Preview Image

ComfyUI's built-in PreviewImage is fine until your output isn't a single image. When you're generating a batch - a grid of style tests, an animation frame dump, a face-library sweep - you usually want to see more than the first frame, or you want to preview without the overhead of previewing everything. Preview Image is a drop-in replacement with one extra widget that solves exactly that: Show_Images, which controls how many images of the batch actually get previewed.

How it works

Feed it an images tensor (IMAGE input, which every image-producing node in ComfyUI outputs) and it renders the batch to the preview pane, just like the built-in node. The difference is the Show_Images widget (default -1):

• -1 - preview all images in the batch.
• 0 - preview none. The node still executes and passes the images through, it just skips the expensive save-to-temp-and-display step.
• any positive number - preview exactly that many frames from the start of the batch, then stop.

The node saves each preview to ComfyUI's temp directory (that's what makes it show up in the UI), and it's marked as an output node so the workflow treats it as a terminal preview point. Importantly, it passes the images through on the IMAGE output - so you can drop it mid-pipeline to inspect a batch without breaking the flow to your save node. That pass-through is the reason it earns its place: it's a debug instrument that doesn't force a rewire.

Why you'd reach for it

Two situations. First, batch workflows where previewing all 32 frames grinds the UI - set Show_Images to 4 and you get a representative peek at a fraction of the cost. Second, mid-pipeline inspection: drop it after a VAE decode, check a couple of frames, and let the batch continue to a video-encode or save node. It also makes a handy "show what's about to be saved" checkpoint before a final output node.

Installing it

Part of ComfyUI-RvTools_v2 - Manager → search "ComfyUI-RvTools_v2", or:

cd ComfyUI/custom_nodes
git clone https://github.com/r-vage/ComfyUI-RvTools_v2
# restart ComfyUI

No extra dependencies - this is just ComfyUI's own preview machinery with a counter bolted on.

Gotchas

Setting Show_Images to 0 doesn't skip the node's execution entirely - it still runs and passes the tensor through, it just skips the preview save. That's usually what you want (fast pass-through), but if you need to fully disable it, mute the node instead. One subtlety: previews go to the temp folder, so they're not your final output - don't confuse what you see in the pane with what gets saved by your Save Image node. And the standing pack caveat: RvTools_v2 is unmaintained, superseded by ComfyUI_Eclipse, and the [RvTools] name suffix is the thing that trips up Manager on older shared workflows.