FJPG

FJPG is a JPEG flavor that supports display of high dynamic range (HDR) images for PTViewer 3.x introduced by Helmut Dersch. A FJPG file stores an additional block of data containing exponent values for each 8x8 pixel block of the normal JPEG image. This way JPEG is extended into a good compressed albeit a bit coarse HDR image format.

A conversion program, a technical paper and PTViewer 3.1.2 which uses this file format for display of adaptive dynamic range panoramas and images can be found on Helmut Dersch's page: [1]