exr2aces

exr2aces [options] infile outfile

Description

Read an OpenEXR file from infile and save the contents in ACES image file outfile.

The ACES Image Container File Format specified in SMPTE ST 2065-4 is a subset of the OpenEXR file format defined by the implementation of the time (roughly OpenEXR 1.6).

This imposes considerable restrictions on what image data and metadata can be transported from a modern OpenEXR file into an ACES Image Container File, including (but not limited to) the following:

  • The version field must be either be 2 or 1026; a value of 2 implies attribute names cannot be longer than 31 characters in length, as was the case prior to OpenEXR 1.7.

  • Images must be stored as scanlines; tiles are not allowed.

  • Images must contain RGB and possibly an A channel if they are monoscopic; images representing stereo pairs would add another three (or four if A is present) channels. Other channels are not permitted, including channels that otherwise might represent a combination of a luminance channel and chromaticity channels.

  • The image must not be compressed.

  • The chromaticities attribute must specify the ACES RGB primaries and the ACES neutral as specified in SMPTE ST 2065-1.

  • The acesImageContainerFlag flat must be present and have the value 1.

For the full set of restrictions, see SMTPE ST 2065-4 (or any superseding later version of that standard).

In practice, facilities and productions often use the term “ACES file” to mean OpenEXR files containing linear scene data expressed as combinations of R, G and B whose chromaticities match those found in ST 2065-1, where equal amounts of those primaries produce a color the chromaticity of which matches that of the ACES neutral. The image data might be compressed using one of the OpenEXR’s library’s built-in compression functions, even though strict compliance with ST 2065-4 would forbid such compression; the acesImageContainerFile flag might be missing; and the chromaticities attribute might contain chromaticities that do not actually match those found in ST 2065-1.

Options:

-v, --verbose

verbose mode

-h, --help

print this message

--version

print version information