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HSV decompose
http://gimpchat.com/viewtopic.php?f=8&t=18351		 Page 1 of 1
Author:  dinasset [ Sat May 16, 2020 11:14 pm ]
Post subject:  HSV decompose
GIMP Version: 2.10.18
Operating System: Windows
GIMP Experience: Intermediate Level

List any relevant plug-ins or scripts:
(my Gimp comes from Samj's package)
decompose HSV
recompose


This is to inform interested gimpers that it seems (but it could be I do not understand properly the function) that applying:
- decompose HSV
followed by
-recompose
the result is very strange

Here the original:
Attachment:
fiore-rosa-2_ORIGINAL.jpg
fiore-rosa-2_ORIGINAL.jpg [ 132.24 KiB | Viewed 2592 times ]

Here after decompose HSV then recompose
Attachment:
fiore-rosa-2_after-decomposeHSV-recompose.jpg
fiore-rosa-2_after-decomposeHSV-recompose.jpg [ 176.95 KiB | Viewed 2592 times ]
Author:  Wallace [ Sat May 16, 2020 11:27 pm ]
Post subject:  Re: HSV decompose
Have you tried it on different images and sizes of images?
Author:  dinasset [ Sat May 16, 2020 11:56 pm ]
Post subject:  Re: HSV decompose
Good idea, Wallace.
Tried on another flower image and it works properly.
What could be the problem in the source image?
Coul you try on my first image to see whether it happens also in your PC/Gimp environment?
Author:  dinasset [ Sun May 17, 2020 12:00 am ]
Post subject:  Re: HSV decompose
Additional info:
using my first image (the one which has a wrong behaviour in HSV), when choosing either decompoce RGB or decompose HSL, the recompose works fine.
Author:  ofnuts [ Sun May 17, 2020 3:43 am ]
Post subject:  Re: HSV decompose
Same on my 2.10.14 et 2.10.19 freshly compiled from the official GIT source. Doesn't happen if the image is converted to 32-bit FP.
Author:  dinasset [ Sun May 17, 2020 5:21 am ]
Post subject:  Re: HSV decompose
Thanks Ofnuts. I'm not alone.
Author:  ofnuts [ Sun May 17, 2020 6:28 am ]
Post subject:  Re: HSV decompose
Issue submitted: https://gitlab.gnome.org/GNOME/gimp/-/issues/5097

Seems to be a problem with hue values=255.
Author:  rich2005 [ Sun May 17, 2020 6:31 am ]
Post subject:  Re: HSV decompose
Comparisons:

Works as expected in kubuntu 18.04 and regular (as-in from PPA) Gimp 2.10.14 and latest (14 may) Gimp 2.10.19 appimage.

Gives the fault in kubuntu (VM) 20.04 regular Gimp 2.10.18 (as-in from repo), a 2.10.18 snap version and exactly the same (14 May) 2.10.19 appimage as before.

not even going to hazard a guess ;)
Author:  ofnuts [ Sun May 17, 2020 6:56 am ]
Post subject:  Re: HSV decompose
rich2005 wrote:
Comparisons:

Works as expected in kubuntu 18.04 and regular (as-in from PPA) Gimp 2.10.14 and latest (14 may) Gimp 2.10.19 appimage.

Gives the fault in kubuntu (VM) 20.04 regular Gimp 2.10.18 (as-in from repo), a 2.10.18 snap version and exactly the same (14 May) 2.10.19 appimage as before.

not even going to hazard a guess ;)


Weird. I see the problem on my 2.10.14, I saw it in a self-compiled 2.10.18, and still see it in the self-compiled 2.10.19 with all latest updated. Are you using the same settings all over? If the image is converted to 32-bit FP the problem disappears.
Author:  rich2005 [ Sun May 17, 2020 7:58 am ]
Post subject:  Re: HSV decompose
Default settings for everything.

Again in kubuntu 20.04 and Gimp 2.10.18 That 32 bit FP works but so does 8 bit linear rather than 8 bit sRGB.

The devs have been fixing the broken CMYK decompose might be a consequence of that. Is it the libbabl package to blame? in 18.04 / 20.04 the packages are 1.72 / 1.74
Author:  ofnuts [ Mon May 18, 2020 5:20 am ]
Post subject:  Re: HSV decompose
Fixed: https://gitlab.gnome.org/GNOME/babl/-/issues/54

However, better be in high-precision mode for this kind of thing, Decompose/Recompose doesn't recreate the very same image, some RGB values get shifted a bit in the process.
Author:  dinasset [ Mon May 18, 2020 6:57 am ]
Post subject:  Re: HSV decompose
Thanks a lot !
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