May 26, 2018
High dynamic-range (HDR) image file format
OpenEXR is a high dynamic-range HDR image file format developed by Industrial Light & Magic for use in computer imaging applications.
OpenEXR is used by ILM on all motion pictures currently in production. The first movies to employ OpenEXR were Harry Potter and the Sorcerers Stone, Men in Black II, Gangs of New York, and Signs. Since then, OpenEXR has become ILM’s main image file format.
OpenEXR’s features include
- Higher dynamic range and color precision than existing 8- and 10-bit image file formats.
- Support for 16-bit floating-point, 32-bit floating-point, and 32-bit integer pixels. The 16-bit floating-point format, called “half”, is compatible with the half data type in NVIDIA’s Cg graphics language and is supported natively on their new GeForce FX and Quadro FX 3D graphics solutions.
- Multiple lossless image compression algorithms. Some of the included codecs can achieve 21 lossless compression ratios on images with film grain.
- Extensibility. New compression codecs and image types can easily be added by extending the C++ classes included in the OpenEXR software distribution. New image attributes strings, vectors, integers, etc. can be added to OpenEXR image headers without affecting backward compatibility with existing OpenEXR applications.