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How to install gimp-avif-plugin ?
#1
Hi. Could please anyone explain - how to intall this plugin (https://github.com/novomesk/gimp-avif-plugin) to gimp?
As far as I understood it is for linux (sorry, I am just a ordinary windows 10-user). And there is no instruction on how to make it work for windows?
P.s. I would like to try this plugin as with inbuild gimp settings, but even with lossless encoding image change some color in some details on the picture.
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#2
(01-25-2023, 05:09 PM)Sunweb Wrote: Hi. Could please anyone explain - how to intall this plugin (https://github.com/novomesk/gimp-avif-plugin) to gimp?
As far as I understood it is for linux (sorry, I am just a ordinary windows 10-user). And there is no instruction on how to make it work for windows?
P.s. I would like to try this plugin as with inbuild gimp settings, but even with lossless encoding image change some color in some details on the picture.

It does say it is only for Gimp 2.99 It comes already installed in the Windows version. You can run both Gimp 2.10 and Gimp 2.99 separately. Gimp 2.10.32 will open a .avif exported from Gimp 2.99

This in a Win 10 (VM) Gimp 2.99.12 (needs an update) Maybe not all the options that you require, but more than Gimp 2.10

   

You can download a Windows installer for Gimp 2.99.14 from here: https://download.gimp.org/gimp/v2.99/windows/

I have to confess, I do not understand your PS.
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#3
Thank you!
I have tried development version. Unfortunately different setting doesn't solve an issue with color change anfer encoding in avif (and perhaps even add another one if I tried to check image via avif validator) but this gave me something for further investigation.
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#4
(01-25-2023, 05:49 PM)rich2005 Wrote: I have to confess, I do not understand your PS.

Sorry, not native speaker for English, but I will try explain what I noticed:

I tried to convert a regular .png screenshot to .avif image via GIMP.
But no matter what settings I use - some details of the image are differ from the original .png. And i can't understand "why?".
For example: download please these 3 images.
The archive contains 3 files:
1) File "Example" shows an element which you could take a look.
2) File "PNG" is an original screenshot itself in .png
3) File "AVIF GIMP 2-10 lossless" is an .avif image created by GIMP 2.10.32. It was created with "lossless" settings.

If you compare the element that I marked from the file 1, on the files 2 and 3 you could notice a difference in a color (after GIMP it looks like a more blue color). In GIMP 2.99.14 as far as check result is same.

Example

Upd.

I did also the same conversion via paint.net and the colors matched there. But .avif image after paint.net don't want to open in Firefox.
Image after GIMP 2.10.32 works in Firefox as it supposed, but after conversion I noticed this color change, so this is what this question was about - why does image (even lossless) change it's color in details like this.
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#5
If this is only to convert images, have you tried ImageMagick. As simple as

Code:
convert PNG.png Example.avif

If I do the conversion both ways (PNG > Avif > PNG) and compare the two PNG (histogram of the difference between the two images), they are strictly identical.

Note that AVIF is a very new format, support can be buggy, and the bug can be anywhere in your toolchain, the conversion, or the browsing.
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#6
@Sunweb
A new day, some more tests.

1. I can not visually see any difference between your PNG .png and your AVIF GIMP 2-10 lossless.avif Using Sample points on your area of interest, there are tiny changes in blue and red but literally just 1 point example  50 -> 51.

2. The whole point is a smaller file size and setting lossless might be unjustified. see:  https://www.finally.agency/blog/what-is-...age-format I do not know how reliable that is, it is about 18 months old and it claims avif lossless implementation is not very good.
for file size and I see no visible change in colours unless you are very picky.

3. Using ImageMagick (IM), You need a IM7, current is 7.1 some info here: https://avif.io/blog/tutorials/imagemagick/

Depending on settings I can get a 100% quality with a file size = 939 kb down to 80 quality = 28.7 kb Zoom in to pixel size, you can see differences, the avif has implemented some smoothing, but that is the trade-off for file size and I see no visible change in colours unless you are very picky.

Code:
magick -quality 80 -define heic:speed=2 PNG.png png2.avif

Attached as an IM example. Unzip it.

Paint.Net files not compatible with browser ? I do not use, but check you have the correct files installed. https://avif.io/blog/tutorials/paintnet/

--------------------
Edit: avif is not a format I use, but it is basically a video format. ffmpeg is another utility. A little like ImageMagick (IM), if you have an up-to-date version, it will convert png -> avif.  It might be closer to that Gimp 2.99 plugin for YUV colorspace, I have not got that far yet.

However, for IM7 you can get a higher bit depth which might be closer to your png and a much smaller filesize.

Code:
magick PNG.png -quality 80 -depth 12 80-12.avif

That opens in Gimp as 16 bit file. Open As Layers the PNG.png and compare.

attached 80-12.avif zipped, unzip it.

One thing I noticed in the png, some artifacts Was it originally a jpeg ?


Attached Files
.zip   png2.avif.zip (Size: 28.16 KB / Downloads: 13)
.zip   80-12.avif.zip (Size: 123.28 KB / Downloads: 13)
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#7
(01-26-2023, 10:11 AM)rich2005 Wrote: One thing I noticed in the png, some artifacts Was it originally a jpeg ?

No, this screeschoot was made with windows 10 inbuild screeschooter due the game. And as far as I know, it can save only .png files.

Thank you guys (Ofnuts and rich2005)!
That were exactly what I need to hear and read!
Issue is solved.
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#8
The issue was in "Windows Photo Viewer" itself.

Explanation
I tried to convert another screenshot and noticed that in .avif version it is slightly (but noticeably) brighter than version in .png
So I just googled something like "avif decoder make image brighter" and the first result (https://github.com/link-u/cavif/issues/40) described the same issue, but with different software. Andit was bingo!
I opened in the GIMP the second image that I encoded and there was NO difference in brightness.
I opened in the GIMP the first image (with the space-ship) that I encoded and there were NO noticeable difference in elements' colors.

My noob's verdict - please, do not compare two photos in "Windows Photo Viewer")
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