Sign up now! · Forgot password?
RSS/Atom feed identi.ca Twitter

bug when trying to edit color channels of a transparent image

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.

2 of 2 messages available
Toggle history

Please log in to manage your subscriptions.

bug when trying to edit color channels of a transparent image Tcll 27 Jan 21:41
  bug when trying to edit color channels of a transparent image Ofnuts 28 Jan 21:26
Tcll
2018-01-27 21:41:59 UTC (9 months ago)

bug when trying to edit color channels of a transparent image

the issue here is when opening a transparent image, the color channels don't show the full color info, see here: https://cdn.discordapp.com/attachments/98580359909773312/406830380180570113/unknown.png

here's the very same PNG opened in MS Paint: (expected when hiding the alpha channel)
https://cdn.discordapp.com/attachments/98580359909773312/406830457083133952/Pikachu_eyesYellow.00c.png

if everything was correct, the color channels would display the yellow and red around the eye.
just because the image is transparent doesn't mean the colors don't affect the model it's applied to.

but what's even more of an issue is I'm trying to edit out the red circle as I want what's hidden to be fully yellow, but the only way I can seem to achieve that is to pull the alpha channel from the image and make the image fully opaque before editing the colors as hiding the alpha channel makes the entire image transparent.

getting the alpha channel seems to be anything but easy as well as hiding the RGB channels makes the entire image black, rather than just displaying the alpha mask between black and white.

so yeah... few bugs there actually... hopefully things can be improved/fixed soon :)

Ofnuts
2018-01-28 21:26:32 UTC (9 months ago)

bug when trying to edit color channels of a transparent image

On 01/27/18 22:41, Tcll wrote:

the issue here is when opening a transparent image, the color channels don't show the full color info, see here: https://cdn.discordapp.com/attachments/98580359909773312/406830380180570113/unknown.png

The RGBA channels at the top are not the channels of a specific layer, but the channels of the final composite image. So while the behavior may not be what you expect it could still be correct.

here's the very same PNG opened in MS Paint: (expected when hiding the alpha channel)
https://cdn.discordapp.com/attachments/98580359909773312/406830457083133952/Pikachu_eyesYellow.00c.png

if everything was correct, the color channels would display the yellow and red around the eye.
just because the image is transparent doesn't mean the colors don't affect the model it's applied to.

but what's even more of an issue is I'm trying to edit out the red circle as I want what's hidden to be fully yellow, but the only way I can seem to achieve that is to pull the alpha channel from the image and make the image fully opaque before editing the colors as hiding the alpha channel makes the entire image transparent.

getting the alpha channel seems to be anything but easy as well as hiding the RGB channels makes the entire image black, rather than just displaying the alpha mask between black and white.

The canonical way of editing the alpha channel of a layer is to use a layer mask. Here is a good tutorial on the subject:

https://patdavid.net/2011/10/getting-around-in-gimp-layer-masks.html