Using BioFormats import options, we can define a C Z and T step when importing data, so as to only get a subset.
Unfortunately, there is not a possibility to define an XY step to take just 1 pixel out of 4, for example.
Sometimes this is useful when people want to extract a select part of their data to look at it for example.
The following Groovy script https://gist.github.com/280654785f7a2a79a5093997b50d92bf
Works on multi-series files and saves the XYCZT data to tif (1 tif -> 1 plane) with the selected resizing in XY and Z
It is simple but fast (23s for a 17GB file resampled 2x in XY and 10x in Z). Maybe someone else can have a use for it.