Color Key

The Color Key node removes a colour. Pick the key colour or a luminance range, set how close a pixel has to be, and choose whether the output is the keyed picture, its alpha, or a plain mask.

• Key Mode picks colour or luminance keying
• Output chooses alpha-keyed, mask only, or keyed plus alpha
• Found in the node graph under Post FX → Color FX

The image on the right is the example patch itself. Drag and drop it onto the app, or load it with File → Load, to open the full graph. A Caustics field, run through a Gradient Colorizer, keyed against the default green, so nothing is removed until you pick a colour from the palette.

Inputs and outputs

Parameters

Opacity, Blend Mode, and Alpha are the standard operator header; see Parameters and Controls.

• Key Mode — Color (Chroma) (default) matches against Key Color; Luminance (Luma) matches a brightness instead.
• Key Color (default #00ff00).
• Threshold (0–1.74, default 0.3) — how far from the key a pixel can be and still key out.
• Softness (0–1, default 0.1) — width of the feathered edge past the threshold.
• Invert Mask (default off) — keep the keyed pixels and drop the rest.
• Output — Alpha-Keyed (default) makes keyed pixels transparent; Mask Only outputs the white-on-black mask; Keyed + Alpha outputs the picture with the key colour removed and the mask in alpha.

Every slider has a per-parameter animation bar, so it can be animated, audio driven, or MIDI mapped.

Examples

Green screen — a Webcam into Color Key with the defaults, then a Composite over a generator.

Cut out the dark — Key Mode Luminance, Threshold 0.2, so black areas become transparent.

Troubleshooting

Everything keyed out — Threshold is too high for the source's colour spread. Lower it, then raise Softness for a clean edge.

The transparency is not visible downstream — the next node must respect alpha. Use a Composite or Blend to see it over another layer.

Related