Write output with UInt16 encoding

Currently the output is written as float. To save disk space, it could be interesting to save the output as Uint16 with a specific formula to retrieve the real value.

added Enhancements label

changed milestone to %1.1

Other ideas to investigate:

• Store the data in Float16 (keep only 4 digits for numbers)

• Remove LSB in float32 and use DEFLATE compression:

Geotiff Documentation

DISCARD_LSB=nbits ou nbits_band1,nbits_band2,...nbits_bandN : (GDAL >= 2.0) Définie le nombre de bites le moins significant à nettoyer, potentiellement dans différentes bandes. Le plan de compression sans perte est utilisé au mieux avec PREDICTOR=2 et LZW/DEFLATE.

The idea to remove the LSB bits seems nice.

Proposition: compression option: nothing / LSB+deflate / uint16 / uint32

If the need to uint is not confirmed, I propose to keep float type only. Usually, there is always a post-processing (filtering, detection, ...) which needs float value.

Proposition: compression option: nothing / deflate / remove_LSB8+deflate / remove_LSB16+deflate /

with deflate as default

• add compression lerc (requires GDAL 3.3)

created branch 66-write-output-with-uint16-encoding to address this issue

mentioned in merge request !101 (merged)

assigned to @lhermitte

In order to support any encoding wishes from the end-user (compression, tiling, interleaving...), I went with a first implementation supporting all the range of OTB extended filename.

However, this opens the doors to options that aren't really desirable from S1TIling perspective IMO (&writegeom, &writerpctags, &streaming, &box, &bands, &nodata, &epsg, &multiwrite).

Instead, I think we should restrict to GDAL creation options, and we also need to be able to express the desired pixel type.

As such what about an option like:

creation_options.concatenation = COMPRESS=LERC_DEFLATE
creation_options.filtered      = COMPRESS=LERC_DEFLATE DISCARD_LSB=16 TILED=YES
creation_options.deg_lia       = uint16 COMPRESS=DEFLATE
creation_options.sin_lia       = COMPRESS=LERC_DEFLATE

The proposed format would be:

creation_option.PRODUCT_NAME = [PIXEL_TYPE] GDAL_CO1=VALUE1 GDAL_CO2=VALUE2...

What do you think? About:

• the name creation_options? (I find it long, but explicit, and it refers to GDAL creation options)
• the chosen product names? (they are a bit technical IMO -> concatenation VS S2_product or ...? ; but they are already used for the filename format options)
• the syntax: just an optional pixel type followed by any number of OPTIONNAME=VALUE, and nothing more like &, ?...

mentioned in commit e0daf92c

closed with merge request !101 (merged)