Maciej Pilichowski (bluedzins@wp.pl) wrote:

Please, provide transparent color or in other words -- treat transparency _also_ as a color.

I don't think that this is a sensible approach in general.

We currently use alpha to do proper antialiasing, compositing existing photos on top of each other and in all of these cases a coupled "alphacolor" (= color + alpha value) would be cumbersome and unhelpful.

Such metaphor is more accurate to real world and thus more appealing to weekend artist (who would like to do some things in simple manner).

Note, that Gimp is not designed with the "weekend artist" in primary focus. But even taking him into account the current model has served us well for the last years and there has been very few discussion about this specific problem, if it cropped up it was in the context of indexed PNGs with "alphacolors" or generating textures for renderers. For the general public the current model seems to generally work and I don't see a compelling reason to change this.

Bye, Simon

On Tue, Sep 23, 2008 at 08:38:53PM +0200, Maciej Pilichowski wrote:

Hello,

I know GIMP has alpha channel and it provides transparency. However it is artificial for me that you have colors and then you have distinct entity -- transparency. It would be useful (and _intuitive_) to have black color, white color, ... and transparent "color", so user could pick up color dialog, choose transparent and paint/draw with transparency.

Such metaphor is more accurate to real world and thus more appealing to weekend artist (who would like to do some things in simple manner).

In the real world I live in, I have yet to see a transparent pencil.

Maciej Pilichowski wrote:

Hello,

I was asked to bring this issue to the ML instead of discussing it on bugzilla so here we go.

Original post: http://bugzilla.gnome.org/show_bug.cgi?id=553003

Please, provide transparent color or in other words -- treat transparency _also_ as a color.

I know GIMP has alpha channel and it provides transparency. However it is artificial for me that you have colors and then you have distinct entity -- transparency. It would be useful (and _intuitive_) to have black color, white color, ... and transparent "color", so user could pick up color dialog, choose transparent and paint/draw with transparency.

Such metaphor is more accurate to real world and thus more appealing to weekend artist (who would like to do some things in simple manner).

Kind regards,

Maciej Pilichowski wrote:

Hello,

I was asked to bring this issue to the ML instead of discussing it on bugzilla so here we go.

Original post: http://bugzilla.gnome.org/show_bug.cgi?id=553003

Please, provide transparent color or in other words -- treat transparency _also_ as a color.

Doesn't the Eraser Tool do what you need? (Though maybe some interesting effects could be gotten with an erasing airbrush that accumulated in the alpha channel. On more thing for the long-term, idle-moment TODO list.)

Maciej Pilichowski (bluedzins@wp.pl) wrote:

From: Simon Budig

But even taking him into account the current model has served us well for the last years and there has been very few discussion about this specific problem, if it cropped up it was in the context of indexed PNGs with "alphacolors" or generating textures for renderers. For the general public the current model seems to generally work and I don't see a compelling reason to change this.

Well, one thing is history -- everything (in general) worked in the past -- why introduce cars when horses... etc etc etc :-)

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.

I guess I have not yet understood what you actually want to achieve.

The second thing is potential benefit -- and I believe less time spent on creating an image _is_ benefit. Note, that it will not introduce new features per se, it only could only change the way you work (if one wishes so). You can work with colors with color tools and you can only work with alpha channel with alpha channel tools. It is narrowing possibilities -- why not pick up brush, shape, pressure and polish a picture edges with transparency (as color)?

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? 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?

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).

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

I see lots of open questions here and I have doubts that your desired workflow is an improvement over the current one. Also I think that most of the tasks you mention in other mails - like cleaning up edges - can nicely be done with the current gimp, provided that you don't need 100% exact control over the alpha values (like the texture guys seem to need it, but they are not the main target audience). So I still don't see the problem here that needs to be solved.

Bye, Simon

On Tue, Sep 23, 2008 at 09:19:09PM +0200, Maciej Pilichowski wrote:

From: David Odin
In the real world I live in, I have yet to see a transparent pencil.

Wish granted -- simply use your finger (I assume you thought of glass painting because it is only good metaphor source for working with alpha channel in the first place).

So your wishes are granted too. There are already tools for that in the gimp toolbox: eraser and smudge.

On Tuesday 23 September 2008, bgw wrote:

How does "draw with transparency" differ from using eraser tool with x% opacity?

You could change the color information at the same places (and less importantly in a single step) you change the alpha information. At least that's how I understand it. Imagine painting with a solvent-diluted color, somehow. It might prove useful, although it might also interfere with current workflows.

My 2¢, Daniel

Simon Budig wrote:

Also I think that most of the tasks you mention in other mails - like cleaning up edges - can nicely be done with the current gimp, provided that you don't need 100% exact control over the alpha values

We do have an old feature request which does deal with different ways of changing alpha by layer masks:
http://bugzilla.gnome.org/show_bug.cgi?id=128118

HTH, Michael

Hi Maciej,

On Wed, Sep 24, 2008 at 3:47 PM, Maciej Pilichowski wrote:

Hello,

From: bgw
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
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
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.

David

Maciej Pilichowski wrote:

So there is obstacle, indeed. And till now I have no idea how to solve this.

Might be a bit of a wild branch on this topic, but I'm wondering if all the effects described here could be implemented as a /subtractive/ process.

I haven't looked at gimp's implementation, but generally speaking colors combine as Cr = Ce * ( 1- o) + Cb * o, where Cr is the resultant color (clamped full saturation of each of it's components), Ce is the existing color, Cb is the brush color, and a is the opacity. What if, instead, you made Cr = Ce * (1 - o) - Cb * o, with Cr clamped at 0? All this doesn't fiddle with the alpha channel at all, but might get the desired effect.

