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Sigma Filter

    Name

    Sigma Filter

    Software

    ImageJ

    Author

    Michael Schmid and Tony Collins

    Source

    Sigma_Filter_Plus.java

    Status

    1st version

    Category

    Filtering

    Purpose

    This plugin implement a spatial filter similar to the mean filter. Its particularity is that it tries to preserve edges and to discard outliers by selecting what pixels to include in the mean.

    Documentation

    This filter is based on the algorithm described in the following paper:

    TODO citation: Lee, Jong-Sen; , ; , (), Digital image smoothing and the sigma filter, Computer vision, graphics, and image processing, ISSN 0734-189X

    From the website:

    “The filter smooths an image by taking an average over the neighboring pixels, but only includes those pixels that have a value not deviating from the current pixel by more than a given range. The range is defined by the standard deviation of the pixel values within the neighborhood (“Use Pixels Within … Sigmas”).

    If the number of pixels in this range is too low (less than “Minimum Pixel Fraction”), averaging over all neighboring pixels is performed. With the “Outlier Aware” option, averaging over all neighboring pixels excludes the center pixel. Thus, outliers having a value very different from the surrounding are not included in the average and, thus, completely eliminated.”