Image / Detail
Sharpen Image with an Unsharp Mask
Bring out edges in a photograph with adjustable sharpening. Compare before and after as you change amount, radius and threshold, then save a full-resolution PNG.
Sharpen Image with an Unsharp Mask: Adds a scaled difference between the original image and a softened copy. Amount sets the strength, radius sets the neighbourhood, and threshold leaves smaller channel differences alone. Alpha is preserved, and invisible colours are excluded from the blur. Runs 100% locally in your browser with zero server file uploads.
- Category
- Image tools
- Runs
- In your browser
- Cost
- Free · no sign-up
- Availability
- Ready to use
Runs entirely in your browser
Unsharp masking
The operation is original + amount × (original − blurred). Radius controls the extent of the blur, and threshold limits which differences receive sharpening. GIMP explains the principle and its controls: https://docs.gimp.org/3.0/en/gimp-filter-unsharp-mask.html . This tool uses two box-blur passes per axis as a Gaussian approximation, so its radius is not an exact match for other editors.
Checking the result
Start with a modest amount, raise the threshold for noisy photographs, and inspect high-contrast borders for bright or dark halos. Export as PNG to avoid another lossy encoding step. Sharpen after choosing final dimensions.
How to use it
- Choose a JPG, PNG or WebP image.
- Adjust amount, radius and threshold while comparing the live preview.
- Download a full-size PNG and check fine detail at its original scale.
Privacy & limitations
The image stays in your browser. Files are limited to 30 MB and 20 million pixels. Metadata is not copied to the output.
Related tools
Frequently asked questions
Can sharpening fix a badly blurred photo?
It increases edge contrast but cannot reconstruct missing detail. Strong settings can exaggerate noise and create halos.
Why does the export look different at full size?
The preview is reduced to a maximum of 600 pixels per side and approximates the radius. The export applies the chosen radius to the original pixels.
What does threshold measure?
It is the minimum absolute difference between an original colour channel and its blurred value on a 0–255 scale. A higher value leaves more small differences unchanged.
Free tool · runs in your browser · no account required