Enhancement of non-uniform illumination images_study of hep-2 images
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Date
2017-06
Authors
Norhusnai Sakila Mohd Salleh
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Abstract
This project presents a best contrast enhancement method for non-uniform illumination and low contrast medical images. In this study, human epithelial type 2 (HEp-2) cell images were employed as case study. In the most cases, the images captured by digital camera or video camera have non-uniform illumination and poor contrast due to improper lighting, effects from environmental condition and limited performance of the image acquisition devices. These phenomena affect the performance of the cell image which need to be evaluated by medical experts. From the previous research, it is found that the method proposed produce over-enhanced of the original image and tend to produce additional noises. Consequently, the enhancement degraded the contrast of images extremely and produced unnatural look. Hence, the best method is employed to tackles the problems. It is splitting the image histogram into sub-histograms using a mean as a threshold, and replace the cumulative distribution functions with two smooth sigmoid with their origins placed on the median of the sub-histograms. According to the results, the ASIHE and bcnPBDFHE are the best method to enhance the image’s contrastin greyscale and colour format respectively which provides a clearer contrast enhancement and more uniform illumination images.