Dilate Mask Regions

Probably the single most commonly needed operation in this whole mask-filter family, if you've ever done any serious inpainting. A mask that fits your subject exactly, pixel-perfect, actually inpaints worse than one with a little breathing room - the model needs some margin around the edge to blend new content in cleanly, which is why growing or feathering a mask before inpainting shows up in basically every real workflow. Dilate Mask Regions does the growing side of that.

How it works

This is straightforward morphological dilation - a core OpenCV operation (dilate) - that expands the white, masked region outward in every direction, roughly one pixel-ish per iteration. There's no separate "amount per pass" to configure; iterations is the whole control surface. It's a close cousin to mask blur/feathering (typically applied in the 4–12px range in most inpainting workflows), except dilation grows the hard region itself rather than softening the edge - you often want both, growing first and then softening.

The inputs and outputs that matter

• masks (required, MASK).
• iterations (required, default 5, 1–64) - higher grows the mask more. Default 5 is a modest expansion; nudge it up if you're still seeing hard seams at the mask edge after generation.

Output is MASKS, the grown region.

How to install it

ComfyUI Manager: search SaltAI-Open-Resources or SaltAI, install, restart. Manual:

cd ComfyUI/custom_nodes
git clone https://github.com/get-salt-AI/SaltAI

then restart. OpenCV-backed (dilate is a core cv2 morphology op), no model download.

Common issues & troubleshooting

Grew the mask into territory that was supposed to stay untouched. Too many iterations for the image size - a handful of iterations covers a much bigger fraction of a small image than it does on a 4K source, so subject regions that were meant to stay protected start getting swept into the inpaint area. Scale iterations to your resolution, not to a fixed number you always reach for.

Seams still visible after generous dilation. More dilation alone isn't the fix past a certain point - it just makes the edge bigger, not softer, and dilation on its own still leaves a hard boundary. Pair it with an actual smoothing step afterward, either a blur/feather node or SaltMaskBilateralFilter (softer than a plain blur, since it won't blur away the boundary you just grew).

Mask shape looks blobby, lost fine detail. High iteration counts round off thin protrusions and small gaps - fine for a rough subject region, bad if you needed to preserve something delicate like individual fingers or hair strands in the mask. Drop iterations back down for anything with fine structure.