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Threshold Alpha totally doesn't work in 2.10 but works fine in 2.08

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Threshold Alpha totally doesn't work in 2.10 but works fine in 2.08
jupiter Offline
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#1
Yesterday, 08:33 PM (This post was last modified: Yesterday, 08:34 PM by jupiter.)
I just spent a whole day trying a dozen different methods that are supposed to make all the transparent *colored* pixels in an image completely opaque while keeping the completely transparent pixels as they are. However in 2.10 whenever I set Threshold Alpha to zero as often suggested it has no effect and GIMP simply resets it to 0.5. Then I tried this in 2.08 and it worked fine right away.

Does that mean it's just plain broken in 2.10? Or is there an obscure deeply buried setting that somehow got changed in 2.10 that I'm not aware of and is blocking changes to the threshold? The Alpha channel is definitely not locked.
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Ofnuts Offline
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#2
Yesterday, 09:09 PM
(Yesterday, 08:33 PM)jupiter Wrote: I just spent a whole day trying a dozen different methods that are supposed to make all the transparent *colored* pixels in an image completely opaque while keeping the completely transparent pixels as they are. However in 2.10 whenever I set Threshold Alpha to zero as often suggested it has no effect and GIMP simply resets it to 0.5. Then I tried this in 2.08 and it worked fine right away.

Does that mean it's just plain broken in 2.10? Or is there an obscure deeply buried setting that somehow got changed in 2.10 that I'm not aware of and is blocking changes to the threshold? The Alpha channel is definitely not locked.

Layer > Transparency > Threshold alpha works for me. Using a  layer mask (initialized with Transfer layer's alpha channel) and thresholding the mask also works.

Is the image color-indexed? In such images layer opacity follows non-obvious rules.
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jupiter Offline
Junior Gimper
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#3
Yesterday, 09:29 PM
(Yesterday, 09:09 PM)Ofnuts Wrote: Using a  layer mask (initialized with Transfer layer's alpha channel) and thresholding the mask also works.

Tried that, didn't work.
(Yesterday, 09:09 PM)Ofnuts Wrote: Is the image color-indexed? In such images layer opacity follows non-obvious rules.

It's not color-indexed. There has to be some other property of the image or setting in GIMP that blocks or breaks Threshold Alpha settings. If not it has to be a bug.
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Ofnuts Offline
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#4
Today, 01:03 AM
(Yesterday, 09:29 PM)jupiter Wrote:
(Yesterday, 09:09 PM)Ofnuts Wrote: Using a  layer mask (initialized with Transfer layer's alpha channel) and thresholding the mask also works.

Tried that, didn't work.
(Yesterday, 09:09 PM)Ofnuts Wrote: Is the image color-indexed? In such images layer opacity follows non-obvious rules.

It's not color-indexed. There has to be some other property of the image or setting in GIMP that blocks or breaks Threshold Alpha settings. If not it has to be a bug.

Can you share an example XCF image (see attachments link at top right), possibly cropped to a small size to fit the 2MB XCF limit?
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