Turn image transparency, brightness, or a locally segmented foreground subject into a reusable grayscale mask.
Where: Flowgen → Add → Image & Vector → Matte → Mask Extractor
Key ideas
- Mask Extractor is one graph step: Turn image transparency, brightness, or a locally segmented foreground subject into a reusable grayscale mask.
- Typed sockets: Inputs: Image / image_in — one source image.. Outputs: Mask / mask_out — a grayscale mask where white is selected and black is excluded.. Settings stay on the node rather than masquerading as extra wires.
- Card and Properties agree: The compact card and selected-node Properties sidebar expose the same persisted controls: Source: Alpha, Luminance, or Subject.; Threshold and Softness — visible for Luminance..
- Execution behavior: This browser-local pure operation previews automatically after a short pause while a control changes, then overwrites one durable result file after the value settles. Deselecting the card or starting a downstream flow flushes the pending save. A terminal error exposes Retry; there is no normal Run button.
- Cost and privacy boundary: It calls no generation provider and charges no Sparks/Flowies. Processing happens in the open browser, so it cannot execute in a headless/server-only flow and the source must be readable by the page.
- Mask Extractor card: PureOpNode uses the authored shared-card path. Create a mask from alpha, luminance, or local subject segmentation.
- Properties sidebar: Card-owned operation controls; common properties shell
- Opened surfaces: Mask preview
Steps
- Connect an image.
- Choose Alpha for existing transparency, Luminance for brightness selection, or Subject for the main foreground.
- For Luminance, tune Threshold and Softness.
- Inspect hair, glass, smoke, and semi-transparent edges.
- Refine with Matte Grow / Shrink when needed.
- Connect Mask onward.
Inputs
- Image / image_in — one source image.
Outputs
- Mask / mask_out — a grayscale mask where white is selected and black is excluded.
Controls
- Source: Alpha, Luminance, or Subject.
- Threshold and Softness — visible for Luminance.
Important behavior
- Alpha copies coverage already embedded in the source.
- Luminance converts brightness into the mask and exposes Threshold/Softness.
- Subject runs browser-local foreground segmentation and does not require a text prompt.
MCP authoring
- Create with create_node { type: "maskExtract" }.
- Connect exact handles with connect_nodes when the node has more than one input or output.
- Use set_props with the complete opParams bag and let the open Flowgen client preview/save it; there is no normal run_node step.
Mask Extractor controls and presets
- Add path: Flowgen → Add → Image & Vector → Matte → Mask Extractor.
- Card: PureOpNode.
- Properties: Card-owned operation controls; common properties shell.
- Controls: Alpha; Luminance; Subject; Threshold; Softness.
- Opened surfaces: Mask preview.
Tips
- Test the operation on one representative asset before placing it inside a List iteration.
- Keep the untouched source upstream so the operation can be changed or bypassed later.
- Judge edges and color at the intended delivery size as well as at full preview size.
Limitations and important notes
- Subject finds a foreground, not an object named by text.
- Complex multi-subject scenes may need Mask by Text or Object Select.
Troubleshooting
The mask selects the background
Use Invert downstream or switch the extraction source; Luminance follows brightness, not semantic foreground.
FAQ
Does this open the full Image Editor?
No. This is a focused Flowgen node. Use Image Editor when you need layers, selections, paint, paths, or several edits in one document.
Can I use it in a List iteration?
Yes. Wire the current row field into the typed input, collect the exact output handle, and test one row before scaling the run.