Hi Marti,
Thank you for your quick response!
I must admit I had not looked at the L*-value in PhotoShop, and I think that
lcms 1 has a reasonable behaviour.
However, since the "color engine triad" apparently try to find the nearest
L*a*b*-color in this case I will try out lcms 2.0 when time permits.
We will give it a good whack - we have some guys around that are rather picky
about their colors.
I have been following your 2.0 blog for a while, but could I ask for a quick
comment about how mature you think it is?
Have a nice weekend,
Esben Høgh-Rasmussen Myosotis
Software Engineer
Phase One A/S
Roskildevej 39
DK-2000 Frederiksberg
Denmark
Phone: + 45 36 13 12 07
Fax.: + 45 36 46 02 22
Mobile: + 45 28 51 10 79
E-mail: e...@phaseone.com
www.phaseone.com <http://www.phaseone.com/>
________________________________
From: Marti.Maria [mailto:marti.ma...@littlecms.com]
Sent: 5. februar 2010 15:49
To: Esben Høgh-Rasmussen
Cc: lcms-user@lists.sourceforge.net
Subject: Re: [Lcms-user] Bad clipping by lcms
Hi
If you open the source image in photoshop and examine it with the color picker,
you will see all pixels do have L*=0
lcms 1.x assumes this is black, no matter the chroma.
lcms 2.0 does not make such assumption, it gives a result equal to the Adobe
and MS samples you sent.
The first beta will be available in a day or two.
Regards
Marti.
Esben Høgh-Rasmussen wrote:
Hello,
I have tried to use lcms for some conversions, but I stumbled over an
example where it appears to do a poor job.
It is an image from a digital camera and I want to convert it to sRGB
(or something) using a color profile (embedded):
ftp://updates.phaseone.com/prerelease/Images/lcms/In-16bit.tif
It is a rather dark and outside the profile gamut, but it renders well
using Microsoft, Adobes and Apples color management engines.
Here are conversions using Adobe, Microsoft and LCMS:
http://updates.phaseone.com/prerelease/Images/lcms/Out-16bit-sRGB-Adobe.tif
http://updates.phaseone.com/prerelease/Images/lcms/Out-16bit-sRGB-Microsoft.tif
http://updates.phaseone.com/prerelease/Images/lcms/Out-16bit-sRGB-LCMS.tif
Black-poiont compensation was turned off on the Adobe conversion
(performed by PhotoShop).
The Microsoft engine was performed using native calls.
This particular conversion was created with the flags
cmsFLAGS_HIGHRESPRECALC | cmsFLAGS_BLACKPOINTCOMPENSATION, but I tried just
about any permutation and the problem is basically the same regardless of
intent.
Just to check I am not completely insane I tried to do the conversion
in Gimp (based on LCMS).
First I converted to 8-bit in PhotoShop and then did the conversion in
both:
http://updates.phaseone.com/prerelease/Images/lcms/Out-8bit-sRGB-Adobe.tif
http://updates.phaseone.com/prerelease/Images/lcms/Out-8bit-sRGB-GIMP.tif
Same result, so I conclude that this is how LCMS handles the conversion.
Is there a way to solve this issue?
Kind regards,
Esben Høgh-Rasmussen Myosotis
Software Engineer
Phase One A/S
Roskildevej 39
DK-2000 Frederiksberg
Denmark
Phone: + 45 36 13 12 07
Fax.: + 45 36 46 02 22
Mobile: + 45 28 51 10 79
E-mail: e...@phaseone.com
www.phaseone.com <http://www.phaseone.com/>
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