HOMOMORPHIC_CVIP

homomorphic_cvip() - reduces the effect of illumination variations in a scene while emphasizing the reflectance components.

Contents

SYNTAX

out_img = homomorphic_cvip(input_img,upper,lower,cutoff)

Input Parameters Include :

output Parameter Include :

DESCRIPTION

The function performs Homomorphic Filtering on an input image in order to compress the brightness while enhancing the contrast. The function assumes that the image is a product of the lighting and reflectance components. The basic assumption is that the lighting components are of low spatial fequency in an image. The function has 5 steps:

The filtering operation used in step 3 of the process is essentially a high frequency emphasis process which allows the specification of both the high and low frequency gain.

REFERENCE

1. Scott E Umbaugh. DIGITAL IMAGE PROCESSING AND ANALYSIS: Applications with MATLAB and CVIPtools, 3rd Edition.

EXAMPLE

% Read image

 Input_img = imread('butterfly.tif');

% Upper limit has to be greater than 1.

 upper = 1.5;

% Lower limit has to be less than 1.

 lower = 0.5;

% cutoff frequency

 cutoff = 128;

% calling  function

 outputImage = homomorphic_cvip(Input_img,upper,lower,cutoff);

% Display input image.

 figure;imshow(Input_img);title('Input Image');

% Display output image

 figure; imshow(remap_cvip(outputImage,[]));title('Output Image');

CREDITS

Author: Mehrdad Alvandipour, March 2017
Copyright © 2017-2018 Scott E Umbaugh
For updates visit CVIP Toolbox Website

Published with MATLAB® R2014b