RSS/Atom feed Twitter
Site is read-only, email is disabled
  1. Chat
  2. Useful links
  3. Polls

Featured content

feature request: alpha level

This discussion is connected to the gimp-user-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.

4 of 4 messages available
Toggle history

Please log in to manage your subscriptions.
feature request: alpha level Alex Vergara Gil 22 Jul 13:38
  feature request: alpha level Daniel Hornung 22 Jul 19:34
   feature request: alpha level Ofnuts 22 Jul 20:45
    feature request: alpha level Alex Vergara Gil 23 Jul 14:07
Alex Vergara Gil
2013-07-22 13:38:00 UTC (over 11 years ago)

feature request: alpha level

Hello GIMP developers:

I am working on a project where I need to set all pixels below a level as alpha channel, is there a quick way to achieve this? The level can be both set a priori or adjusted dinamically, the second way is prefered. Right now my workflow includes: 1. duplicate layer.
2. use color level in duplicate layer, in menu COLOR -> LEVEL. 3. add alpha mask to original layer
4. copy duplicate layer into the alpha mask of the original. 5. delete duplicate layer.
6. If result is not ok then return to 1. As you can see this workflow is a headache, specially point 6 which is often achieved. Any thoughts

Alex

Daniel Hornung
2013-07-22 19:34:11 UTC (over 11 years ago)

feature request: alpha level

On Monday, 22. July 2013 08:38:00 Alex Vergara Gil wrote:

Hello GIMP developers:

I am working on a project where I need to set all pixels below a level as alpha channel, is there a quick way to achieve this? The level can be both set a priori or adjusted dinamically, the second way is prefered. Right now my workflow includes: 1. duplicate layer. 2. use color level in duplicate layer, in menu COLOR -> LEVEL. 3. add alpha mask to original layer
4. copy duplicate layer into the alpha mask of the original. 5. delete duplicate layer.
6. If result is not ok then return to 1. As you can see this workflow is a headache, specially point 6 which is often achieved. Any thoughts

1. Create a channel mask from the grayscale value. 2. On the channel mask, use the threshold tool.

Voilà!

Mein öffentlicher Schlüssel / My public key: 4096R/600ACB3B 2012-04-01
Fingerabdruck / Fingerprint:
9902 575B B9A0 C339 CFDF  250B 9267 CA6B 600A CB3B
Runterladen z.B. bei/ Get it e.g. from:
pgp.mit.edu, subkeys.pgp.net, pgp.uni-mainz.de, pool.sks-keyservers.net, ...
Ofnuts
2013-07-22 20:45:15 UTC (over 11 years ago)

feature request: alpha level

On 07/22/2013 09:34 PM, Daniel Hornung wrote:

On Monday, 22. July 2013 08:38:00 Alex Vergara Gil wrote:

Hello GIMP developers:

I am working on a project where I need to set all pixels below a level as alpha channel, is there a quick way to achieve this? The level can be both set a priori or adjusted dinamically, the second way is prefered. Right now my workflow includes: 1. duplicate layer. 2. use color level in duplicate layer, in menu COLOR -> LEVEL. 3. add alpha mask to original layer
4. copy duplicate layer into the alpha mask of the original. 5. delete duplicate layer.
6. If result is not ok then return to 1. As you can see this workflow is a headache, specially point 6 which is often achieved. Any thoughts

1. Create a channel mask from the grayscale value. 2. On the channel mask, use the threshold tool.

Voil!

+1

For step 2) you can also uses Levels, Curves or even Brightness/Contrast, to keep some intermediate values of opacity and achieve a smoother result.

Alex Vergara Gil
2013-07-23 14:07:30 UTC (over 11 years ago)

feature request: alpha level

From: "Ofnuts"
Sent: Monday, July 22, 2013 3:45 PM

On 07/22/2013 09:34 PM, Daniel Hornung wrote:

On Monday, 22. July 2013 08:38:00 Alex Vergara Gil wrote:

Hello GIMP developers:

I am working on a project where I need to set all pixels below a level as
alpha channel, is there a quick way to achieve this? The level can be both
set a priori or adjusted dinamically, the second way is prefered. Right now
my workflow includes: 1. duplicate layer. 2. use color level in duplicate layer, in menu COLOR -> LEVEL. 3. add alpha mask to original layer
4. copy duplicate layer into the alpha mask of the original. 5. delete duplicate layer.
6. If result is not ok then return to 1. As you can see this workflow is a headache, specially point 6 which is often
achieved. Any thoughts

1. Create a channel mask from the grayscale value. 2. On the channel mask, use the threshold tool.

Voil!

+1

For step 2) you can also uses Levels, Curves or even Brightness/Contrast, to keep some intermediate values of opacity and achieve a smoother result. _______________________________________________

Great!
I dont know this could be done so easily. Thanks! I have adapted my workflow now.
1. Decompose original image in whatever you want RGB, LHS, LAB or even grayscale. Then pick some channel.
2. Copy the selected channel into an alpha mask of the original image. 3. Use level tool in the mask (threshold is not good because it creates sharp edges, but Curves and brightness/Contrast are good choices also).

With this workflow you can also set an alpha level on a specified channel!

Thank you all