Hi Maciej,

On Wed, Sep 24, 2008 at 3:47 PM, Maciej Pilichowski <[EMAIL PROTECTED]> wrote:
> Hello,
>> From: bgw <[EMAIL PROTECTED]>
>> 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 <[EMAIL PROTECTED]>
>> 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 <[EMAIL PROTECTED]>
>> 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.
There is no way to achieve the effect you describe without it being a
replacement effect.
This is because it violates the normal behaviour of alpha, which is a
specifier of opacity for a particular color; without a color, an alpha
value is meaningless.

Also, the 'semitransparent color' usage and the 'erasing' usage are
directly contradictory. Semitransparent color could work in a fairly
normal way, erasing would have to replace the underlying pixel values
rather than blending them.

If you want to develop this idea further -- personally I think it's an
interesting idea -- I believe it will be necessary to discard the
notion of a 'color' which is fully transparent, ie. the notion of
being able to erase just by 'color' adjustment.

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