hdftopal converts a palette in an HDF file to a raw
palette in an non-HDF file. The raw palette will have 768 bytes with
the first 256 bytes representing red intensity values, the second 256
bytes representing green intensity values, and the third 256 bytes
representing blue intensity values.
paltohdf performs the converse conversion, from raw palette data
to the HDF palette format. The raw palette data must have 768 bytes
organized in the following order: first, 256 contiguous red intensity
values, then 256 contiguous green intensity values, then 256
contiguous blue intensity values. The palette in the HDF file will
have the RGB values pixel-interlaced, as follows:
This is the standard HDF format for 8-bit palettes.
If an HDF palette format file is specified that doesn't exist, it is
created before the converted data is stored. If an HDF palette format
file is specified that already exists, the converted data is appended
to the file.