PhotoComiX 10:15pm, 6 December 2009
The layer fade filter seems exactly what i need but i have no idea how wrote
a custom formula for it

The idea is simple

i want confront 2 layer of same size
1 is the edited 2 the original

then replace all pixels that are identical in both layer (that have same color and position ) with transparent pixel
leaving in the merged only the pixels of layer 1 that have some differences, of any kind (position ,color , luminosity, ...)

i do not think i will need a tolerance, a sharp yes/not may suffice
(what identical removed, what with a even minimal difference preserved)


May be possible with a custom formula...?
and well how to write a custom formula ..is explained somewhere ?

PS obviously i will be not offended by something ready for the use
..but still i will like also know more about creating new preset for that filter
admin
Ronounours 7 years ago
Well, to me, it seems this has nothing to do with a classical 'fading' operation.Looks more as a layer 'substract' followed by putting the zero colors to transparency.

This is possible to make such a filter in G'MIC. If I have some time I will try it (but I have already other requests queuing :) )

David.
admin
Ronounours 7 years ago
Well, I added a new filter in G'MIC that does exactly what you want (I think) :

Filter 'Layers/Transparent difference'.
It looks like this :

[https://www.flickr.com/photos/90104203@N00/4165513297/]

Should be available by pressing the 'Refresh' button from the G'MIC dialog window.
Let me know if it is what you whish.

David.
PhotoComiX Posted 7 years ago. Edited by PhotoComiX (member) 7 years ago
Thanks..it seems exactly what i wish
#####################################################
In case you are curious of how intend to use the idea is simple

something as "move last FX" to new layer"
the After and the Before are compared and what changed by last action is moved on a new layer,(..thank again for this GMIC output option..)

..so any kind of editing may be done to correct the last FX (color tool , filters, brush-works ...or whatever else ) without risk to modify other pixels
...and then pasted back

(In Gimp the" before" may be always recovered as new layer with Undo+ copy ... and then Redo+Paste as Layer...)
Groups Beta