Image Infill Boundary Propagate

Sometimes you don't need a smart fill - you need a fill. Image Infill Boundary Propagate is the simplest infill in the illumorae pack: it fills a masked region by propagating colors inward from the region's boundary, one ring of pixels at a time, like peeling an onion in reverse. No model, no patch search, no statistics. Just the pixels you already have, smeared sensibly into the hole.

Why reach for it? It's a prep step, not a finish. If you're about to run real inpainting or an edit model over a masked area, a plain fill often gives you better results than feeding the model a hard black hole - the model can see the surrounding colors instead of guessing at empty space. Boundary propagate is also genuinely good at outpainting-ish background extension where the region is a smooth gradient (sky, walls, flat ground) and the fill doesn't have to invent structure. And it's fast. Millisecond-fast.

How it works

The mask defines the target region, and the node works in from the boundary one 8-connected ring at a time. The important design choice is that each frontier pixel gets a random-weighted average of its already-known neighbors rather than a deterministic max-filter dilation - the randomness is what stops the streaky, ridge-like artifacts that naive inward blurring produces. It's the classic Criminisi-style terminology (target region vs. source region) but with none of Criminisi's sophistication: no priority, no structure propagation, just color.

The inputs you'll actually set:

• mask and mask_mode - auto guesses which polarity means "fill," or you can force white=fill or black=fill if the mask comes in flipped. This is the #1 thing to check when the fill fills the wrong area.
• propagate_iterations (default 50) - how many rings to propagate; basically the radius of the largest hole it can fill. Too low and the hole isn't closed.
• use_center_blend / center_blend_strength - blends the final center with a blurred average, which cleans up the middle where the propagation has no real signal left.
• blur_center / blur_strength / blur_falloff_distance - softens the fill; and feather_amount blends the fill edge back into the original so it doesn't look pasted.
• use_angular_drift / drift_radius - the randomness control; more drift = smoother but less faithful fills.

Outputs: infilled_image plus two diagnostic visualizations - distance_map_viz (how many propagation steps each pixel is from the boundary) and blur_weight_viz (where the center blur is applied). Both are for eyeballing behavior, not for wiring downstream.

Installing it

Part of CorvaeOboro's ComfyUI_illumorae (CC0, pure code). ComfyUI Manager → search illumorae, or:

cd ComfyUI/custom_nodes
git clone https://github.com/CorvaeOboro/ComfyUI_illumorae

Common issues

• The fill goes into the wrong region - mask polarity. Check mask_mode and flip white=fill/black=fill.
• Big holes stay black in the middle - propagate_iterations too low for the hole size, or use_center_blend off when it should be on. This is a propagation fill; holes bigger than your iteration budget simply don't get reached.
• It's not meant for structure - if you're filling across a wall/road/horizon, this node will smear a gradient and look wrong. That's what the pack's Exemplar Region Fill or PatchMatch nodes are for. Reach for boundary propagate on smooth fills only.