ImageEffectsNegative

A color negative is one of those transformations you rarely need and then suddenly need in five different places - inverting a look, checking a mask's contrast, faking a film-reversal aesthetic, or pre-inverting an image before some pipeline step that expects it. ImageEffectsNegative from the Allor plugin is the zero-config version: feed it an image, get the inverted image back. No sliders, no modes, no way to get it wrong.

How it works

The math is exactly as simple as it sounds: each RGB channel is flipped with 1.0 - channel, which is the standard inversion on ComfyUI's 0-to-1 image tensors. What's worth knowing is what it doesn't touch - it operates only on the first three channels, so the alpha channel of a transparent image passes straight through untouched. That's a deliberate design choice across the Allor pack (the plugin's whole identity is transparency-and-batch-safe image ops), and it means you can invert the pixels of a cutout without wrecking the mask that keeps your subject composited correctly.

It's a pure tensor operation, so it runs on the whole batch at once and costs basically nothing. Drop it in the middle of a chain wherever an inversion belongs; it won't be your bottleneck.

Inputs and output

• images - an IMAGE or a batch of IMAGEs. The only input.
• Output: an IMAGE, same dimensions and (for RGBA inputs) same alpha as the input.

If you invert twice you get your original back, which makes it handy as a temporary step while you're debugging a workflow - insert it, inspect, remove it.

Installing it

It's part of the Allor pack (~90 nodes installed together):

cd ComfyUI/custom_nodes
git clone https://github.com/Nourepide/ComfyUI-Allor

Restart ComfyUI, or install via ComfyUI Manager by searching for Allor Plugin. First launch installs the pack's requirements.txt (rembg, onnx) and creates a config.json - slow the first time, then done. This node needs no models.

Gotchas

• It inverts colors, not luminance. Dark scenes come out bright, which is usually what you want from a negative but occasionally surprising if you only glanced at a thumbnail.
• Alpha is preserved - that's a feature, but if you genuinely want the alpha inverted too (weird but possible), you'll need a separate mask-invert node.
• Remember the pack's standing update gotcha: the repo was rebased to shrink history, so old clones can hit git pull errors. Clean re-clone fixes it.

Pair it with ImageEffectsGrayscale for a full B&W-negative treatment in two nodes.