Sharpen image
To sharpen an image is to draw edges and fine detail more strongly. Choose a photo, move the sliders, compare before and after and save it, all in your browser: the image is never uploaded. The method is the classic unsharp mask used in photo editors.
Source: Wikipedia – Unsharp masking. Updated: .
How it is calculated
In short: the tool strengthens the difference between each pixel and its blurred surroundings. At an edge the bright side gets a little brighter and the dark side a little darker, so the image looks sharper. This is the unsharp mask, the standard method in photo editing.
How it works
- Drop an image, choose one or paste it with Ctrl + V.
- Set amount and radius. The preview shows the original and the result side by side.
- For noise or skin tones raise the threshold so that smooth areas stay untouched.
- If needed adjust brightness and contrast, pick a format and click “Save image”.
The sliders
- Amount: how strongly edges are emphasised. 80–150% usually suits photos; more creates bright halos.
- Radius: how wide the edge zone is. Small values (0.5–1.5 px) for fine detail, larger ones for big images.
- Threshold: differences below this value stay unchanged, so image noise is not sharpened.
- Brightness and contrast: simple correction after sharpening.
Honest limits
- Sharpening cannot bring back detail that was never captured. A badly shaken or tiny image stays soft; only the edge impression improves.
- Too much amount causes bright rims around edges (halos) and emphasises noise.
- The preview radius is scaled to the image size so that it matches the saved result.
- Very large images are reduced to the browser limit; on iPhone and iPad that is 16.7 megapixels.
Privacy
The image is processed only in your browser and is not uploaded.
Frequently asked questions
How can I sharpen an image online?
Drop or choose the image, set amount and radius and click “Save image”. Everything runs in the browser and nothing is uploaded.
Which settings work well for photos?
A good start is amount 100%, radius 1 to 1.5 px and threshold 0 to 3. Very large images can take a slightly larger radius. Check the preview for bright halos along edges.
Can I really make a blurry image sharp?
Only to a degree. The unsharp mask raises contrast at edges, which looks sharper, but it cannot invent lost detail. Heavy blur or camera shake limits the result.
What does the threshold do?
Only differences above the threshold are strengthened. A higher value leaves noise and smooth areas such as sky or skin unchanged.
Is my image uploaded?
No. Sharpening runs entirely in your browser; the image never leaves your device.
Which format should I save in?
PNG is lossless, JPG gives smaller files for photos, WebP is a compromise. “Like original” keeps JPG for photos and PNG for graphics.
Sources and legal basis
- Wikipedia – Unsharp masking
- Wikipedia – Gaussian blur (box blur approximation)
- Ivan Kutskir – Fastest Gaussian blur (implemented in O(1) time)
- MDN – ImageData: pixel data of a canvas (RGBA, 8 bit)
- ITU-T T.81 / ISO/IEC 10918-1 – JPEG
- W3C – Portable Network Graphics (PNG) Specification
- Google for Developers – An image format for the Web (WebP)
- AOMedia – AV1 Image File Format (AVIF)
- MDN – Image file type and format guide
- MDN – HTMLCanvasElement.toBlob()
- Open-source licenses of the libraries used (MIT, LGPL-3.0)
As of: · Editorial policy
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