Kind regards,
_______________________________________________ Gimp-developer mailing list
Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer

On Wednesday 24 September 2008, Chris Moller wrote:

Maciej Pilichowski wrote:

So there is obstacle, indeed. And till now I have no idea how to solve this.

Might be a bit of a wild branch on this topic, but I'm wondering if all the effects described here could be implemented as a /subtractive/ process.

I haven't looked at gimp's implementation, but generally speaking colors combine as Cr = Ce * ( 1- o) + Cb * o, where Cr is the resultant color (clamped full saturation of each of it's components), Ce is the existing color, Cb is the brush color, and a is the opacity. What if, instead, you made Cr = Ce * (1 - o) - Cb * o, with Cr clamped at 0? All this doesn't fiddle with the alpha channel at all, but might get the desired effect.

Isn't that pretty much what the 'subtract' mode does? And yes, it doesn't involve the alpha channel.
http://docs.gimp.org/en/gimp-concepts-layer-modes.html

Daniel

Daniel Hornung wrote:

On Wednesday 24 September 2008, Chris Moller wrote:

Maciej Pilichowski wrote:

So there is obstacle, indeed. And till now I have no idea how to solve this.

Might be a bit of a wild branch on this topic, but I'm wondering if all the effects described here could be implemented as a /subtractive/ process.

I haven't looked at gimp's implementation, but generally speaking colors combine as Cr = Ce * ( 1- o) + Cb * o, where Cr is the resultant color (clamped full saturation of each of it's components), Ce is the existing color, Cb is the brush color, and a is the opacity. What if, instead, you made Cr = Ce * (1 - o) - Cb * o, with Cr clamped at 0? All this doesn't fiddle with the alpha channel at all, but might get the desired effect.

Isn't that pretty much what the 'subtract' mode does? And yes, it doesn't involve the alpha channel.
http://docs.gimp.org/en/gimp-concepts-layer-modes.html

Yeah, I expect it's the same function, but adding a transparent layer, painting it, switching to subtract mode, and merging down, is more cumbersome than just painting in subtract mode would be.

cm

Daniel

------------------------------------------------------------------------

_______________________________________________ Gimp-developer mailing list
Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer

On Thursday 25 September 2008, Chris Moller wrote:

Yeah, I expect it's the same function, but adding a transparent layer, painting it, switching to subtract mode, and merging down, is more cumbersome than just painting in subtract mode would be.

The documentation site only refers to those modes as layer modes, whereas you can actually set the mode for any painting tool you use, so it's not really quite as cumbersome.

Excuse the double post  in the first the subject went somehow lost and the rest reformatted in a weird way with question marks filling blank spaces -------------------------------------------------------------------------------------- May be that this long discussion suffers a lack of communication?

to summarize

1 "
brushing a transparent color" is exactly as use the eraser (if there is a alpha channel) Maciej Pilichowski seems agree on this point

2 SO
what is missed
 seems just a equivalent of "AIRbrushing a transparent color",,..a option in the eraser tool to use airbrush instead then a brush will solve that, and for sure will be a cool new feature.

3 May
be is missed, also the possibility to select transparent area as was a color,meaning using the magic wand or the color selector tool..

But since there is "alpha to selection"(=select transparency) that is no too missed... well IS missed its usability since that option is hided in a weird place and is not too clearly labeled( Layer menu really do not seems most intuitive place to search function related to Selections)

For usability may be good add to the "select by color" dialog a checkbox "select transparency",..that checkbox if checked will simply call  "alpha to selection" function and then invert selection(this from a developer's point of view..from average user's point of view that will just "select the transparency " as required)

To my logic (inverted)"alpha to selection" may be well seen as a subset of "select by color" (in this case will be "select by absence of colors " that as concept seems strictly related and may be called more clearly "select transparency"

i believe a "use airbrush" option for eraser tool and a "select transparency" checkbox added to " select by color" will be a nice addition also for who is no much interested to " paint with transparent color"

then a question for Maciej Pilichowski..i understand you well? a
"airbrush-eraser" to allow to "airbrush transparent color" and a more intuitive place and name for "select transparency" will realize your wishes?

A palette with transparent color will be meaningless since if transparent the color will be not visible

 already gimp has gradients with "transparent Color"

___

Hi,

sorry, but your mail is still so badly formatted that I simply refuse to even attempt to read it. Could you please stick to the rules of the mailing-list and send text-only mails instead of this HTML crap with tables? Thank you very much.

Sven

Sven Neumann wrote:

Hi,

sorry, but your mail is still so badly formatted that I simply refuse to even attempt to read it. Could you please stick to the rules of the mailing-list and send text-only mails instead of this HTML crap with tables? Thank you very much.

Please don't think I'm advocating for HTML mail for the list I'm not, just had a brain fart. Does anyone else find it ironic that a mailing list having to do with high quality graphics is text only?

Patrick

On Thu, 25 Sep 2008 12:59:55 -0700 Patrick Horgan wrote:

Hi,

Please don't think I'm advocating for HTML mail for the list I'm not, just had a brain fart. Does anyone else find it ironic that a mailing list having to do with high quality graphics is text only?

Patrick

HTML in mailing list is something really annoying, and it's sad to state that many people still post as HTML. Often this is due to lazy poster which can't override default HTML in composing messages. imho HTML in messages always suck, it's only bearable in RSS feeds.

My two cents Sal