[Gimp-developer] [wish] provide transparent color
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. 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 [EMAIL PROTECTED] So your wishes are granted too. There are already tools for that in the gimp toolbox: eraser and smudge. See above. Kind regards, ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] [wish] provide transparent color
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. David ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] [wish] provide transparent color
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 -- Moller Software Development Services *Christian H. L. Moller* /President/ *Moller Software Development Services, LLC* ** [EMAIL PROTECTED] 919.367.8689 (Voice) www.mollerware.com http://www.mollerware.com 919.367.9097 (Fax) ** ** ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
