API & MCP
Everything a person can do on Chroma Key: Green Screen to Transparent PNG, a program or AI agent can do with the same inputs and get the identical result.
HTTP API
POST https://luminachromakey.usefulweb.app/api/v1/calculate– run Chroma Key: Green Screen to Transparent PNGGET https://luminachromakey.usefulweb.app/api/v1/tool– inputs, output schema, examples- OpenAPI 3.1: /openapi.json · /openapi.yaml
- Errors:
application/problem+json;422includes per-fielderrors.
Chroma Key: Green Screen to Transparent PNG
Removes a green, blue or any strongly coloured backing from a photo with a colour-difference keyer, un-mixes the backing colour from soft edges, suppresses spill and returns an RGBA PNG plus the matte. The screen colour is picked from the image border automatically or entered as HEX.
| Field | Type | Default | Description |
|---|---|---|---|
image (required) | file | — | Photo in front of a screen (PNG, JPEG or WebP, up to 2 megapixels) |
key | text | "auto" | Screen colour (HEX, or auto = median of the border) |
gain | number | 1 | Screen gain. Above 1 removes more of the screen (also from greenish foreground); below 1 keeps more. |
clipBlack | number | 0 | Clip black. Matte values below this become fully transparent (cleans noisy screens). |
clipWhite | number | 1 | Clip white. Matte values above this become fully opaque (fills holes in the subject). |
spill | number | 1 | Spill suppression |
balance | number | 0.5 | Red/blue balance. Weight of the first other channel in the colour difference (red for green and blue screens). |
shrink | integer | 0 | Shrink matte (px) |
matteBlur | number | 0 | Soften matte edge (px) |
Every result contains
inputs (normalised, defaults applied), summary, result (validated against the published schema), units, assumptions, sources, warnings, computedAt and links.
MCP (Model Context Protocol)
- Streamable HTTP endpoint:
https://luminachromakey.usefulweb.app/mcp– protocol revisions 2026-07-28 (stateless) and 2025-11-25 / 2025-06-18 / 2025-03-26 (initialize handshake). - Tools:
lumina_chroma_key - Local stdio connector:
node src/mcp-stdio.ts --tool=lumina-chroma-key
{
"mcpServers": {
"lumina-chroma-key": { "type": "http", "url": "https://luminachromakey.usefulweb.app/mcp" }
}
}