Trouble using JP2
Posted: 2008-06-01T22:55:18-07:00
I want to archive some "original" scan files with minimum loss but some compression, so I'm converting the 48-bit color TIFF files to JPEG-2000.
First, the documentation is wrong: the default produces much larger files than the -quality 85 option. I don't know if it is defaulting to lossless or virtually lossless, but it doesn't compress much either.
Second, it does not copy the ICC/ICM profile from the original, but marks it as sRGB incorrectly.
Profiles:
Profile-icc: 3024 bytes
IEC 61966-2.1 Default RGB colour space - sRGB
the data is not transformed; the values are still as in the original file (Adobe RGB).
If I then use morgrify -profile to attach AdobeRGB.icc (as extracted from the original file using convert), it turns a 8 meg file into a 35 meg file! Clearly it also re-encoded it at a higher bit rate, which is a stupid thing to do by default because it was already "lost". Furthermore, it didn't include the profile! Identify -verbose shows it still has the wrong sRGB profile.
What's going on here? How do I use this correctly for JP2 files? I'm also interested in other options for color sampling etc. but I want to get the basics to work first.
--John
First, the documentation is wrong: the default produces much larger files than the -quality 85 option. I don't know if it is defaulting to lossless or virtually lossless, but it doesn't compress much either.
Second, it does not copy the ICC/ICM profile from the original, but marks it as sRGB incorrectly.
Profiles:
Profile-icc: 3024 bytes
IEC 61966-2.1 Default RGB colour space - sRGB
the data is not transformed; the values are still as in the original file (Adobe RGB).
If I then use morgrify -profile to attach AdobeRGB.icc (as extracted from the original file using convert), it turns a 8 meg file into a 35 meg file! Clearly it also re-encoded it at a higher bit rate, which is a stupid thing to do by default because it was already "lost". Furthermore, it didn't include the profile! Identify -verbose shows it still has the wrong sRGB profile.
What's going on here? How do I use this correctly for JP2 files? I'm also interested in other options for color sampling etc. but I want to get the basics to work first.
--John