Re: [Gimp-developer] Overlay Mode - fix.

["Guillermo Espertino (Gez)" <gespertino gmail com>]

El 14/11/12 09:32, yahvuu escribió:
> Am 13.11.2012 18:37, schrieb Michael Natterer:
> > The problem is much bigger. Almost *all* of our layer modes
> > will be "Legacy", and the new modes will operate in linear
> > light. Just adding a hack for overlay is not going to
> > fix the root problem.
> are you referring to technical concerns or rather to UI design challenges?
>
>
> I think the solution that was designed to update the color transfer blend modes
> (#325564) is sustainable here, too:
>
>      Old modes have '(legacy)' appended in layer mode menu and
>      don't show in menu unless an XCF with one of them is openend.
>      They never show in paint menu.
>
> Working with a legacy XCF thus offers some 40 blend modes, which can
> naturally be displayed in two columns, side by side. This is important
> in order to enable manual replacing of the old blend modes on a
> layer-by-layer basis.
>
> The legacy modes are CPU hogs, because they need to apply gamma to
> both inputs and de-gamma the output. I see no way around that.
>
>
> When a legacy XCF gets openend, an automatic conversion to the new blend modes
> can be offered, informing the user that the color appearance might change.
> This needs to be undoable. The notification should be non-intrusive, probably
> similar to Firefoxen's door hangers[1]. I believe a lot of the rationales also
> apply to GIMP. However, this needs to be in line with general GIMP UI (peter?).
>
>
> Writing legacy XCF is clearly an export.
>
>
>
> @Gez: i believe this is mostly in line with your proposal, only that i'd like to
> avoid a modal pop-up on opening the legacy XCF.
I think that a checkbox in the layers panel would be more elegant and 
less of a clutter than adding "legacy blending modes" to the available 
blending modes.
I was thinking about adding it along with the lock buttons. A checkbox 
labeled "legacy mode" that adds the needed gamma correction nodes to all 
the layers and replaces the new overlay for soft-light is all that we need.
I can't see a reason for having legacy blending modes co-existing with 
native. The legacy mode should be only for compatibility.
Users should always use the native mode and only use legacy for the very 
specific cases when old files need to be opened and their appearance has 
to match with other old files.
For artistic purposes, the appearance of the old blending modes should 
be replicated using different tools (probably adjustment layers in the 
future. The non-destructive workflow proposed by Peter should provide 
all the needed tools for that).
Duplicating the number of blending modes available adding the old ones 
is cumbersome and seems quite pointless.

There's an extra use case where legacy mode could be useful, and it's 
working for web mockups. As far as I could see, and the last time I 
asked pippin about this he said the same, since web browsers blend RGBA 
images in gamma-corrected space, it's necessary to design web mockups 
with gamma-corrected alpha overs to match the web appearance.
Currently only alpha-overs are affected, but the web is getting blending 
modes soon in CSS, and apparently they will be also blended in sRGB space.

For that specific case using the legacy mode would be mandatory. But 
again, it doesn't have to co-exist with native. It's switching to a mode 
where everything has to work in the old way (except overlay probably. 
I'm not sure what overlay formula will be used in web browsers).

So, summarizing:
- There's no real need to make new and legacy co-exist. Those seem more 
like exclusive "modes".
- The new mode should be default, and the legacy mode an alternative.
- The current and future web seem to blend RGBA in nonlinear space, so 
having a mode for that could be needed (and in such case the term 
"legacy" isn't entirely accurate).

Regarding the modal popup: this is a very special situation. The user 
has to decide wether to use the native mode or the legacy for the 
imported file. Making that step transparent could mean leaving that 
important difference unnoticed.

Kind regards,
Gez.