Alternative University

Computer Science

Raster Image Storage

Higher Precision Extended Range

XRH File Format 1.0

The XRH file format (with  .xrh  file name extension) is a simple standard royalties-free file format for storing and archiving extended 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 range (XR) images are images that store more than 8 bits per channel. Legacy extended range formats primarily store images that are 16 or 24 bits per channel. XRH files store images that are 32 bits or 64 bits per channel.

Each value (sample) stored in a channel in an XRH file is a floating point number (FLOAT32 or FLOAT64).

In an XRH file, each channel of floating point numbers is stored compressed. The following compression formats are supported for each channel in this version of the XRH file format specification:

  • Zebra lossless compression
  • SZ 2.1.9 lossy compression

Zebra is a lossless compression method using ZST o to store Byte Channels of the 32-bit (or 64-bit) floating point samples, four (or eight) Byte Channels per image channel. 

SZ 2.1.9 is a high quality lossy compression method that is under active development:

“we successfully leverage adaptive parameter optimization techniques with a series of optimization strategies on data prediction, which can significantly improve the compression quality for SZ with the same level of data distortion.”
— 
Kai Zhao, Sheng Di, et al., HPDC ’20, June 23–26, 2020, Stockholm, Sweden [DOI]

Additional compression methods may be added in the future. More information about this file format will be posted.

Free proof-of-concept C source code for reading and writing XRH files is provided in XRHLIB o

The XRH file format is for use royalties-free, including in commercial applications. Disclaimer: No warranties expressed or implied are provided; In no event will this specification’s authors, publishers or anyone associated thereof be held liable for any damages arising from its use.


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XRH File Format
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Introduction (this page)
File Layout & Header
Comments
Custom Properties
Channel Names
Channels
Zebra Compression
SZ219 Compression
Color Transformations

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2020–Oct–26  15:17  UTC