RC Channel Mixer

Channel Mixer is the adjustment layer everybody skips and every professional colorist secretly loves. It's the node you reach for when a warm cast won't go away, when a sky needs more drama, or when you want a black-and-white conversion that actually flatters the subject instead of averaging everything to gray. RC Channel Mixer brings the full Photoshop implementation into ComfyUI - all nine mixing coefficients plus monochrome mode - with the pack's usual bilingual tooltips holding your hand.

It's part of the RC Image Compositor pack. The concept is simple: each output channel (red, green, blue) becomes a weighted sum of the input channels. The effect is subtle when you nudge it and transformative when you lean on it.

How it works

The math is a 3×3 matrix. red_from_red, red_from_green, red_from_blue define how much of each input channel goes into the red output; the green and blue outputs follow the same pattern. Values are percentages, −200 to 200, defaulting to an identity matrix (red→red 100%, green→green 100%, blue→blue 100%) so the node starts as a no-op.

This gives you moves that are hard to do any other way:

• Kill a color cast by lowering the offending channel's contribution.
• Swap channels for that eerie IR look: put blue into red and red into blue.
• Build a custom monochrome mix - the readme mentions B&W filter presets modeled on classic red/orange/yellow/green/blue/infrared glass filters, which are the "why did you spend $400 on a filter" trick photographers have used forever.

The monochrome toggle flips it into grayscale mode, and per the tooltip it uses only the red channel's settings - so red_from_red/green/blue become your B&W mix coefficients. That's a specific, intentional design choice: adjust those three to shape the grayscale.

The inputs that matter

• image - input tensor.
• The nine *_from_* coefficients - this is the whole game. For a first project, only touch red_from_* with monochrome on.
• monochrome - on for B&W conversion, off for color work.

Output is a single IMAGE tensor.

How to install it

Ships with the RC Image Compositor pack:

cd ComfyUI/custom_nodes
git clone https://github.com/kj863257/ComfyUI_RC_Image_Compositor
cd ComfyUI_RC_Image_Compositor
pip install -r requirements.txt

Restart ComfyUI, or search "RC Image Compositor" in ComfyUI Manager. Dependencies: pillow, numpy, opencv-python, nothing exotic.

Common issues

The classic mistake is summing the coefficients well over 100% and wondering why highlights clip to white. Channel Mixer is not automatically normalized - you're responsible for the balance. If you push values aggressively, watch your whites.

For B&W work, a neutral mix (equal contributions summing to 100) is fine but boring; the whole point of a red filter, say, is dumping more red into the output and less blue and green, which darkens blue skies and brightens skin. If your "film noir" conversion comes out muddy, you're missing that imbalance on purpose.

And if your goal is just luminance or a single channel as a mask, don't fight it here - the pack's RC Channel Extractor does that directly with a dropdown.