exr-io.md

EXR I/O Nodes (MEC)

Two nodes for reading and writing OpenEXR images, under MaskEditControl/IO. Both ship with a fallback chain so they work without extra dependencies — the EXR libraries are only loaded when the node actually runs.

Backend priority

1. OpenEXR + Imath — fastest, full feature set.
2. imageio (with the freeimage plugin if available).
3. TIFF fallback on save — when neither backend can write EXR, a 16-bit TIFF is written next to the requested path with a _fallback.tif suffix and a warning logged. The original .exr file is not silently created.

Install the OpenEXR backend with:

pip install OpenEXR Imath

LoadEXRMEC

Loads a single EXR file and returns it as IMAGE of shape [1,H,W,3] in scene-linear float32. The R, G, B channels are pulled by name; an EXR missing any of those channels raises a clear ValueError.

The info_json output contains backend, width, height, and the file basename.

SaveEXRMEC

Saves an IMAGE batch as one EXR per frame. With a single frame, the output path is used verbatim; for batches an _NNNN suffix is appended (4-digit, 1-indexed).

half_float=True writes EXR-half (recommended; smaller files with no visible quality loss for SDR content). Disable for 32-bit float when storing HDR output for compositing.

See also

• EXRMetadataReaderMEC — pure-python EXR header reader for shot-metadata workflows that only need the header (channels, dataWindow, custom attributes).