The itmap istribution ormat is a format for storing bitmapped fonts. It is in simple ASCII. It originated on the X-Windows system but can be made to work on other systems as well. It is a product of Adobe.

Bi-directional ( scattering ) distribution function describes the directional distribution of scattered light ( either reflected or transmitted ). This notion generalizes BRDF and BTDF terms. BRDF Bi-directional reflectance distribution function describes the directional distribution of reflected light. It is defined as the ratio of the radiance ( luminance) of light reflected in the viewing direction and the irradiance ( illuminance) from the incident direction. In the general case, it is a function of both incident and viewing directions. BRDF is expressed in units of inverse steradians. BTDF Bi-directional transmittance distribution function describes the directional distribution of transmitted light. It is defined as the ratio of the radiance ( luminance) of light transmitted in the viewing direction and the irradiance ( illuminance) from the incident direction. In the general case, it is a function of both incident and viewing directions. BTDF is expressed in units of inverse steradians.

fonts are a variety of bit-mapped fonts that may be used with X.

Bitmap distribution format files are ASCII files that describe a bitmap font. They are frequently used to distribute bitmap versions of scalable fonts in screen resolution at common sizes. They are resolution specific, but they are portable from one architecture to another. The BDF file format is described completely in Adobe's BDF Format Specification [ bdffiles]. Some fonts packages are distributed with BDF files. Other BDF files are created as part of the conversion process from native format to X11 format. It is unlikely that you would ever create one purely by hand.