[postgis-devel] Postgis Raster JPEG 2000 (openjpeg)

[Nathaniel Clay]

Hi all,


This is just some food for thought and discussion. I've take a cursory look
at JPEG 2000 openjpeg. I think it may hold promise for a possible future
format or co-format for Postgis Raster in database storage.

   - Supports both Loss less and Lossful Compression approaching the
   performance of ERDAS ( uncompressed Gtif 200M, openjpeg JP2  25M Lossfull
   and 80M Lossless, ERDAS JP2 15M)
      - I don't have a ERADAS encoder license, but this image was of the
      same original
      - Openjpeg lossfull compression in my opinion visually identical to
      the original with default settings
      - Supports N band imagery
   - Multi-Resolution Packing
   - eg more than one raster resolution with in the "code stream"
      - can be ordered by user specification, default smallest to largest
      - This would allow us to get rid of the overview tables or make them
      views.
      -
      http://ericportis.com/posts/2014/resolution-progressive-jpeg2000-performance/
      - Extensible header
      - SRID, IPX,IPY, etc
      - Area of interest specification
      - Allows you to specify a region with in the same raster to have a
      higher bitrate, etc
   - Error Detection and Correction
   - Openjpeg project seems to be alive last commit was a few days a go.
   - BSD License


Possible Concerns identified so far:

   - Writes require a recode of the entire tile, however the tile size is
   user specifiable
   - takes a long time to encode image, ~10 sec on my system with the test
   image ( 3067x3777 8bit 4bands)
      - I dont have anything to compare it to, so I dont know if this is a
      good or bad
      - I havent tested on small image size and other possible scenarios.
      - Memory Usage seemed high during decode and encode, ~2G, I believe
   this is due to the decoder and encoder preallocate memory for all of the
   "Pyramids" and bands at once. (but have not investigated thoroughly) (
   Image Res 3067x 3777  8bit  4 bands)
   - Its included decoder application has weird issues with tif, other
   formats are fine. ( Dont think it has anything to do with the openjpeg lib)
      - May be indective of other problems

If I were to start on this project it would be some time in the future and
I would most likely require help and lots of input, but I thought I it
would be a good idea to bring, it up as a discussion point.

Any thoughts,


Nathaniel Hunter Clay
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