ExR

EXR is a high dynamic range image file format developed by Industrial Light & Magic (ILM) for use in digital imaging, visual effects, and computer graphics. The file extension is .exr and EXR images are stored and manipulated using the OpenEXR software library, an open-source project released by ILM.

Key features include support for multiple channels per image (for example R, G, B, A, and arbitrary custom channels), tolerance for very wide color gamuts and high bit depths, and optional support for deep data (per-pixel multiple samples along depth). The format supports both tiled and scanline-based images, enabling efficient access at various resolutions and progressive rendering workflows. EXR also provides extensive metadata and a flexible attribute system to store scene data alongside pixel values.

Pixel data types primarily use 16-bit half or 32-bit single-precision floating point values, with optional integer types in some channels. The format supports a range of compression methods, including RLE, ZIP, PIZ, PXR24, and B44/B44A, which vary in speed and lossiness to balance image quality and performance.

OpenEXR has been adopted widely in feature film production, visual effects, and game pipelines. Software support spans major 3D graphics packages, compositing tools, and imaging libraries, with the OpenEXR library providing read and write functionality across platforms. The format is designed to be extensible, prioritizing data fidelity and interoperability in professional workflows.