How make from 3 chanel to 4 for...

Hi,



I am new to Photoshop SDK plugin programming.



I want to write a filter, which will modify some (but not all) pixels transparently.



My input a rectangle selection with only 3 (rgb) chanels

My output 4 chanels with rgba.



I can't change the filterCase or number of planes...



Can you give me some suggestions that what can I do?

What I need change in PiPL? or in software?

Or can I find a good sample?



Thanks for your help,

Felix