[gdal-dev] How to use JPEGXL in TIFF right?

[Rahkonen Jukka]

Hi,

I made some tests about using JPEGXL (JXL) compression in GeoTIFF.  I am interested in lossless compression. So far I have learned that stripes are not good, but results from tiled TIFFs are promising.
The GeoTIFF driver manual has a warning about WEBP compression: "There is a significant time penalty for each tile/strip with lossless WebP compression, so you may want to increase the BLOCKYSIZE value for strip layout." I wonder if the same applies to JPEG XL compression as well. Without tiles this command was very slow
gdal_translate -of gtiff -co compress=jxl p4433h.tif p4433h_jxl.tif
This one was faster.
gdal_translate -of gtiff -co tiled=yes -co compress=jxl p4433h.tif p4433h_jxl_tiled.tif

Not only being slow but the compression with stripes does not really compress much. See the file sizes:

With stripes:  359 211 087 p4433h_jxl.tif
With 256x256 tiles:  142 188 540 p4433h_jxl_tiled.tif
Referense (LZW): 283 864 896 p4433h_lzw.tif

What might be the optimal block size for JXL-in-GeoTIFF when the aim is a good compression ratio and reasonable processing time?

-Jukka Rahkonen-


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