[GRASS-user] split a image and merge it?

[maven apache]

is there a procss which can split a image and merge it?
I want to do some grid test for handling some hdf5 data,for example I want
to use the r.fillnulls to handle a hdf5 data, first I transfer it to tiff,
and then impor it to grass, then use r.fillnuls,however it take too long. So
I want to split the hdf5 or tiff to use the r.fillnulls and then merge them
together.
Can this be implemented?
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