[gdal-dev] lossless jpeg crop in gdal?

[Matt.Wilkie at yukon.ca]

I recently learned that jpegtran from the JPEG library has the ability to crop and save a new jpeg losslessly:

These transformations are each completely lossless and reversible. The transformations on the image data comprise:
·         eliminate non-standard application-specific data inserted by some image programs,
·         perform certain transformations on a file, such as:
o    discarding of colour channels (conversion to greyscale),
o    rotating and flipping in steps of 90 degrees,
o    cropping at image block borders (every 8×8 or 16×16 pixels),
o    rescaling.[7]<https://en.wikipedia.org/wiki/Libjpeg#cite_note-jpegtran-7>
These are lossless and reversible only regarding the image data that is kept. Reencoding with repeated lossy quantisation of the image data (generation loss) does not take place.

-- https://en.wikipedia.org/wiki/Libjpeg#jpegtran


Can GDAL take advantage of this for jpeg-in-geotiff images?

Matt Wilkie
Geomatics Analyst
Environment | Technology, Innovation and Mapping
T 867-667-8133 | Yukon.ca<http://yukon.ca/>
Hours: 08:30-16:30, Tue-Wed: Office, Thu-Fri: Remote.
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