Silhouette

Silhouette turns a real green screen into a clean, fast virtual camera for macOS.

Hang a green or blue backdrop, point your camera at it, and Silhouette removes it on the GPU. Pick the "Silhouette" camera in FaceTime, Zoom, Google Meet, Microsoft Teams, or any app that uses a Mac camera.

• Background and foreground layers: images, looping movies, solid colours, or live web pages.
• A soft drop shadow cast by your silhouette.
• Optional on-device face tracking, available to web page layers through a JavaScript API.
• An Apple camera extension: no kernel extensions and no disabled security settings.

Requires macOS 14 or later and a physical green or blue backdrop.

Links

• Support
• Privacy policy
• Terms of use

Building from source

A minimal, GPU-only chroma keyer for macOS that outputs a virtual camera.

• Keys the camera feed in its native YCbCr 4:2:0 planes with one Metal fragment shader. No colour conversion before the key, no CPU copies.
• Background and foreground layers are images, looping movies, solid colours, or web pages (snapshotted up to 15×/s, 3×/s when static). With no background the output is transparent and the preview shows a checkerboard.
• Output is a CoreMediaIO camera extension, the modern replacement for DAL plug-ins. Zoom, FaceTime, Meet, and Photo Booth see "Silhouette" as a camera with no changes to those apps and nothing to disable in macOS.

Build and install

Requires Xcode and brew install xcodegen. The project is signed with the TVA9Z8LD95 team (set in project.yml); change it to yours if needed.

make install

That builds a Release app, copies it to /Applications, and launches it. On first launch macOS asks you to allow the camera extension in System Settings → General → Login Items & Extensions → Camera Extensions. Approve it once; from then on "Silhouette" is available in any video app.

make run launches from the build folder for iterating on the keyer. The virtual camera is only installed from /Applications.

Use

• Auto runs when a source is first chosen: it pools a few frames, finds the dominant colour around the frame edge (skipping the face and the body under it), sets Color Range so the edge is removed and the face is kept, sets Shrink and Blur from the measured fringe, and Desaturate from the tint on the subject. Stabilize is left alone. Each source remembers its key.
• Or click the colour swatch, then click the backdrop in the preview to pick the key colour. The preview shows the unkeyed image while picking.
• Any movie file works as the camera: Source → Video file…, or drop one on the window. The last ten movies stay in the Source menu. It loops, decodes in hardware, and 4K files run the full path.
• Face tracking runs Vision on the Neural Engine. Show on preview draws the landmark contours; High frame rate tracks every frame. Web pages get the data through window.silhouette.on('face', fn): box, centre, yaw, pitch, roll, eyes, nose, mouth, contours, estimated distance, and pose and projection matrices. See the web page API.
• No green screen handy? Pick "Sample video" in the Source menu for a real green screen clip, or "Test pattern" for a synthetic green backdrop with a face shape, fine hair strokes, a soft gradient edge, a moving square, and sensor-like noise.
• Controls live in a sidebar on the preview window (Cmd+K hides it).
• Layers has a Background box and a Foreground box. Each takes None, the test page, a URL, a file path, or a hex colour like #1E90FF (8 digits for alpha). The last ten entries are listed for reuse.
• Color Range is in percent of the chroma span: the low value is fully keyed out, the high value is where the transition ends. The bar shows the colours along that axis. Shrink pulls the matte edge in, in 1080p pixels.
• Desaturate removes green reflections.
• Blur softens the matte edge. Stabilize blends the matte with the previous frame's to stop edge flicker from sensor noise; large changes are treated as motion and pass straight through.
• Vary with distance scales the shadow with the tracked face: nearer gives a longer, softer, lighter shadow; farther gives a shorter, sharper, denser one. Slider values apply at a face 40% of the frame tall.
• Shadow adds a soft drop shadow behind you: the matte rendered at quarter size on a padded canvas, Gaussian-blurred on the GPU, and offset. The switch in its header turns it off; drag the offset pad to position it, double-click to reset. The Chromakey switch turns keying off entirely.
• Drop an image or a URL onto the window, or use the Background menu.
• The preview is mirrored like a mirror; the virtual camera output is not. View → Mirror Preview turns that off, useful when reading a web background.
• 4K keying captures at 3840×2160 when the camera supports it, runs the key, feather, and composite at that size, and box-downsamples to the 1080p output. Finer hair and edges with a 4K camera; four times the GPU work.
• The virtual camera output is always 1920×1080 at 30 fps. The camera and background are scaled to fill it.

Layout

• App/ — the macOS app: capture, Metal renderer, controls, CMIO sink client.
• Extension/ — the camera extension: one device with a source stream (what other apps read) and a sink stream (what the app writes into).
• Shared/ — constants both sides agree on.

Distribute to other Macs

make install signs with your Apple Development certificate, which only runs on Macs registered to the team. For any Mac, use Developer ID plus notarization:

make dist

This archives, exports with Xcode's cloud-managed Developer ID certificate, notarizes, staples, and writes dist/Silhouette.zip. One-time setup before the first run, with an app-specific password from appleid.apple.com:

xcrun notarytool store-credentials GreenScreen --apple-id you@example.com --team-id TVA9Z8LD95

For TestFlight and the Mac App Store, make testflight bumps the build number, archives, signs for the App Store, and uploads to App Store Connect. The version (MARKETING_VERSION) only changes when you mean to start a new App Review version.

Without notarization the exported app still runs on other Macs, but Gatekeeper asks you to allow it in System Settings → Privacy & Security on first launch, and macOS might refuse to load the camera extension.

Sandbox

The app runs in the App Sandbox (camera, outgoing network, user-selected files). Files you pick or drop are remembered with security-scoped bookmarks, so they reopen on the next launch. This is the configuration the Mac App Store requires; Developer ID builds use it too.

Performance notes

• The window's top right shows frames per second and the GPU time per frame for the keying pipeline (also logged under subsystem com.artifact.Silhouette, category stats).
• The window is one Liquid Glass sheet; the preview sits in an opaque box on top of it, so the glass does not recomposite at frame rate.
• Sources are consumed in their native pixel format (video range or full range); the shader normalises, so no conversion pass runs per frame.
• Face tracking works on a 640×360 4:2:0 copy made on the GPU. The detector runs about four times a second; landmarks fit every tracked frame.
• Web snapshots upload straight into a shared texture, skip when nothing changed, and back off to 3 per second while the page is static.

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