The Minimum Blur filter shrinks highlight regions in the image, and broadens darker areas. It works by comparing each pixel to its neighbour and replaces lighter pixels with darker pixels. This is most useful for modifying masks.
About the Minimum Blur filter
This filter can be applied as a non-destructive, live filter. It can be found in the Filters menu, in the Blur category.
Settings
The following settings can be adjusted in the filter dialog:
Radius—controls intensity of the filter. Type directly in the text box or drag the slider to set the value. Dragging to the right on the page allows you to override the maximum value—values above 100 px may affect performance so use with care.
Circular—if this option is off (default), darker regions expand to form square areas. When selected, expanded darker regions are circular.