How to read a GeoTIFF file and return in a specific datatype in R language?

Question

I am trying to read a large GeoTIFF file (18000×18000×40) of unsigned byte data format in R by raster package. I hope to read it as raw datatype (unsigned byte) in R, which then will be process by Rcpp.

However, it seems that functions of raster package only return the data as numericdatatype (8-byte float) that will exceed the memory of my machine.

Are there any approach can read the GeoTIFF file and directly return the data as raw datatype in R?

Answer 1

You could read the data in chunks. For example layer by layer, but you could also read the values by block (a subset of rows/columns, but all layers) depending on how you want the data organized for processing. Then for each chunk change the datatype. See terra::readValues or the equivalent in "raster".

You can also have a look at vapour::vapour_read_raster and vapour::vapour_read_raster_raw