sharpen · convolution · png · local

Sharpen images with a 3x3 kernel

Classic sharpening kernel blended at adjustable strength. Great for rescuing slightly soft photos. Runs locally.

Image Sharpener
Source
—
no file
Strength
0.50
blend
Output
—
png
Status
idle
live
Strength:0.50
input · image

image/* · runs locally · nothing uploaded

output · preview
Original
—
Sharpened
—
Quick Start

How it works

Pick an image, tune the options, then download the result. Everything runs in your browser.

  1. 01

    Pick an image

    Drop or select any image.

    Files stay in memory as an HTMLImageElement — the original bytes are never uploaded, and EXIF metadata is preserved until you explicitly transform it.

    uploadcanvaslocaldecode
    input · bytesimage · loaded
    source.jpg
    loaded · decodedcanvas · ready
  2. 02

    Apply 3x3 kernel

    Each pixel is replaced by the convolution of its 3x3 neighbourhood with a Laplacian-like kernel.

    Encoder quality is exposed where the format supports it — JPEG and WebP get a 0–1 quality slider; PNG is lossless. Options re-render the canvas immediately.

    kerneloptionslive previewencoderquality
    kernel · tunable5/-1 · live
    [ 0 -1  0 ]
    [-1  5 -1 ]
    [ 0 -1  0 ]
    options applied · liveencoder · live
  3. 03

    Blend by strength

    Linearly mix the sharpened result back against the original.

    Pixel work runs on the Canvas 2D context — drawImage resamples with the browser’s bilinear filter and getImageData/putImageData back per-pixel passes.

    blendrenderCanvas 2Dpreviewpx-perfect
    strength · resampled0.50 · px-perfect
    out = orig + (sharp - orig) * 0.50
    preview · livepx-perfect
  4. 04

    Download PNG

    Save the sharpened image.

    Downloads ship via a hidden anchor with an object URL — no server round-trip, and the file on disk is untouched. The output filename inherits a sensible suffix.

    exportdownloadblobclient-sideobject URL
    ok · blobready · saved
    sharp.png
    shipped · ready to shipsuccess
Pro tips

Browser-only image work that scales

Convert with quality control

JPEG/WebP let you pick a 0–1 quality. Default 0.92 is a good compromise of size and visible quality.

PNG isn’t free

Use PNG only for transparency or sharp edges. For photos, WebP is smaller at the same perceived quality.

Strip EXIF for privacy

Photo EXIF often contains GPS, camera model, and timestamps. Strip before sharing public uploads.

Watch the colour profile

Convert to sRGB before web export. Wide-gamut images render oversaturated in non-managed browsers.

AVIF when it’s available

AVIF beats WebP on size at the same quality. Detect support via <picture> with fallbacks.

Lazy-load below the fold

Add loading="lazy" on <img>. The browser handles scheduling — no IntersectionObserver needed.

Use Cases

When to use this tool

Common workflows it speeds up.

Rescue soft photos

Tighten slightly out-of-focus shots. Decoded into a Canvas 2D context — original bytes never leave the tab, so you can process customer-uploaded photos, internal screenshots, or sensitive diagrams without privacy concerns.

px-perfect

Web thumbnails

Counter blur from JPEG re-encode. Encoders expose quality 0–1 where the format supports it (JPEG, WebP); PNG and AVIF stay perceptually lossless. Pick 0.85 for web, 0.95 for archival, 0.7 for thumbnails.

quality-tunable

Detail-heavy art

Bring out fine lines in illustrations. Pair with the EXIF Stripper before sharing user-uploaded photos publicly. Camera serial numbers, GPS coordinates, and timestamps often hide in image metadata and leak more than the picture itself.

format-aware

OCR prep

Sharpen scanned text before OCR. Output preserves colour profile (sRGB) so it renders consistently across browsers, monitors, and print pipelines. Wide-gamut workflows can opt into Display P3 for modern Apple devices.

EXIF-safe

Old scans

Restore edges in fading photo scans. Re-runs only on option changes, never on window resize, so the canvas stays responsive on large images. drawImage uses the browser's bilinear filter for fast resampling.

client-side

Compression rebound

Counteract slight compression softening. Downloads as .png, .jpg, .webp, or .avif with the correct MIME so editors apply native handling on save. The filename inherits a sensible suffix derived from the input.

compression-ready
FAQ

Frequently asked questions

No — sharpening can enhance existing edges but cannot recover information destroyed by motion or out-of-focus blur.
[[0,-1,0],[-1,5,-1],[0,-1,0]] — a classic Laplacian-of-Gaussian approximation.
Sharpening amplifies the difference between neighbours — fine noise gets enhanced too.
Yes — the alpha channel is left untouched.
No. Everything runs locally in your browser.
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