Portable Float Map is unofficial extension of PNM format family which can store images with floating point pixels.

public TPFMFileFormat = class(TPortableMapFileFormat);

ImagingPortableMaps (at line 135)

Raster data is saved in binary format as array of IEEE 32 bit floating point numbers. One channel or RGB images are supported by PFM format (so no alpha).

TObject
TImageFileFormat
TPortableMapFileFormat
TPFMFileFormat