Colour and OCIO

Oink manages colour with OpenColorIO (OCIO).

The configCopy Anchor Link

• If the OCIO environment variable points at a config, that config is used (Nuke honours $OCIO the same way).
• Otherwise Oink uses the OCIO config that ships in the repository (resources/, the same config Blender 5.2 uses), which includes sRGB, Rec.709, ACES 1.3 / 2.0, AgX and Filmic.

Working spaceCopy Anchor Link

Everything between Read and Write is scene-linear (the config's scene_linear role), 32-bit float, and never clamped. Values above 1 and below 0 survive every node unless a node clamps on purpose.

Read and WriteCopy Anchor Link

• A Read's input transform converts the file to the working space. default picks by file type, using the config's default roles:

  File	default colour space
  float files (EXR, HDR, float TIFF)	scene linear
  log files (DPX, Cineon)	the config's compositing log
  8- and 16-bit integer files (PNG, JPEG, TIFF …)	sRGB

  raw data skips the conversion (for data such as depth or motion vectors).

• A Write's output transform converts back when writing.

• Inside the comp, OCIOColorSpace, Colorspace, OCIODisplay and CDL convert explicitly. OCIODisplay also has gain, gamma and saturation knobs; dragging them is fast because they are applied as live values, not as a rebuilt transform.

• Movie files (MOV, MP4 and the like) use the colour tags stored in the file (transfer and primaries) to pick the input colour space. A movie with no tags is read as Rec.709 with gamma 2.4. Web images (GIF, WebP) count as sRGB.

The ViewerCopy Anchor Link

The Viewer shows the image through a display transform picked in its header: an OCIO display (default sRGB) and view (default the config's default view). The Viewer's gain (exposure in f-stops) and gamma apply only to what you see, never to the comp or to rendered files. Channel buttons, clipping warnings and the pixel readout work on the float values.