Apply a connected grayscale mask to an image as its alpha channel, with optional inversion and feathering.
Where: Flowgen → Add → Image & Vector → Matte → Merge Alpha
Key ideas
- Merge Alpha is one graph step: Apply a connected grayscale mask to an image as its alpha channel, with optional inversion and feathering.
- Typed sockets: Inputs: Image / image_in — the visible RGB image.; Mask / mask_in — the coverage matte.. Outputs: Image Output / image_out — an image carrying the merged transparency.. 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: Invert mask.; Feather: 0–64 px..
- 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.
- Merge Alpha card: PureOpNode uses the authored shared-card path. Apply a grayscale mask to an image as alpha.
- Properties sidebar: Card-owned operation controls; common properties shell
- Opened surfaces: Transparent image preview
Steps
- Connect the source image and mask.
- Toggle Invert if the wrong region remains visible.
- Add only enough Feather to integrate the edge.
- Preview over a contrasting background.
- Inspect transparency, not only the card checkerboard.
- Connect Image Output onward.
Inputs
- Image / image_in — the visible RGB image.
- Mask / mask_in — the coverage matte.
Outputs
- Image Output / image_out — an image carrying the merged transparency.
Controls
- Invert mask.
- Feather: 0–64 px.
Important behavior
- White mask pixels keep the image opaque and black pixels make it transparent.
- Invert reverses that relationship.
- The output keeps RGB pixels and packages the matte as image alpha for downstream editors and renders.
MCP authoring
- Create with create_node { type: "mergeAlpha" }.
- 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.
Merge Alpha controls and presets
- Add path: Flowgen → Add → Image & Vector → Matte → Merge Alpha.
- Card: PureOpNode.
- Properties: Card-owned operation controls; common properties shell.
- Controls: Invert mask; Feather.
- Opened surfaces: Transparent image 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
- The image and mask are flattened into one output.
- Use Blend when you need a second visible image rather than transparency.
Troubleshooting
The subject disappears
Toggle Invert. The default convention is white keeps and black removes.
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.