Recently, there has been an increase in the number of studies using image processing techniques to analyze melanocytic lesions for atypia and possible malignancy, and for total-body mole mapping. Such lesions, however, can be partially obscured by body hair; and, to date, no study has fully addressed the problem of human hair occluding imaged lesions. In a previous study we designed an automatic segmentation program to differentiate skin lesions from normal healthy skin. Our program performed well with most images — the exception being images where dark thick hair covers part of the lesions. Dark hair confused the program which resulted in unsatisfactory segmentation results.
Presented here is a method to remove hair from images using a pre-processing program called DullRazor. DullRazor performs the following steps:
- It identifies the dark hair locations by a generalized grayscale morphological closing operation,
- It verifies the shape of the hair pixels as thin and long structure, and replace the verified pixels by a bilinear interpolation, and
- It smooths the replaced hair pixels with an adaptive median filter.
The algorithm has been implemented in C on a SunOS 4.x workstation. (The program can be run on Sun Solaris workstations as well.) It has been tested on real nevi images with satisfactory results. Figure 1. shows a lesion covered by thick hair and Figure 2. shows the result with hair removed. The man.txt file provides more details.
DullRazor can be downloaded and used without fee for non-commerical purpose. The full license is included in the download.