Re: [Lcms-user] Question related to curve smoothing

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

Hello,
I answered that mail on 24/3, see the answer attached.

shaper + 3D LUT is not supported by this function.

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



-----Original Message-----
From: Pekka Paalanen <pek...@ha...> 
Sent: Tuesday, May 6, 2025 9:40 AM
To: lcm...@li...
Subject: Re: [Lcms-user] Question related to curve smoothing

On Mon, 24 Mar 2025 11:39:03 -0300
Leandro Ribeiro <lea...@ri...> wrote:

> Hello,
> 
> Based on [1], we've added the code to decompose a cmsHTRANSFORM into a 
> shaper (3x1D LUT) + 3D LUT on Weston [2].
> 
> We want to smooth the shaper with cmsSmoothToneCurve(), but we don't 
> know exactly how to choose the lambda parameter. In [1] we have: 
> "lambda is a parameter by which we can trade smoothness of z against 
> fit to data y". But would there be any drawback in using lambda == 0, 
> i.e. allowing "full smoothness"?
> 
> Any feedback from your experience with that would be appreciated.
> 
> [1] https://www.littlecms.com/ASICprelinerization_CGIV08.pdf
> [2] 
> https://gitlab.freedesktop.org/wayland/weston/-/merge_requests/1644
> 

Hi everyone,

we still don't know about this.

How do people choose the smoothing parameters for the shaper + 3D LUT case?


Thanks,
pq