Image Blend BG

A two-image compositor built specifically around the background/foreground relationship: one image is explicitly the background, one is explicitly the thing going on top of it, and you get to control both where it lands and how strongly it blends in.

What it's for, and how it differs from the pack's other blend nodes

This pack ships several image-combining nodes, and it's worth knowing where each one fits. Multiple Image Blend and its v2 sibling treat every input as an equal layer with one shared opacity. Batch Image Blend flattens an entire batch into one. This node is different again: it has exactly two image roles - image_bg and image, background and foreground - plus an alignment control for placement and an opacity control for blend strength. It's the node to reach for when the relationship between your two images genuinely is "one sits on top of the other," rather than "average these together."

A typical use: you've generated or sourced a background plate, and you want to drop a rendered subject onto it - positioned via align, blended in via opacity rather than pasted as a hard cutout. If you need a hard paste with pixel-precise positioning instead of a blend, this pack's separate Image Align node is the better fit; that one skips opacity entirely in favor of exact offset control.

Inputs and outputs that matter

• image_bg (required) - the background layer.
• image (required) - the foreground layer, composited onto the background.
• align (required, dropdown: size, top left, center) - governs how the foreground is positioned relative to the background when the two aren't the same size. size likely scales the foreground to match; top left and center anchor it at that position instead.
• opacity (required, 0–1, default 1, step 0.01) - how strongly the foreground blends into the background. At 1 it's fully opaque over the background; lower values let the background show through.

The output is a single image - the composited result.

Installing it

ComfyUI Manager: search ComfyUI-ReplenishNodes, install, restart. Or manually:

cd ComfyUI/custom_nodes
git clone https://github.com/hben35096/ComfyUI-ReplenishNodes

No model downloads or extra dependencies documented for this node.

Where people get tripped up

Confusing which slot is which. image_bg and image are not interchangeable - swap them and you'll composite your intended background onto your intended foreground instead of the other way around, which usually looks obviously wrong but isn't always. Double-check the wiring if a composite comes out inverted from what you expected.

Expecting alpha-aware compositing on an image with transparency. If your foreground image has a transparent background (from a matting or background-removal step, say) and you actually want that transparency respected during the composite rather than blended at a flat opacity, check the result carefully - this node's fields only describe an opacity blend, with no separate control mentioned for treating an existing alpha channel differently. If your source has transparent regions you want flattened first, this pack's Fill Alpha node is built for exactly that step.

Picking align blind. As with the pack's other alignment-aware blend node, there's no live preview of what each option does to your specific images - test on one image before committing to a full batch.