arkennemasis Mask Refine (clean a video mask)

A segmentation model gives you a mask that's almost right, and "almost" is exactly what you can't composite with. Per-frame segmentation is right frame by frame and jittery as a video - the edge boils, a stray blob pops in for two frames, the hairline gets eaten. ArkMaskRefine is the cleanup pass that turns raw segmentation into a mask you can actually cut a subject out with.

The pack's own framing is the best summary: a segmenter is right frame by frame and jittery as a video. Refine it first, composite second. If you're building the avatar pipeline - a presenter cut out of a generated clip and stood in front of an article screenshot - this is the node between the segmenter and the overlay.

How it works

It takes your masks (one per frame) and runs them through a pipeline, in order:

• threshold (0.5) - below this a pixel is background. A soft mask composited straight through shows a grey fringe; thresholding makes it binary.
• keep_largest - drops blobs that aren't the subject. min_area_pct (10) sets how big a component must be relative to the largest to survive, so a limb split off by an occluder doesn't vanish - it's large enough to keep.
• fill_holes - closes enclosed gaps. Turn it off when a genuine hole through the subject must stay transparent.
• grow (1) - expands or contracts the edge by pixels. Segmenters usually cut just inside the subject, so a small positive value recovers the hair line.
• temporal_smooth (3) - averages the mask over N frames. This is the setting that stops the edge boiling, and it's the reason the node exists at all. Keep it small; a fast gesture smears.
• feather (2) - softens the final edge. A hard edge reads as a sticker pasted on the background.

There's also invert for the day a segmenter returns the background instead of the subject, and the report output tells you what it did per frame.

Installing

cd ComfyUI/custom_nodes
git clone https://github.com/Hishamahmer/comfyui-arkennemasis
pip install replicate httpx

Restart ComfyUI (ComfyUI Manager finds it under arkennemasis). It's pure tensor math on your existing masks - no model downloads, no keys.

Troubleshooting

• Edge boils frame to frame: raise temporal_smooth. If it smears a moving arm, lower it - there's a real trade here, and 3–5 is usually the sweet spot.
• Grey fringe around the subject: your mask was soft. Threshold it; that's the setting's job.
• Hair looks cut off: raise grow. Segmenters habitually cut just inside the subject.
• Floating specks and ghost blobs: keep_largest handles most, tune min_area_pct if a real part keeps disappearing.
• Then feed the result into ArkOverlaySubject, which composites it. Refine before overlay - that's the intended order, and the overlay's tooltip says the same thing.