JP2 derivative 10x larger than OBJ

[Brandon Weigel]

Strange behaviour with a smallish TIFF... I've got a book whose pages are quite slow to load. Turns out that while the individual page TIFFs are around 189 KB, the JP2 derivatives are much larger -- 1.33 MB -- instead of smaller. (https://athabascau.arcabc.ca/islandora/object/au%3A9494) Is there a way to make this, well, not happen? Aren't the JP2s intended to be smaller than the OBJs?

[Tristan Chambers]

Hi Brandon,

It looks to me like your OBJ is a bitonal TIFF. Bitonal TIFFs are actually very efficient at storing printed text, when they employ a lossless compression like LZW. Whereas JPEG (and JPEG2000) have a minimum bit depth of 8 bits in greyscale mode and are terribly inefficient at storing printed materials. Unfortunately there is an inherent incompatibility with using JP2 for this purpose, which comes down to the fact that JPG was designed for photographic images with lots of tonal gradations. For a more in-depth discussion of this check out this stackexchange thread:

https://photo.stackexchange.com/questions/40263/is-it-possible-to-make-a-1-bit-bitonal-jpeg

I did a little research on this in the past and discovered that JPG 2000 Part 6 does seem to contain provisions for bitonal content:

https://www.loc.gov/preservation/digital/formats/fdd/fdd000144.shtml

However my sense is that Islandora hasn't implemented this extension. Nor is it clear to me whether this has ever been implemented by anyone? This would have to be tested at all levels: JP2 creation (kakadu or imagemagick) image server (djatoka or cantaloupe) and viewer (open sea dragon). I'd be curious to hear if there are other Islandora folks who might have any insider info on priorities about this. Is there even a ticket about it?

Best regards,

Tristan

On Fri, Nov 30, 2018 at 2:14 PM Brandon Weigel <jeanpau...@gmail.com> wrote:

Strange behaviour with a smallish TIFF... I've got a book whose pages are quite slow to load. Turns out that while the individual page TIFFs are around 189 KB, the JP2 derivatives are much larger -- 1.33 MB -- instead of smaller. (https://athabascau.arcabc.ca/islandora/object/au%3A9494) Is there a way to make this, well, not happen? Aren't the JP2s intended to be smaller than the OBJs?

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Digital Library Applications Administrator
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[Brandon Weigel]

Thanks for that information, Tristan. That definitely helps me to understand the problem.

How plausible is it to create JP2 part 6 derivatives locally, if it can't be done in Islandora? I'm struggling somewhat to find a way to do it.

[tcha...@smith.edu]

Brandon,

I haven't had a chance to try it myself. I'd love to hear what you learn if you give it a shot.

Thanks,

Tristan