Rank filter

Use the Process > Smoothing Filters > Rank... command to reduce the noise in an image.

The rank filter, especially filters isolated pixels out, whose intensity differs greatly from that of its immediate neighborhood. Large areas with constant intensity values adjacent to these pixels, as well as edges, are retained after this filter has been used. In contrast to filtering with a mean filter, such as the NxN filter, the filtered image thus loses none of its original clarity.

The dialog box that is opened when you use an image processing operation is made up in the same way for every operation. Click here to switch to a description of this dialog box.

Parameters for the Rank filter

Enter the diameter of the adjacent area in units of pixels in the Size field. The larger the diameter, the larger the disturbances can be that will be suppressed by the Rank filter.

Enter by which intensity value you want to replace the central pixel of the adjacent area in the Rank field. At a rank of 0, the central pixel will always be replaced by the lowest intensity value of its adjacent area. At a rank of 100, by the highest intensity value. At a rank of 50, the central pixel will be set at the mean intensity value of the ranking sequence. The preset value is 50.

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