Package dev.brachtendorf.jimagehash.hashAlgorithms.filter

Class MedianKernel

  • All Implemented Interfaces:
    Filter, Serializable
    public class MedianKernel
extends NonAveragingKernel
    A median kernel is a non linear filter scanning the image and replacing every value with the median value found in the neighborhood. This median kernel allows a weight matrix to be supplied.

    Example 1D kernel width 5 Kernel and no/uniform mask 

            Values: 5 4 1 3 6
    1 3 4 5 6 During convolution, the kernel looks at the value 1 and replaces it with the value 4 due to it being the median.

    A weight mask [1 2 3 2 1] can give more emphasis on closer pixel values. An intermediary value matrix is calculated: 

     Values * Mask = [5 8 3 6 6]
    3 5 6 6 8 and it is found that the second value is the maximum. Now the unaltered vlaue at position 2 is taken. Therefore the 1 is replaced with the value 4.
    Since:
    2.0.0
    Author:
    Kilian
    See Also:
    MedianKernel, MinimumKernel, Serialized Form

    • Constructor Detail

      • MedianKernel

        public MedianKernel​(int width,
                    int height)
        Create a median kernel with a uniform weight mask (no weighting takes place)
        Parameters:
        width - of the kernel. has to be odd
        height - of the kernel. has to be odd

      • MedianKernel

        public MedianKernel​(double[][] mask)
        Create a kernel with the given masks dimension. The masks acts as weight filter increasing or decreasing the weight of the value during convolution. For an example see the javadoc of the class.
        Parameters:
        mask - weight matrix used to judge which value is the maximum

    • Method Detail

      • calcValue

        protected double calcValue​(byte[][] input,
                           int x,
                           int y)
        Overrides:
        calcValue in class Kernel

      • calcValue

        protected double calcValue​(int[][] input,
                           int x,
                           int y)
        Overrides:
        calcValue in class Kernel

      • calcValue

        protected double calcValue​(double[][] input,
                           int x,
                           int y)
        Overrides:
        calcValue in class Kernel
        Parameters:
        input - array
        x - pixelToLookAt
        y - pixelToLookAt
        Returns:
        convolutedPixel fo this x and y

      • resolveMedian

        protected double resolveMedian​(double[][] values)

      • filter

        public BufferedImage filter​(BufferedImage input)
        Description copied from interface: Filter
        Apply the filter to the input image and return an altered copy
        Specified by:
        filter in interface Filter
        Overrides:
        filter in class Kernel
        Parameters:
        input - the input image to apply the filter on
        Returns:
        the altered image