David Neary wrote:
For the moment, unless I am mistaken, you are the only person to
have stated that they consider the current behaviour wrt
transparency flawed.
I'd just like to say that I somewhat agree with Raphaël.
Using alpha for 'hiding' and unhiding is conceptually wrong,
it's quite equivalent to letting the user take the saturation
knob down to zero and then coming back later, turning up
the saturation again and wondering where the original colours
have gone. I've said it before: an RGBA pixel isn't just an
RGB pixel with a handy auxilliary channel. Alpha is the glass
you draw upon; it accumulates coverage of a certain colour, but
the colour of the glass itself is undefined.
BUT, it's not the user's fault that GIMP hasn't really historically
given this much thought, and has exposed tools and plugins which
more or less pretend that the alpha channel is just another layer
mask. The solution to just about all the 'I want my RGB data
preserved orthogonally to the alpha in my file!' objections is to
load and save the alpha as a layer mask, because that's precisely
what people are wanting the alpha channel to be. That layer masks
aren't quite as convenient to modify as alpha channels (that is to
say, there isn't a tool that implicitly draws onto a layer mask
a la eraser) is one of the reasons that people are going to keep
abusing alpha. Right now probably isn't a good time to go crazy
and change anything to accommodate (I'd still kinda like the
deceptive anti-erase to go away, but don't mind stuff such as
'levels' working on the alpha channel on the understanding that
it's a relatively power-user thing to do and that power-users
understand that the resurrected RGB values of a 0-alpha pixel may
not be as expected).
(For the record, there have existed in the GIMP core for years
some optimizations that skip RGB processing for certain sections
of completely-transparent image regions, which can cause --
albeit under conditions in which the user is least likely to care --
regions of transparency in a composited image to 'go undefined'.
No-one seems to have noticed or at least cared yet.)
Regards,
--Adam
--
Adam D. Moss . ,,^^ adam@xxxxxxxx http://www.foxbox.org/ co:3
Consume Less, Live More
