Multi Image Overlay - Sequential Layer Compositing

Node Purpose: Multi Image Overlay overlays multiple image layers sequentially. RGBA inputs use the alpha channel for normal layer compositing, while RGB inputs are treated as opaque layers. If any input contains alpha, the node processes everything in RGBA and automatically outputs RGBA. Supports dynamic input ports image_1..image_N, multiple fit modes, and two batch modes (parallel / stack).

Inputs

Name	Port	Type	Default	Range	Description
`fit_mode`	-	COMBO	`center`	`top_left` / `center` / `stretch`	Size fitting mode.
`color`	-	STRING	`1.0`	gray/HEX/RGB	Background color used when the composited result has no alpha (all-RGB inputs).
`batch_mode`	-	COMBO	`parallel`	`parallel` / `stack`	Batch handling. `parallel` composites corresponding batch indices frame-wise; `stack` flattens every batch item into a single layered preview.
`image_1..image_N`	-	IMAGE	-	-	Dynamic image layers where `image_1` is the topmost layer and larger indices go further down.

Outputs

Name	Type	Description
`image`	IMAGE	Composited image(s); a single preview in `stack` mode, or a batch in `parallel` mode.

Features

Dynamic ports: inputs starting with image_ automatically expand; image_1 is the topmost layer and larger suffixes are placed further below.
Size alignment: uses the bottom-most image dimensions as the base canvas size.
Channel rule: if any input has alpha, all layers are composited in RGBA and the output automatically keeps alpha.
Fit modes:
- center: centers the overlay, cropping excess and leaving gaps transparent.
- top_left: aligns the overlay to the top-left corner.
- stretch: stretches the overlay to match the canvas size.
Batch modes:
- parallel (default): broadcasts smaller batches and composites corresponding indices in parallel, with image_1 on top and image_N at the bottom.
- stack: treats every item in every input batch as one layer and produces a single preview image; within each batch the first item is the top item.
Alpha compositing: correctly handles premultiplied alpha blending for RGBA images. RGB images are treated as fully opaque.

Typical Usage

Image compositing: overlaying multiple elements with transparent backgrounds (e.g., stickers, watermarks, foreground subjects) onto a background image.
Batch overlay: use batch_mode=parallel to composite corresponding frames across batches (broadcasting smaller batches to the maximum size).
Single preview: use batch_mode=stack to flatten all frames of every input into one layered preview image.

Notes & Tips

Higher-numbered inputs are better suited for background/base layers, while image_1 is better used for the top layer.
To keep transparency for downstream nodes, make sure at least one input already carries alpha.

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