The XRH file format (with .xrh file name extension) is a simple standard royalties-free file format for storing and archiving extended dynamic range raster image data.
XRH stores higher precision extended range still images. The images could be any spatially correlated rectangular raster data, such as photographs, or geographic elevation data, etc. Each image contains one or more channels (also called image planes or components).
Extended dynamic range images are images that store more than 8 bits per channel. The number of bits per channel is called precision. Extended range images have higher precision.
Color sample values are stored as natural (linear) color values, because higher precision makes sample values more dense (eliminating the need to nonlinearly spread sample values).
The XRH file format is intended to be used for data transfer, processing and archiving purposes, not as a motion picture format.
In an XRH file, each image channel of samples is stored compressed. Each channel can have its own Compression Type. The following Compression Types are currently supported:
Zebra is a lossless compression method using
to store Byte Channels of multi-byte samples:
four Byte Channels per
SZMOD is a lossy compression method
that directly compresses
JP2K is a lossy compression method
In theory, the JPEG 2000 standard
allows sample precision to be higher
than 24 bits per channel.
But in practice,
current JPEG 2000 implementations
only support up to 24 bits per channel.
This XRH version defines a method
Free proof-of-concept C source code for reading and writing XRH files is provided with Example Images (see below).