On 10/30/18 11:01 AM, Julien Hardelin wrote: > Hi all, > > I don't understand the "Alpha percentile" option in Median Blur filter. > > Is this "alpha" a term related to statistics or to transparency ? I > can't built an example of this option. By default, the Median Blur filter finds the median value at the neighborhood of each pixel. In spite of its name, the filter can actually find *any* arbitrary percentile, not just the median (i.e., the 50th percentile). The "Percentile" parameter controls the percentile used for the color components, and the "Alpha percentile" parameter separately controls the percentile used for the alpha component. In other words, "alpha" is related to transparency in this context. To see the effect of this parameter, you need an image with transparency -- if the alpha channel is opaque everywhere, the result will also be fully opaque, regardless of the percentile. Much like the color "Percentile" parameter, for which lower values shift the image toward darker tones and higher values toward brighter ones, lower values for the "Alpha percentile" parameter shift the image toward more transparency, and higher values shift the image toward more opacity, where a value of 50% is balanced. Roughly speaking, values less than 50% make the opaque regions of the image smaller, while values greater than 50% make the opaque regions of the image larger. -- Ell _______________________________________________ gimp-docs-list mailing list gimp-docs-list@xxxxxxxxx https://mail.gnome.org/mailman/listinfo/gimp-docs-list
