Add support for jpeg2000 writing

[mraspaud]

• Tests added (for all bug fixes or enhancements)
• Tests passed (for all non-documentation changes)
• Passes git diff origin/master **/*py | flake8 --diff (remove if you did not edit any Python files)
• Fully documented (remove if this change should not be visible to users, e.g., if it is an internal clean-up, or if this is part of a larger project that will be documented later)

[coveralls]

Coverage increased (+0.08%) to 89.017% when pulling 55d7585 on mraspaud:feature-jp2000 into 8073e70 on pytroll:master.

[djhoese]

Looks good but I have a couple questions. If we are now saving JPEG2000 files (can PIL save these?) with rasterio then is it possible to save all of the image formats with rasterio? Should PIL only be used as a fall back? What does rasterio do with chunked saving? I didn't think JPEG2000 supported that?

[mraspaud]

Yes, rasterio can save in any format that gdal supports basically, so even png for example. As an extra feature, it does save a extra xml file on the side with geographical info for those formats that don't support having it inside the image file. So in principle, we could have PIL as a backup only.

Regarding chunked saving, you are right that rasterio doesn't support it for jpeg2000. The format seems to support it, but somewhere along the way it got lost, probably at the gdal driver stage. But the benefit of jpeg2000 is reduced file size, about 1/4 of the size for large SAR images I observed. And QGIS can read them.

[djhoese]

Does saving a chunked PNG image with rasterio produce a different file than using PIL? What about PngInfo or whatever that PIL uses? Does rasterio or gdal have an option for not creating the xml file?

[mraspaud]

I haven't tested rasterio for saving PNGs so much, so I really have no clue. As for skipping the xml creation, I've looked a bit, but couldn't find anything. So maybe PIL should be kept in satpy as it is for now.