IncompatibleBlockRasterSize check purpose

[tyler-c2s]

👋 hi all,

I am curious to dig into the IncompatibleBlockRasterSize check that exists in rio-cogeo for small 2D dimension files (e.g. 34x29 px)

I have run across tools (in my case Google EarthEngine) that are only happy to accept COGs, but check if the file is Tiled as part of COG validation. This will fail if rio cogeo create with default settings as it will not write blocks due to the dimension size check, and thus the file reports in rio cogeo info as a valid COG, but False under Tiled. If you specify a block size, you get IncompatibleBlockRasterSize exceptions.

Profile
    Width:            34
    Height:           29
    Bands:            1
    Tiled:            False

...

IFD
    Id      Size           BlockSize     Decimation           
    0       34x29          34x29         0

GDAL does not seem to care, and if you gdal_translate --of COG it will write a TIFF w/ the default BlockSize, extra space on disk required and all.

Profile
    Width:            34
    Height:           29
    Bands:            1
    Tiled:            True

...

IFD
    Id      Size           BlockSize     Decimation           
    0       34x29          512x512       0

My understanding has always been that to lay your data out in a tiled format, you have to write more TiffTags which may end up costing more in storage sapce, when writing data with small dimensions (e.g. 32 x 32 px). Should a COG be considered valid if it is not Tiled? Is there a reason why to enforce skipping writing in a tiled format even for small images?

Curious to hear what others thoughts are

[geospatial-jeff]

My personal opinion is that all COGs should be tiled even if they are small. The storage overhead of writing extra tiff headers is so small it doesn't matter too much (storage is cheap), especially considering most readers aim to fetch the entire TIFF header in one range request (usually ~16-64kb).

COG compliant software (readers / writers / validators etc.) will be much simpler if they only have to support tiled images, instead of tiled and strip.

[vincentsarago]

rasterio has just been updated: rasterio/rasterio#2615 and it changes everything. I'll update rio-cogeo

[vincentsarago]

side note:

Usually if a file is < 512px we don't require it to be tiled to be accepted as a COG

https://github.com/OSGeo/gdal/blob/master/swig/python/gdal-utils/osgeo_utils/samples/validate_cloud_optimized_geotiff.py#L195-L199

[vincentsarago]

This should now be fixed. with rio-cogeo>=3.5