Channel Operations

Channel Operations is the node you reach for when a texture pipeline wants a map you don't have. Need a quick height map? Take the red channel, set blue and green to zero, done. Need an inverted mask? Invert one channel instead of running a whole Color Invert node. It's per-channel manipulation with zero cleverness - and that's exactly why it's handy.

How it works

You pick an operation per channel (red, green, blue) and the node applies it. The options:

• Passthrough - leave the channel alone.
• Normalize (0-1) - stretch that channel to use the full 0–1 range (auto-levels, per channel).
• Invert - 1 - value, flips black↔white.
• Set to 0 / 0.5 / 1 - force the channel to a fixed value.

Everything runs in tensor math, so batches are fine and it's effectively free. Output is a single IMAGE with the same size and format as the input.

The inputs that matter

Only required inputs, all enums:

• image - whatever you're processing.
• red_channel, green_channel, blue_channel - each defaults to Passthrough, so a common pattern is "set two to 0, leave one" to isolate a single channel.

What people actually use it for

In the game-texture context this pack lives in, the classic moves are:

• Channel extraction - set two channels to 0 and you've pulled a single channel out as a grayscale map (roughness from a packed map, for example).
• Stamping a map you don't have - a uniform-value channel can stand in for a flat roughness or a neutral mask.
• Per-channel normalize - when one channel is crushed into a small value range, stretching just that channel often beats global level adjustments.

Install

It ships in ComfyUI-Leputen-Utils:

cd ComfyUI/custom_nodes
git clone https://github.com/lilquail/ComfyUI-Leputen-Utils

Restart ComfyUI and the node appears under Leputen-Utils → Image. The pack's deps (scipy, opencv-python, onnxruntime, imageio) install automatically on first launch.

Gotchas

• Normalize is per-channel, not per-image. If you normalize R, G, and B independently on a color image, you'll shift the hue - fine for masks and maps, surprising for albedo. Set two channels to Normalize on a color image and you get a color cast you didn't ask for.
• This doesn't touch alpha. The node only has R/G/B inputs. If you need to operate on the alpha channel you'll want a dedicated mask/matte node.

That's it. It's a small utility, not a hero node - but in a batch pipeline churning out PBR sets, "isolate this channel, stamp that one" saves a surprising amount of graph clutter.