Flex Image Contrast ⚡🅡🅞🅣🅘

The plainest of RyanOnTheInside's image nodes, and honestly one of the more useful ones day to day - it's just contrast and brightness, but with the option to have either one driven by a reactive Feature instead of sitting fixed for a whole clip. Think a subtle contrast pump that tracks a kick drum, or a brightness lift that follows overall scene motion.

How it works

contrast (0–3, default 1) is a straight multiplier: 1 is unchanged, below 1 flattens the image toward gray, above 1 pushes lights and darks further apart. brightness (-1 to 1, default 0) shifts the whole image up or down. preserve_luminosity (on by default) keeps the image's overall perceived brightness roughly constant while contrast is being pushed around - without it, cranking contrast tends to visibly darken or brighten the average image as a side effect, which usually isn't what you want if contrast is the only thing you meant to change.

Any one of the three can be the modulation target: feature_param picks contrast, brightness, preserve_luminosity, or None for no modulation. Note that preserve_luminosity is a boolean under the hood, so if a feature is driving it, what actually happens is that feature crossing some effective threshold flips the setting rather than smoothly scaling it - this is one of the rare Flex parameters where "modulation" behaves like a toggle rather than a dial. feature_mode (relative/absolute) and feature_threshold work as they do across the rest of the pack, and strength scales overall pull.

Inputs and outputs that matter

• images - required.
• contrast and brightness - the two dials that matter; adjust these by hand first before adding feature modulation, so you know your baseline look.
• preserve_luminosity - leave it on unless you specifically want brightness to drift as a side effect of contrast changes.

Output is a single IMAGE.

How to install it

Via ComfyUI Manager, search "RyanOnTheInside." Manually:

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

then restart. No model files, no heavy dependency specific to this node - it's a basic tensor operation.

Common issues & troubleshooting

Image gets noticeably darker or brighter just from raising contrast. That's preserve_luminosity being off. Turn it back on if you want contrast and brightness to behave as independent controls rather than bleeding into each other.

Feature-driven preserve_luminosity feels like it "snaps" instead of ramping smoothly. That's expected - it's a boolean setting, so a feature driving it is really just flipping it on or off past some point in its range, not gradually blending between the two states. If you want a smooth reactive brightness effect, drive brightness or contrast with the feature instead and leave preserve_luminosity fixed.

Contrast pushed high looks blown out or crushed rather than punchy. contrast can go up to 3, which is an aggressive multiplier - most usable looks sit well under 1.5 unless you're deliberately going for a harsh, high-contrast style. Push it gradually and watch your highlights/shadows for clipping.