Re: [Lcms-user] Unexpected gray to RGB result

[<mar...@li...>]

Hi,

The embedded profile is wrong. It claims to be V4 and perceptual, but fails to scale on perceptual black. 

See https://color.org/specification/ICC.1-2022-05.pdf

"6.3.4.3 PCS encodings for white and black"
"Perceptual transforms developed to meet ICC specifications prior to version 4.0 frequently use zero to represent 
the black point, and thus do not conform to this specification."

Other CMM may choose to reject the profile, lcms uses it, despite it is wrong.

Regards
Marti Maria
The LittleCMS Project
https://www.littlecms.com

-----Original Message-----
From: Ralf Junker <ral...@gm...> 
Sent: Saturday, November 26, 2022 11:13 PM
To: lcm...@li...
Subject: [Lcms-user] Unexpected gray to RGB result

I try to use lcms2 to convert gray to RGB, but the output differs considerably.

So I double-checked with

   jpgicc gray-inverted-profile-linear.jpg gray-rgb-linear.jpg

but the result is the same: Unexpected saturation of dark gray areas to pitch black.

As reference of the expected outcome, please take a look at gray-chromium.png to see how Chromium renders gray-inverted-profile-linear.jpg. Firefox and GIMP look just the same.

Am I missing something? I am grateful for any advice!

Ralf

PS I hope the list accepts attachments. If not please advice how to send the images in question.