[Solved] How to embed an sRGB profile with g=1.0 after GC conversion

Having tech problems? Post them here and do not worry, there is always a solution for you.
User avatar
forum_adm
Site Admin
Posts: 1814
Joined: Fri Dec 23, 2016 9:41 am
Location: Germany
Country: Germany
Contact:

Re: How to embed an sRGB profile with g=1.0 after GC conversion

Post by forum_adm »

I don't understand the problem.

Any gamma change within GraphicConverter is directly applied to the image pixel data. The color profile stays the same.

The gamma value inside PNGs is legacy and should no longer used. Color management should always be done by a color profile.

What is your exact workflow?
es
Posts: 114
Joined: Sun Dec 04, 2022 6:24 pm

Re: How to embed an sRGB profile with g=1.0 after GC conversion

Post by es »

Ok, let's try this simple example, maybe it will clear things up:

Create two new files with GC with the following settings
  1. 1st file: 16b with the built-in sRGB profile
    1'sRGB built-in'.png
    1'sRGB built-in'.png (50.01 KiB) Viewed 845 times
  2. 2nd file: 16b with the a 'sRGB Gamma=1.0' profile
    2'sRGB Gamma=1.0'.png
    2'sRGB Gamma=1.0'.png (50.99 KiB) Viewed 845 times
  3. Now in each file add Core Image Filters → Linear Gradient from pure green to pure red.
    They look the same!
  4. Save these files (due to 3 image forum limit will post them in the following message) and reopen them
    Now the look different!
The second file is darker because it's reopened with the default sRGB profile, not with the linear light profile! So the information that it was created with g=1.0 is lost
es
Posts: 114
Joined: Sun Dec 04, 2022 6:24 pm

Re: How to embed an sRGB profile with g=1.0 after GC conversion

Post by es »

The two files with linear gradients added
1st file
1 48bpc sRGB built-in, Linear gradient G→R.png
1 48bpc sRGB built-in, Linear gradient G→R.png (7.43 KiB) Viewed 845 times
2nd file
2 48bpc 'sRGB, Gamma=1.0', Linear gradient G→R.png
2 48bpc 'sRGB, Gamma=1.0', Linear gradient G→R.png (7.24 KiB) Viewed 845 times

So do you think that when saving the second file created with a "non-sRGB" profile GC should've embedded it to preserve the difference in gamma value while still not embedding the proper sRGB profile (not to waste space)?
User avatar
forum_adm
Site Admin
Posts: 1814
Joined: Fri Dec 23, 2016 9:41 am
Location: Germany
Country: Germany
Contact:

Re: How to embed an sRGB profile with g=1.0 after GC conversion

Post by forum_adm »

Ah - now it is clear.
Can you please forward the gamma=1 profile to support@lemkesoft.de ?
es
Posts: 114
Joined: Sun Dec 04, 2022 6:24 pm

Re: How to embed an sRGB profile with g=1.0 after GC conversion

Post by es »

Sure thing, see the attached zip, it was in "~/Library/Application Support/GraphicConverter/Profiles", but then I guess your app just saves various profiles it encounters there (I initially thought that it was one of your default profiles added on install)
Attachments
sRGB, Gamma=1.00.icc.zip
(388 Bytes) Downloaded 73 times
User avatar
forum_adm
Site Admin
Posts: 1814
Joined: Fri Dec 23, 2016 9:41 am
Location: Germany
Country: Germany
Contact:

Re: How to embed an sRGB profile with g=1.0 after GC conversion

Post by forum_adm »

Please recheck with build 5699. It checks now the estimated gamma value if sRGB is detected.
Post Reply