Step-by-Step Comparer

The question every sampler tweaker eventually asks is whether steps 15–20 actually changed the image or just burned GPU time. StepStepComparer gives you a way to see the answer: feed it the sampler's STEP_IMAGES, pick step 5 on one slider and step 20 on the other, then drag the vertical divider across the frame to reveal exactly what changed between them.

It's the same viewer architecture as the pack's Player, aimed at a different job - not playback, but before/after forensics.

What it takes

One input, images (typed IMAGE), which in practice is the STEP_IMAGES output of StepByStepSampler. Like the Player it's an output node - no sockets out, it just renders.

How it works

The Python side base64-encodes the frames as JPEGs and ships them over ComfyUI's websocket; the bundled JS extension stacks two of the frames on top of each other and uses a CSS clip to slice the top one at the divider position. Two sliders choose which steps go on side A and side B, and the vertical bar is draggable. The diff itself is computed by your eyeballs, which is honestly the point - a PSNR number tells you the image stopped changing, and this shows you where it stopped changing.

Why you'd reach for it

Two real use cases. First, hunting your minimum viable step count: if the split view between step 12 and step 20 shows nothing but identical pixels, you just found 8 steps of wasted time (and the pack's auto_stop can automate exactly that decision). Second, debugging composition vs. refinement: early steps are where structure locks in, late steps only polish texture. A single split comparison shows you which phase your settings are operating in.

Install

Same pack, one install covers all three nodes - ComfyUI Manager (search "ComfyUI-StepByStep-Sampler") or:

cd ComfyUI/custom_nodes
git clone https://github.com/TakkunRed/ComfyUI-StepByStep-Sampler.git

then restart ComfyUI.

Gotchas

The same frontend caveats as the Player: it needs a live browser session, so after installing, restart ComfyUI and hard-refresh the tab or the widget stays blank. And one tip specific to this node - the sampler's show_overlay bakes the step label into the frames, which gets visually noisy in a split comparison. Turn show_overlay off on the sampler if you want clean A/B frames. You'll still know which step is which; the two sliders remember.