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Edit Alpha as Mask

This discussion is connected to the gimp-developer-list.gnome.org mailing list which is provided by the GIMP developers and not related to gimpusers.com.

This is a read-only list on gimpusers.com so this discussion thread is read-only, too.

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Edit Alpha as Mask Joao S. O. Bueno 10 Sep 18:53
20030909194323.CA1311059B@l... 07 Oct 20:22
  Edit alpha as mask Jean-Christophe Dubacq 09 Sep 23:01
   Edit alpha as mask Sven Neumann 10 Sep 02:24
Jean-Christophe Dubacq
2003-09-09 23:01:40 UTC (over 21 years ago)

Edit alpha as mask

On Tue, Sep 09, 2003 at 12:43:23PM -0700, gimp-developer-request@lists.xcf.berkeley.edu wrote:

Seems that what you want to do is better done with a layer mask, as you've already been explained. But if you already have the alpha channel and want to convert it to a mask, I can offer you two solutions: 1. Follow these steps:

[...]

2. Copy the following script (which uses an undocumented hack and may =

[...]

Thank you. This is exactly what I wanted. All my tries with gimp-1.3.19 trying to use the 'Alpha' channel (and not a mask) were unsuccessfull.

There is no way of painting (or for the matter pasting into) the alpha layer. Creating mask--deleting alpha--editing mask--apply mask is what I used (not with a script), but it is quite cumbersome, and this is why I did post to gimp-devel: so that there may be a possibility to directly edit the alpha channel of a layer (as there is the possibility of directly painting onto only the blue layer, or red or green) in the future. I certainly meant no offense.

Meanwhile, your script will serve my needs. I do very small icons, and like to set transparency pixel by pixel.

Sven Neumann
2003-09-10 02:24:24 UTC (over 21 years ago)

Edit alpha as mask

Hi,

Jean-Christophe Dubacq writes:

I did post to gimp-devel: so that there may be a possibility to directly edit the alpha channel of a layer (as there is the possibility of directly painting onto only the blue layer, or red or green) in the future.

Please note that in 1.3 the alpha channel is treated just like the color channels. What you ask for above would be a different thing. If for example you switch off all channels but the blue one, all paint operations will only affect the blue channel. This doesn't change the way the paint tools work, it only locks the pixel data of all channels but the blue one. For the alpha channel the behaviour is just the same. Switching off all other channels keeps you from changing the color channels but still painting increases the opacity, erasing decreases it.

Sven

Joao S. O. Bueno
2003-09-10 18:53:52 UTC (over 21 years ago)

Edit Alpha as Mask

I failed to send this to the list yesterday. I have a proposal to the matter of editting the alpha channel as mask, as follows:

-------- Original Message -------- Subject: Re: [Gimp-developer] Edit Alpha as Mask Date: 10 Sep 2003 13:04:27 +0200
From: Sven Neumann
To: Joao S. O. Bueno
References:

Hi,

"Joao S. O. Bueno" writes: >(...)

Yup...
Instead of changing the alpha channel when adding a layer mask, create an option besides "apply layer mask". I think "Replace layer alpha with mask" would be descriptive enough and add the needed functionality,

You are bringing up a completely new point here and I think you want to repost this to the list.

Sven --
J.S.
->