Thursday, July 2, 2009


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:

  1. It identifies the dark hair locations by a generalized grayscale morphological closing operation,
  2. It verifies the shape of the hair pixels as thin and long structure, and replace the verified pixels by a bilinear interpolation, and
  3. 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.

Download the Unix version of DullRazor (, 87KB): follow this link.
Download the Windows version of DullRazor (, 327KB): follow this link.

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