The HDF_DF24_NIMAGES function returns the number of 24-bit images in an HDF file. A -1 is returned if the specified file is invalid or damaged.
h = HDF_OPEN('myhdf.hdf') ; Open an HDF file.
number = HDF_DF24_NIMAGES('myhdf.hdf') ; Return the number of 24-bit images in the file.
HELP, number ;
Print information about the returned value. If there were five images in the file, IDL would print:
NUMBER LONG = 5
HDF_DF24_GETIMAGE , HDF_DF24_GETINFO , HDF_DF24_READREF , HDF_DF24_RESTART , HDF_DFR8_NIMAGES