Gamma Correct an Image
Brighten or darken image midtones without clipping black or white. Adjust overall or per-channel gamma, locally in your browser.
Gamma-correct image midtones
Gamma correction applies a power curve to image midtones. It is different from a flat brightness slider: pure black and pure white stay fixed, while the tones in between move. Use it to lift a dark photo without immediately clipping the highlights, darken washed-out midtones, or correct a subtle channel color cast.
A gamma value above 1 brightens midtones; a value below 1 darkens them. Leave
gamma_r, gamma_g and gamma_b at 1 for a neutral correction, or adjust one
channel to warm/cool the image. gamma_weight controls how strongly the gamma
curve applies near highlights: lower it when a strong brighten setting makes
bright areas look too hot.
Worked example
Upload a dim JPEG and choose the Brighten dark photo preset (gamma = 1.8,
all channel gammas at 1, gamma_weight = 1). Mid-gray pixels become much
brighter, while black and white remain anchored. If the brightest parts feel too
strong, try Protect highlights (gamma = 2.2, gamma_weight = 0.35) so the
curve fades near the top end. To fix a cool cast, set Red gamma to 1.25 and
Blue gamma to 0.85, then export as PNG.
Limits and edge cases
- Input images up to 8 MiB are processed locally in the browser with ffmpeg.
gamma,gamma_r,gamma_gandgamma_baccept0.1through10;1is no change.gamma_weightaccepts0through1.keeppreserves the input container. Choosingpng,jpgorwebpconverts the output; animated images are treated as stills when converted.- Gamma correction is not a full raw-photo exposure pipeline. It does not recover clipped highlights or shadows that are already pure white/black.
- The operation is RGB/video-filter based, so embedded color profiles and EXIF metadata are not preserved.
FAQ
What gamma value should I start with?
Try 1.6 to 2.0 for a dark photo and 0.5 to 0.8 for washed-out midtones.
1 is the identity. Small changes are usually best; strong values can make skin
or gradients look unnatural.
How is gamma different from brightness?
Brightness adds or subtracts from the whole image and can clip black or white quickly. Gamma bends the middle of the tone curve while keeping the endpoints fixed, so it is better for midtone-only adjustments.
What does gamma_weight do?
It fades the gamma correction near highlights. At 1, the full curve applies.
Lower values reduce the effect on bright pixels, which helps protect light skies,
paper, or reflections when you brighten a dark image.
Can I fix a color cast?
Yes, use gamma_r, gamma_g and gamma_b for per-channel midtone changes. For
example, raising red gamma and lowering blue gamma warms the image; doing the
opposite cools it.
Is my image uploaded?
No. The page runs ffmpeg in WebAssembly in your browser tab. The image file stays on your device.
Developer & Automation Access
Run it from the terminal
Same engine as this page, headless — via the gizza CLI:
gizza tool gamma-correct 'url=https://example.com/input' 'gamma=1.8' 'gamma_r=1' 'gamma_g=1' 'gamma_b=1' 'gamma_weight=1' 'format=keep'New to the CLI? Get gizza →
Open it by URL
Pre-fill and auto-run this tool with query parameters — the names match the API/CLI:
https://gizza.ai/tools/gamma-correct/?url=https://example.com/input&gamma=1.8&gamma_r=1&gamma_g=1&gamma_b=1&gamma_weight=1&format=keepMachine-readable descriptor: tool.json — title + parameters JSON Schema for agents.