Merge Image List

ComfyUI has two different shapes for "a bunch of images": a batch, which is one tensor with everything stacked together, and a list, where the graph processes each item separately and reconverges later. They're not interchangeable - plenty of nodes that expect a batch will choke on a list, and vice versa - so converting between them is its own small category of utility node. Merge Image List is AInseven's entry in that category, and the pitch is right there in the changelog: "the 'Image List to Image Batch' node in my example is too slow, just replace with this faster one." If you've been using whatever list-to-batch node came bundled in an example workflow (a common one ships in Impact Pack, among others) and it's dragging on long sequences, this is a drop-in swap.

How it works

There's no algorithm to explain here beyond the obvious: it takes a list of images coming down the wire and stacks them into a single batch tensor. The value isn't in doing something clever - it's in doing that specific, boring operation faster than the alternative most people already have installed. If you're feeding a long video sequence through it - which is the exact use case this pack is built around - that speed difference actually shows up.

The inputs and outputs that matter

There's really only one input and one output, which is the whole appeal:

• images (IMAGE) - wire in an image list output from anywhere upstream: a Load Images node set to output a list, the results of a For Loop, or the list output of the pack's own reBatchImage node after you've run FastBlend on each chunk.
• Output: IMAGE, as a single batch (is_list: false) - ready to hand straight to Save Image, Video Combine, or any other node that expects one stacked tensor instead of a list it has to iterate.

How to install it

Ships in the same pack as SmoothVideo, InterpolateKeyFrame, and the rest. Via ComfyUI Manager: search "ComfyUI-fastblend," install, restart. Manually:

cd ComfyUI/custom_nodes
git clone https://github.com/AInseven/ComfyUI-fastblend

Restart ComfyUI. Nothing to download - it's a pure batching utility, no models, no external dependencies beyond the pack's own code.

Common issues & troubleshooting

Nothing comes out, or the node errors immediately. Double-check the upstream node is actually outputting a list, not a batch - a batch input here won't have anything to merge because there's nothing to iterate.

Frame order looks off in the final video. List-to-batch converters generally preserve the order they received items in, but it's cheap insurance to spot-check your first and last frame against what you expect before you commit to a long render - especially if the list passed through a For Loop or a chunking node like reBatchImage first, where an off-by-one in how you recombine could shuffle things.

You're not sure if you actually need this over the node you already have. If your list-to-batch step isn't a bottleneck - a short clip, a handful of frames - the built-in alternative is fine and there's no reason to add another dependency. This one earns its keep specifically on long sequences where the naive combiner is visibly slow.