[PD] pd/gem per-pixel image manipulation

[Martin Leopold Grödl]

hi everybody, i want to do per pixel image manipulation in gem (running 
pd.extended 0.39-3).
so far i've been trying pix_dump with a lister and then until with 
packel to access individual rgba values in a loop. after i do the 
manipulations i accumulate them back into a list using repack and send 
it to pix_set.

it all works out pretty smooth. only problem is the list that gets sent 
to pix_set somehow seems to get one float prepended, which effectively 
shifts all the rgba-values one step and messes up the colors.

any advice/examples on a correct pix_dump / pix_set setup? ...any other 
solutions?

thx,
martin