0]
  
  
# getting fraction of zeros in image
fraction = np.mean(img == 0)
  
print("Fraction of zeros in image: {0}".format(fraction))
imshow(img)
show()
  
  
  
# Transform using D8 Wavelet to obtain transformed image t
t = mahotas.daubechies(img, 'D8')
  
# Discard low-order bits:
t /= 8
t = t.astype(np.int8)
  
  
# getting fraction of zeros in image
fraction = np.mean(t == 0)
  
print("Fraction of zeros in transform (after division by 8): {0}".format(fraction))
  
# showing transformed image
print("Transformed Image")
imshow(t)
show()

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Output :

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