ii_map_rebin reads input background and/or Off-axis correction maps and rebins them into new energy bands. Background maps are summed with coefficients equal to the part of each input map that participates in the sum. Off-axis maps are also weighted by a power-law spectrum (with the default slope -2) and ARF (if present). After rebinning, off-axis maps are normalized to 1. Output energy bands are defined from the index of detector shadowgrams (ISGR-DETE-SHD) of a given type.