[Gimp-developer] [wish] provide transparent color

[Maciej Pilichowski]

Hello,

> From: bgw <west at ieee.org>
> How does "draw with transparency" differ from using eraser tool 
> with x% opacity?

Pencil and eraser are counterparts of course, but I wished for 
transparent color, not just transparent pencil (yes, it exists, and 
it is eraser).

> From: Chris Moller <moller at mollerware.com>
> Doesn't the Eraser Tool do what you need?  

Yes and no, see above.

> (Though maybe some 
> interesting effects could be gotten with an erasing airbrush that
> accumulated in the alpha  channel. 

Exactly! Because once you have transparency as your color you could 
use any tool which works with colors.

> From: Simon Budig <simon at budig.de>
> Well, historically new stuff always had to proove that it is better
> than the old stuff and I personally don't think that is a bad
> thing.

Of course.

> So how do you want to work with transparency? What should happen if
> you have a semi-transparent red and you paint on top of blue?

Good example, because it shows how natural transparent color is. The 
answer: you should get exactly the same effect if you have blue color 
and paint on top of semi-transparent red. It depends on mode and used 
tool.

> Currently it gets blended on top of the blue resulting in some kind
> of violet and that is a widely used feature to do natural looking
> paintings. I understand your proposal, that you actually want to
> have a semi-transparent red in the image after painting?

Both answers are really correct -- see above.

> How is your new feature supposed to interact with tablets with
> varying pressure devices like tablets? Right now you can map the
> pressure information pretty naturally to the opacity. Your
> "replacement" approach for alphacolors would directly influence the
> images alpha channel, making it pretty tricky to lift off the pen
> without leaving a transparent spot (tablets tend to add some events
> at the end et the stroke with very low pressure).

I don't understand that paragraph:
a) the transparent color is not a replacement, I clearly stated this 
in original post, it is addition to the color palette
b) don't pick the transparent color if you don't need it

> How is your "replacement" approach supposed to work with multiple
> layers?

Again, it is not a replacement. 

Honestly, I didn't thought of this issue -- it can be done, but to 
achieve intuitive behaviour it should be well designed not to change 
too many things. So here is the problem now... pity.

> From: David Odin <David at dindinx.org>
>   So your wishes are granted too. There are already tools for that
> in the gimp toolbox: eraser and smudge.

See above.

Kind regards,