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Biomedical Imaging Group
Local Normalization
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LOCAL NORM.

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ImageJ's plugin

Local_Norm.jar

Local Normalization

Filter to reduce the effect on a non-uniform illumination

Written by Daniel Sage at the Biomedical Image Group, EPFL, Switzerland

splash image

Outline

The local normalization tends to uniformize the mean and variance of an image around a local neighborhood. This is especially useful for correct non-uniform illumination or shading artifacts.

Reference

Software

Description

The local normalization of f(x,y) is computed as follows:

formula

where:

  • f(x,y) is the original image
  • mf(x,y) is an estimation of a local mean of f(x,y)
  • σf(x,y) is an estimation of the local variance
  • g(x,y) is the output image

diagram

The estimation of the local mean and variance is performed through local spatial smoothing. In this implementation, we use fast recursive Gaussian filters. The parameters of the algorithm are the sizes of the smoothing windows, σ1, and, σ2, which control the estimation of the local mean and local variance, respectively. Often σ2 should be larger than σ1.

Pre-requirement

The software provided here is a plugin for ImageJ, a general purpose image-processing and image-analysis package. It runs also on the image-processing package Fiji. ImageJ has a public domain licence; it runs on several plateforms: Unix, Linux, Windows, and Mac OS X. It doesn't take more than a couple of minutes to install.

Download

Download Local_Norm.jar [Version 03.09.2011]. The plugin consists in one single JAR file; place it into the "plugins" folder of ImageJ. Do not unzip the JAR file.
After restarting ImageJ, you have a new entrie in the Plugin » Filters of ImageJ, which is Local_Normalization.

Instruction
Conditions of use
Matlab version

Matlab version of the Local Normalization, by Guanglei Xiong, 17 Aug 2005 (Updated 07 Sep 2005)

Applet Demonstration

We have also a demonstration of this algorithm running on any browser that supports Java.

Example

Input image

Output image

daniel.sage@epfl.ch • 04.09.2011