Improve the contrast of an image locally and automatically - the tonal range is stretched to the full span. No upload.
Running locally on your device ...
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Your files never left your device
No. Everything runs in your browser - your file never leaves your device. How this is verifiable
Auto contrast automatically stretches the tonal range of an image to the full span: the darkest existing tone becomes black, the brightest white, and everything in between is stretched evenly. Flat, low-contrast shots look crisper afterwards without you setting any slider.
It suits scans, hazy landscapes, underexposed snapshots, or any image that does not use the full black-to-white span. The stretch is applied equally to all colour channels, so the colour impression (hue) is preserved and only the contrast rises. The output keeps your original format and dimensions.
Everything runs entirely locally in your browser on a canvas (no upload, even offline) - your image never leaves your device. The darkest and brightest luminance are found, giving a linear stretch. An already flat image (all pixels equally bright) is left unchanged. Animated images are flattened to a single frame.
| Input formats | JPG, JPEG, PNG, WEBP |
|---|---|
| Output format | JPG |
| Batch processing | Yes |
| Processing | Locally in your browser (JavaScript) |
| File upload | None |
Limitations: Linearly stretches the tonal range so the darkest luminance maps to 0 and the brightest to 255; the same stretch hits all channels (hue is kept). A flat image (min equals max) is left unchanged. No slider. The original format and dimensions are preserved (PNG keeps transparency; JPEG flattens onto white). Animated inputs are reduced to a single frame.
No. The auto contrast runs entirely locally in the browser on a canvas - even offline. Your image never leaves your device.
The stretch is applied equally to all channels, so the hue is largely preserved; mostly the contrast increases.
No. The full tonal range is derived automatically from the image; there is deliberately no slider.
Yes. A PNG stays a PNG (with transparency), a JPEG stays a JPEG, and the dimensions are unchanged.