The Box Blur filter blurs an image based on the average colour of neighbouring pixels. At high radius levels, this results in an obvious 'box' effect. At lower radius levels, it results in an effect similar to Gaussian Blur.
This filter can be found in the Filters panel, in the Blurs category.
This filter can be applied as a non-destructive, live filter.
The following settings can be adjusted on the vertical slider:
The following settings can be adjusted on the context toolbar: