Composite Batch

Another node in WJNodes' options-chain family for its ImageCompositeMask_adv compositor (start with Composite_Basic if you haven't seen how these chain together yet). This one solves a specific, very common headache: your background is one batch size, your surface layer is another, and your mask is a third - which frame goes with which?

How it works

batch_mode picks the reconciliation strategy:

• auto - matches automatically based on the current batch sizes; the default, and the one to leave alone until you have a reason not to.
• flatten - collapses multiple images in a batch down into a single image by stacking them via the alpha channel, rather than keeping them as separate batch items.
• first / last - use just the first or last image in the batch, ignoring the rest.
• match_back / match_surface / match_mask - force the batch count to match whichever of the three you name, adjusting the others to fit.

batch_start and batch_end let you slice a sub-range out of the batch before any of that reconciliation happens - batch_end set to -1 (the default) means "through the end," so you only need to touch it when you want to cut the batch short.

One detail worth knowing: per this node's own description, its settings default to affecting surface and the mask (MaskMix), not back - same default scope as the rest of this options family. Use Composite_Application_pro if you need batch handling to apply to back instead.

The inputs and outputs that matter

• batch_mode (default auto) - the reconciliation strategy, from the list above.
• batch_start (default 0) - start index of the slice.
• batch_end (default -1) - end index; -1 means to the end of the batch.
• Options (optional) - the chain to extend.
• Composite_Basic (output) - the updated chain.

Installing it

Via ComfyUI Manager: search ComfyUI-WJNodes, install, restart. Or:

cd ComfyUI/custom_nodes
git clone https://github.com/807502278/ComfyUI-WJNodes.git
cd ComfyUI-WJNodes
pip install -r requirements.txt

No unusual dependency for this node.

Common issues & troubleshooting

Composite only uses one frame when you expected a full batch. Check batch_mode - first and last are both legitimate settings for deliberately picking one frame, but they're also easy to leave selected by accident after testing with a single-frame case.

Batch counts still don't line up downstream. auto mode makes a best-effort match, but it can't invent frames that don't exist. If your surface batch is genuinely shorter than your back batch and you need every back frame covered, pick match_back explicitly rather than relying on auto to guess what you want.

Slicing with batch_start/batch_end produces an empty result. Double check the indices against your actual batch size - batch_end accepts -1 for "to the end" but a positive value larger than your batch, or a batch_start past your batch length, will legitimately produce nothing rather than clamping silently.

Changes here don't seem to affect the background layer. That's the default scope again - this node's settings apply to surface and mask by default, not back. Reach for Composite_Application_pro if that's what you actually need.