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compositor-mcp

mcp
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SUMMARY

MCP server for Compositor, the open-source Photoshop alternative for Mac: let Claude read and edit .comp projects

README.md

compositor-mcp

An MCP server that lets Claude and other AI agents read and edit
Compositor projects, the open-source Photoshop
alternative for Mac.

It works on the documented .comp package format (a manifest.json plus one PNG per layer), so it
needs no changes to Compositor itself. Edit a project with an agent, then open it in Compositor.
Or the other way round: save in Compositor and let the agent inspect, retouch or render it.

What the agent can do

Tool Purpose
inspect_project Canvas size, resolution and every layer with folder depth, opacity, blend mode, transform, mask and clipping info
list_layers Compact top-to-bottom view like the Layers panel
render_preview Flattened PNG preview returned as an image so the model can see the composition
export_flattened Full-resolution PNG or JPEG export
export_layer Copy a layer's source pixels or mask to a file
create_project New document, optionally with a solid background layer
add_image_layer Import PNG, JPEG, HEIC, TIFF, WebP… as a layer, with fit/fill/stretch placement, opacity, blend mode and folder
add_folder Create a layer folder
set_layer Rename, show/hide, opacity, blend mode, position, size, rotation, flips, sampling, mask on/off
move_layer Reorder layers or move them between folders
remove_layer Delete a layer or a whole folder
replace_layer_image Swap a layer's pixels (round-trip through another tool or a generated image)
set_layer_mask Attach a grayscale mask, invert it, or clear it
resize_canvas Change the document size with an anchor, without resampling
open_in_compositor Open the project in the Compositor app

The server also exposes a compositor://format resource describing the file format.

Related

marcushorndt/compositor-mcp takes a different route: it drives
Compositor's own document model and renderer headlessly (Swift), so previews match the app exactly. This package is a
plain Node server that works on the documented file format, needs no build of the app, and runs wherever Node runs.
Pick whichever fits your setup; both open the same .comp files.

Install

Requires Node.js 20 or later. Compositor itself is only needed to look at the result.

Claude Code

claude mcp add compositor -- npx -y compositor-mcp

Claude Desktop

Add to claude_desktop_config.json:

{
  "mcpServers": {
    "compositor": {
      "command": "npx",
      "args": ["-y", "compositor-mcp"]
    }
  }
}

From source

git clone https://github.com/Josusanz/compositor-mcp
cd compositor-mcp
npm install
npm run build
claude mcp add compositor -- node /path/to/compositor-mcp/dist/src/index.js

Example session

Create a 1920×1080 project at ~/Desktop/poster.comp with a white background, add photo.jpg
scaled to fill, put logo.png in the bottom right corner at 80 % opacity with Multiply, then show
me a preview and open it in Compositor.

The agent calls create_project, add_image_layer twice, set_layer, render_preview and
open_in_compositor. Compositor opens the document with the layers ready to keep editing.

How it maps to the Compositor format

  • Layer pixels are stored untouched as 8-bit sRGB PNGs; placement, scale, rotation and flips live
    in the layer transform, so edits stay non-destructive.
  • Masks are written as 8-bit grayscale PNGs without alpha, as Compositor requires.
  • Manifests are validated against the same rules as ProjectStore.swift before writing, written
    with sorted keys and replaced atomically.
  • Fields this tool does not understand (adjustments, effects, text, shapes, guides, anything newer)
    are preserved on round trip.
  • Projects are saved as format version 9 (what Compositor 1.2.6 writes); a project declaring a newer version keeps its own number and its unknown fields on round trip. Older Compositor builds reject
    newer versions; update the app if a file will not open.

Limitations

  • The preview renderer covers order, folders, visibility, opacity, transforms, raster masks and
    the blend modes sharp supports. Clipping masks, adjustment layers and layer effects are not
    rendered yet; the tool reports what it skipped. Compositor's own export is the reference.
  • Compositor does not watch files for changes. After the agent edits a project that is already
    open, close and reopen the document (or call open_in_compositor).
  • There is no live connection to the running app: selection, undo history and the viewport are
    session-only in Compositor and out of reach here.

Development

npm install
npm test        # builds and runs the node:test suite
npm run dev     # runs the server from TypeScript with tsx

License

MIT. Compositor is © Robbie Tilton, also MIT.

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