Re: L*a*b* image manipulation (was: Change PCS of CLUT input profile)
Re: L*a*b* image manipulation (was: Change PCS of CLUT input profile)
- Subject: Re: L*a*b* image manipulation (was: Change PCS of CLUT input profile)
- From: Steve Upton <email@hidden>
- Date: Thu, 11 Oct 2007 12:35:24 -0700
At 11:11 AM +0200 10/11/07, Mark wrote:
>Hello Steve, list
>
>[snip]
>
>>yes but be careful with Lab. It's a reasonable exchange space but manipulations in it can expose its flaws. De-saturating blue, for instance will turn them purple if you simply move in polar coordinates.
>>
>
>Now you really got me, I was hoping LAB would be the perfect color space for saturation, tone mapping, sharpening,.... manipulations.
I had a feeling, that's why I brought it up.
> I was hoping that changing saturation in LAB was just a matter of applying a multiplication to a*b and that tone mapping could be easily done with L* without affecting color.
L* is pretty good actually, it's a/b that'll get you. If you want to do these kinds of manipulation then you should either look at Bruce Lindbloom's correction profiles that unwarp Lab to some extent OR go the more popular route and look into color appearance models such as CIECAM02. Ref: Mark Fairchild's "Color Appearance Models"
* Publisher: Wiley; 2 edition (February 4, 2005)
* Language: English
* ISBN-10: 0470012161
* ISBN-13: 978-0470012161
Amazon and others have it listed.
>Is LAB particularly bad or does it just have it's flaws (as probably every color space has). What is it good for?
for what you are looking for, think of it as bad.
HTH
Regards,
Steve
________________________________________________________________________
o Steve Upton CHROMiX www.chromix.com
o (hueman) 866.CHROMiX
________________________________________________________________________
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