[Lcms-user] Using CreateTransform in LCMS1 and LCMS2

[Lee B. <le...@bo...>]

Hi,

I'm in the process of updating an application that uses LCMS to do colour transformation to LCMS2 and have a problem.

Converting a CMYK value to Lab gives quite different values using the same profile and (as far as I can tell) the same settings.

LCMS2 transform function is this:

  return LCMS2TransformMBS.CreateTransform(p,LCMS2MBS.kTYPE_CMYK_16,lcms2labprofile,LCMS2MBS.kTYPE_Lab_16,3)
  
LCMS1 Transform function is this:
  
return LCMSMBS.CreateTransform(p,LCMSMBS.TYPE_CMYK_16,lcmslabprofile,LCMSMBS.TYPE_Lab_16,3)
 
where p is an opened  CMYK ICC profile, lcmslabprofile and lcms2labprofile is a simple CreateLab4Profile with no arguments.

Using these transforms with a CMYK value of 0,0,0,0 (or any CMYK value) gives different Lab Values -  up to about 1.5dEab.

Viewing the memoryblock I get back when calling the transform shows the values are different too.

LCMS1 values match very well those I get when using the Apple ColorSync utility.

Hope someone can help

Regards,

Lee Badham

www.bodoni.co.uk | www.presssign.com