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

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

Hi,

Thanks for checking.

> One more question, if I may: You wrote that the fix is in the "algorithm
to detect those bad profiles". What corrections would be needed to generate
a good profile in the first place?

ICC spec expects a "good" V4 perceptual profile to return "perceptual black"
on darkest colorant (gray=0). This is around Lab=(3.14, 0, 0) or XYZ=(
0.3357, 0.3479, 0.2869). 
You profile was trying to trick the CMM by returning Lab=(100, 0, 0) on the
darkest colorant. And made it crazy. Now it detects this and let you to take
full control.

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

-----Original Message-----
From: Ralf Junker <ral...@gm...> 
Sent: Tuesday, November 29, 2022 10:35 AM
To: lcm...@li...
Subject: Re: [Lcms-user] Unexpected gray to RGB result

On 27.11.2022 17:44, mar...@li... wrote:

> Now it is fixed by
> https://github.com/mm2/Little-CMS/commit/caab4c07e60022a0f776b543eaa30
> 785e2bb42ed

Thanks for the fix. I confirm it works well. lcms2 now generates visually
identically image to Chromium, Firefox, and Gimp.

One more question, if I may: You wrote that the fix is in the "algorithm to
detect those bad profiles". What corrections would be needed to generate a
good profile in the first place?

Ralf


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