✨ Reflection Extractor

When a metal object comes out of a diffusion model, the reflections are usually flat - the model knows metal should be shiny but renders the highlights soft and muddy, so the material reads as plastic. Professional compositors fix this by layering a separate specular highlight pass over the render using Photoshop's Screen blend mode: put the dark parts of the highlight pass on black, blend with Screen, and the bright reflections brighten the image without ever darkening it.

✨ Reflection Extractor is the tool that builds that pass in ComfyUI. It takes your image and produces a specular highlight channel on a black background - precisely the format Screen compositing wants. The author's own description says the intended workflow: extract the channel here, then blend it in "in PS with Screen mode" to enhance the metallic reflection feel. You can do the same blend inside ComfyUI with this pack's Image Composite set to Screen mode - it's a complete two-node metal-polish chain.

What you control

• 强度 (strength, 0–3, default 1) - how strongly highlights are amplified in the output channel. Push past 1 and the reflections get hotter than the source, which is often exactly what a flat render needs.
• 对比度 (contrast, 1–10, default 4) - shapes the response curve between "everything is mid-gray" and "only the brightest pixels survive." Low contrast keeps a broad soft sheen; high contrast isolates the hard specular glints.
• 遮罩 (mask, optional, type *) - a mask to limit which region of the image is processed. Handy for only pulling highlights from, say, the car body and leaving the sky untouched.

Output is a single 镜面高光通道 (mirror highlight channel) of type IMAGE. Because it's black-backed and grayscale-ish, it previews as exactly the kind of pass you'd stack in a compositor.

Where it fits

Best on renders where you want to add material realism: metals, car paint, wet surfaces, glass. The chain is: generate → extract highlights → composite with Screen at a strength you like. And because Screen mode can only brighten, you can apply it over the same image or over a different background - which makes it genuinely useful for compositing a subject onto a new scene, where matching the lighting is half the battle.

Installing it

Part of the Louis Use pack:

cd ComfyUI/custom_nodes
git clone https://github.com/LouisLU1997/ComfyUI-louis-use Louis_use

Or "Louis Use" in ComfyUI Manager, then restart. No extra dependencies - the extraction is plain pixel math on the tensor.

The honest caveat

This is a pixel-level tool, not a lighting model. It can't invent a reflection that isn't in the image - if the render has no highlight, the output channel is black. What it does well is separate the brights from everything else and let you re-introduce them at the strength you want, which fixes the flat-metal problem in most cases. If the source genuinely lacks speculars, you'd want a different fix (relight or inpaint); for everything else, this is the compositor's extract-reflections node, minus the Photoshop subscription.