Image Sharpener
Apply a sharpening filter to bring out edges and detail in a soft or slightly out-of-focus photo, with a strength slider and live preview before downloading. Processed entirely in your browser.
Your image is processed on your device via Canvas and is never uploaded to our servers.
Drag an image here or choose one
JPG, PNG, or WebP
What this tool does
Increases an image's detail by an amount you control with a slider, by accentuating the difference between each pixel and its neighbours.
When to use it
- A photo looks slightly soft because of camera focus or because it was scaled down.
- A scan has lost some of its crispness.
- An image will be displayed small and you want its detail to read more clearly.
How to use it
- Drag an image onto the drop area or choose one — a single image at a time.
- Move the "Sharpen amount" slider and watch its effect.
- Click "Download image".
A practical example
Input
A photo scaled down from 4000 pixels to 1200, which left the edges soft.
Output
The same photo with crisper edges and more legible detail, at a moderate sharpen amount.
Overdoing it produces white halos along edges and amplifies noise — less is usually more.
Limitations
- Sharpening cannot recover detail that is not there; it accentuates what exists, so an out-of-focus photo stays out of focus.
- Pushing it too far creates halos around edges and exaggerates noise in dark areas.
- Images above roughly six million pixels are rejected with a clear message, because the filter visits every pixel together with its neighbours and would freeze the page on a huge image.
- One image at a time.
Privacy and processing
Processing happens inside your browser through the canvas and the image is never uploaded.
Technical notes
- The 3×3 convolution filter is written with no external dependency and is covered by unit tests that run in Node.
- The slider blends the sharpen kernel with a neutral one by the proportion you choose, which is what makes the intensity smooth rather than a single jump.