With ranking filters, the grey values of the pixels in a defined area around a pixel are collected, sorted by size and ranked. A grey value is then selected from this sorted list to replace the grey value of the current pixel.
The Radius setting defines the size of the area to collect the pixels gray values in.
Tip Bigger filter kernels removes more noise and details from the image.
Rank-order filters belong to the class of non-linear filters in digital image processing. These are filters that cannot be described by a convolution.
With ranking filters, the gray values of the pixels in a defined area around a pixel are collected, sorted by size and ranked. A gray value is then selected from this sorted list to replace the gray value of the current pixel.
The choice of position determines the type of ranking filter. With ascending sorting, you get the:
- Minimum filter, for the minimum gray value, first position in the list
- Median filter, for the gray value in the middle of the list
- Maximum filter, for the maximum gray value, last position in the list.
