How to use Image Sharpness Adjustment

Choose a JPEG, PNG or WebP within the stated image limits.
Start with a modest strength and choose the edge threshold.
Run the adjustment and compare the original at left with the result at right.
Check fine details and halos before saving the sharpened PNG.

Example: Image Sharpness Adjustment

A local worked example using the inputs and settings below for image sharpness adjustment.

You add

Image: ["sample.png (348 bytes)"] Sharpness strength: "0.8" Edge threshold: "5"

You get

Adjusted sharpness for sample.png. sample-sharpened.png (80 × 60 pixels) sample-sharpness-comparison.png (160 × 60 pixels)

Options

Strength: Strength adjusts edge contrast in decoded pixels. A stronger value can add halos without recovering detail.
Threshold: Threshold controls which differences receive the adjustment. Inspect small text and noise before accepting the sharpened copy.

Supported inputs and limits

File sizeOne image up to 64 MiB

Working pixels24 megapixels

FormatsJPEG, PNG and WebP within decoder limits

One JPEG, PNG or WebP up to 64 MiB, 24 megapixels and 10,000 pixels on either side. Strength is 0–2; threshold is a whole value from 0–100. The kernel compares a channel with its four adjacent pixels; borders and alpha stay unchanged. Output is PNG at input dimensions, with a separate comparison limited to 400 pixels per panel in width. Canvas decoding, colour conversion and re-encoding may change source pixels or metadata. This is edge contrast adjustment, not detail recovery.

Where your input is processed

This tool processes your input in this browser. Your text and files are not uploaded to UseFreeTools. Check this tool's limits for anything it may save on your device.

Inspect at the size you will use

A preview can make an edge look stronger while hiding artifacts that appear at full size. Open the exported PNG at the intended display or print scale. Keep the original when you want to try another strength, because repeated sharpening can accumulate unwanted contrast.

Questions about Image Sharpness Adjustment

Can sharpening recover missing detail?

It increases contrast around supported pixel differences. It does not reconstruct information that was lost to motion blur, focus or compression.

What causes bright or dark halos?

Strong edge contrast can overshoot neighbouring colours. Lower the strength and inspect text, hair and other high-contrast boundaries.

What does the threshold change?

It limits adjustments to channel differences above the selected value. A larger threshold can leave smaller differences unchanged, but it is not a noise-removal model.

Why is a comparison image smaller?

The side-by-side export is a bounded preview. The separate sharpened PNG retains the supported input dimensions; use that file to check the complete output.

Project manager: Tony Hines · Content updated 4 October 2026 · Report a problem