LibTiff Mailing List
TIFF and LibTiff Mailing List Archive
December 2009
Previous Thread
Next Thread
Previous by Thread
Next by Thread
Previous by Date
Next by Date
Contact
The TIFF Mailing List Homepage
This list is run by Frank Warmerdam
Archive maintained by AWare Systems
Thread
2009.12.28 17:51 "Re: bug in tiff2pdf, when handling Lab images", by Manlio Perillo
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Lee Howard ha scritto: > Manlio Perillo wrote: > [...] >> The problem is with tiff2pdf writing two times the WhitePoint entry in >> the Lab dictionary: >> >> /ColorSpace [/Lab << >> /WhitePoint [0.9643 1.0000 0.8251] >> [0.9643 1.0000 0.8251] >> /Range [-127 127 -127 127] >> >>>> ] > > If you look at the code this appears to be intentional: > Ok, maybe I have found the real cause of the problem. The TIFF 6.0 specification states that, for L*a*b* color space (PhotometricInterpretation): ... WhitePoint: does not apply ... The reference white for this data type is the perfect reflecting diffuser (100% diffuse reflectance at all visible wavelengths). The L* range is from 0 (perfect absorbing black) to 100 (perfect reflecting diffuse white). The a* and b* ranges will be represented as signed 8 bit values having the range -127 to +127. ... Generally, D65 illumination is used and a perfect reflecting diffuser is used for the reference white. D65 is also the default value of the WhitePoint field. The Adobe Photoshop TIFF Technical Notes, instead, states: WhitePoint: default is CIE D50, may be omitted if default value So in tiff2pdf code both cases are considered; IMHO one of the cases should have been commented but the author forgot to do so. The Photoshop technical notes are the one to follow, since the original TIFF 6.0 specification is wrong. Regards Manlio -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iEYEARECAAYFAks48A8ACgkQscQJ24LbaUQHKQCfbrEKJaeivcHeZSqSbwfmhZha 68MAnjbYmqmRQfW64WEQhLgEM9TztJVO =o92k -----END PGP SIGNATURE-----