Feature Request: Support for non-green chroma key backgrounds (blue, magenta)

[kkkirin]

Feature Request

Support for chroma key backgrounds other than green (e.g. blue, magenta).

Use Case

I'm building a CEP extension for After Effects that generates decorative text images on chroma key backgrounds using AI (Gemini), then keys them out for compositing.

The problem: when the generated design contains green/teal elements (e.g. ribbons, leaves, nature-themed decorations), green screen keying inevitably removes or damages those elements. Switching to a blue or magenta background for generation would solve this, but CorridorKey currently only supports green screen.

What I've Tried

• Green background + CorridorKey: Best edge quality, but green design elements get partially keyed out
• Channel swap (B↔G) hack: Swapping blue↔green channels before inference so blue backgrounds appear green to the model. The alpha output is usable, but purple/violet colors in the design get misidentified as green-mixed pixels, causing unwanted transparency
• HSV-based keying for blue/magenta: Works but edge quality is significantly worse than CorridorKey's neural network approach

Proposed Solution

It would be great if CorridorKey supported at least blue screen keying in addition to green. Ideally:

• --background green (current default)
• --background blue
• --background magenta

Or alternatively, a way to specify the chroma key color so the model can adapt its unmixing accordingly.

Environment

• macOS (Apple Silicon M-series, MPS backend)
• CorridorKey v1.0
• Using the Python API (CorridorKeyEngine.process_frame())

Thanks for the amazing tool! The edge quality on green screens is outstanding.