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Processing and analysis of biomedical images with the bilateral filter

Cléo Moulin
Semester Master Project

Microengineering section, EPFL

June 2011

 

Abstract

The simultaneous smoothing and edge-preserving property of the bilateral filter makes it really attractive for many image processing applications. The recent discovery of a fast implementation allows a use in real-time applications. During this semester project, novel applications exploiting the edge-preserving quality of the smoother were explored: image source extraction and non-uniform illumination compensation. In daily applications such as reading a barcode, scanning a text or even taking an image through a window, a possible superposition of two sources images (i.e. the front and the back texts) can happen. The extraction of these components, such as the backside text, can often be very useful.

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The non-uniformity of the light distribution can be seen as a problem in applications such as microscopy. A simple thresholding does not allow to separate the zero symbol from its background (See Figure 2). By pre-processing the image (without smoothing the edges), the reconstruction can be improved.

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ImageJ plugins were developed for both applications permitting to work with variable parameters, computing in real-time the output images and the SNR metrics. The possibility to set a gaussian smoothing filter instead of the bilateral allowed a comparison. A study of the bilateral in different configurations gave an understanding on the appropriate configuration of both the spatial and range parameters of the filter to set.

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© 2011 EPFL • webmaster.big@epfl.ch • 11.10.2011