Re: Challenge: Reverse Engineering Standard Filters

["Werner D. Streidt" <wstreidt@bigfoot.de>]

Hi Bill,

>If any of you who wish to develop code for "standard" filters that ship
with
>Photoshop, PSP, etc. want a real challenge, try to duplicate the Photoshop
>Despeckle filter.  It must be simple, because it executes extremely fast.


In the book "Photoshop Filter Finesse", the filter is described as:

"The Despeckle filter detects the edge areas of a selection and retains
those pixels while blurring the areas in between. This filter can clean up
noisy scans while keeping the tight details of an image intact. Multiple
applications of the Desepckle filter can simplify an image somewhat, but
without altering the color the way posterization does."

Has someone tried the technique of erosion/dilatation? (In FiFo in one pass,
in FF probably in two filter passes...)

- Dilatation works like this: in a 3x3 field (used like in the
cnv-fuinction) take the max value.

- Erosion is just the opposite: take the min value

It's maybe worth looking at...

Greetings from Germany,

Werner D. Streidt