Re: [Lcms-user] Profile/conversion problem

[<ma...@li...>]

Hi,

> > I'm not able to get similar values by doing it in LCMS. The olny profile I
> > can use is Tiflab8space.icm. If I don't specify the profile and it uses the

Thanks for the images.

Sigh. :-( Ok. It happens that Photoshop does _not_ follow the TIFF 6.0 spec
and stores Lab using D50 instead of D65. As a result, Lab images saved in
Photoshop does behave quite different, specially on blues.

This "bug" pops up quite frequently, so, since it seems Photoshop is doing the
"true" standard instead of the spec, I have put a profile for this case in the site:

http://www.littlecms.com/tiff8adobe.zip

In the zip  is also the code to generate the profile, if anyone is interested on how
to generate weird profiles using lcms. This profile is smaller that the anterior
Tifflab8spac.icm and not subjected to any Linotype copyright anymore.
I will check it carefully this week, but for now seems to work quite well on your
test images.

The CMYK bitmap does give pretty same values that Photoshop. One important
thing: your Lab TIFF does have a embedded profile. This is wrong because Lab
does not need any profiles and worst, the profile is operating in RGB, and tagged
as Lab. If you are using TIFFICC to do checking, assure to use -n to ignore
embedded profile.


Best Regards,
Martí Maria
The little cms project
http://www.littlecms.com
ma...@li...


----- Original Message -----
From: "Martí Maria" <ma...@li...>
To: "Gunnar Lieb" <ki...@f1...>; <Lcm...@li...>
Sent: Monday, January 21, 2002 9:41 AM
Subject: Re: [Lcms-user] Profile/conversion problem


> Hi,
>
> > I'm trying to reproduce a color conversion from LAB->CMYK. The original
> > conversion is made by Heidelberg Linocolor.
> >
> > I'm not able to get similar values by doing it in LCMS. The olny profile I
> > can use is Tiflab8space.icm. If I don't specify the profile and it uses the
>
> Are you decoding a TIFF file?. Tiflab8space.icm is only valid on 8-bit TIFF.
> This profile does hold Lab AND a special decoding  for 8 bit TIFF.
> If your Lab source is any other, INCLUDING 16 BIT TIFF, try
> lcmslabi.icm. Programatically, you can use the new built-in Lab profile:
>
> cmsCreateLabProfile(NULL)
>
> That  is present on ver 1.08. I would recommend this latter, since it
> takes 0 bytes on disk. If you are using tifficc, lcmslabi.icm will do the
> job. I have done a lot of testing on Lab->CMYK and works quite well.
>
> About the embedded profile... if the file is storing data on Lab space, there
> is no need of embedded profile, data is already device independent.
>
> Regards,
> Martí Maria
> The little cms project
> http://www.littlecms.com
> ma...@li...
>
>
> ----- Original Message -----
> From: "Gunnar Lieb" <ki...@f1...>
> To: <Lcm...@li...>
> Sent: Sunday, January 20, 2002 2:13 PM
> Subject: [Lcms-user] Profile/conversion problem
>
>
> > Hi,
> >
> > I'm trying to reproduce a color conversion from LAB->CMYK. The original
> > conversion is made by Heidelberg Linocolor.
> >
> > I'm not able to get similar values by doing it in LCMS. The olny profile I
> > can use is Tiflab8space.icm. If I don't specify the profile and it uses the
> > embeded I get strange colors. It looks like solarized!. If I use the
> > mentioned LAB profile there a big differences in the color. I.e. I get in
> > - Linocolor conversion a blue with c96 m72 y0 k0
> > - LCMS conversion with c95 m66 y13 k5
> >
> > I tried the t option with all values, but the conversion remained different.
> >
> > So with does the embedded profile produces such a strange color?
> > Are there any other options to look for?
> >
> > Thanks,
> >
> > Gunnar
> >
> >
> > _______________________________________________
> > Lcms-user mailing list
> > Lcm...@li...
> > https://lists.sourceforge.net/lists/listinfo/lcms-user
> >
> >
>