Preview Image

What it is

Preview Image is ComfyUI's workhorse image preview, rebuilt with Eclipse's conventions. You wire in a batch of images, you see them, and the batch passes out the other side unchanged so the graph keeps flowing. It looks like the stock node and behaves like it - because it is the same pattern, done with the Eclipse pack's polish.

If you're new to ComfyUI, the mental model is simple: preview nodes are the "look at this" stops in your graph. This one is the plain version. The DOM-preview sibling is the fancier rendering; this is the dependable one you drop in when you just want to see what a node produced.

How it works

The mechanism is exactly what the stock PreviewImage does, which is worth understanding because it explains a couple of things people get wrong. The images are written out as PNGs to ComfyUI's temp directory - the scratch folder, deliberately separate from output/ so your previews don't pollute your real saves. Then the UI shows them. The pass-through output means it also functions as a mid-graph checkpoint: preview here, keep the same images flowing to the next node.

The metadata touch is the Eclipse flavor: the temp PNGs get the workflow and prompt embedded into them, same as a save. That means a preview image you drag back onto the canvas reconstructs the graph that made it. It's the "the image is the project file" convention (covered in the image I/O docs) applied even to throwaway previews - handy when a temp preview is all you have left of a run.

One implementation detail worth knowing: the node accepts batches and lists of individual tensors, flattens them, and saves each frame separately, with a progress bar over the batch. It's an output node, so it always executes and the cache works backward from it.

The inputs and outputs that matter

• images (required) - the batch or list of images to preview.

Output:

• IMAGE - the same images, passed through. Wire it onward to keep the workflow going, or leave it unconnected; the preview still displays.

When you'd use it

Everywhere you'd use the stock Preview Image: after a sampler, after an upscale, anywhere you need eyes on intermediate output. The pass-through makes it a zero-cost checkpoint in a longer chain - you get the preview and the workflow continues, no branch required.

Installing it

It's part of ComfyUI_Eclipse:

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

then restart ComfyUI, or install via Manager and search "Eclipse". One warning if you're inheriting old workflows: the pack was formerly RvTools_v2, and v4.0.0 removed all legacy nodes - the bundled Workflow Migration Tool is the fix for graphs that won't load.

Common issues

The failure mode to internalize is the temp/output split. People generate something great, see it in the preview, and hunt through output/ for it - it's not there, because previews write to temp. If you want the file kept, route the pass-through into Save Images (or switch to it). And if you're driving ComfyUI as an API or from a bare environment, remember previews live at ComfyUI/temp - treat them as scratch, because that's exactly what they are.