How is a whirl different from a plain rotation?

A plain rotation (like the PNG Rotator) spins the entire image by one fixed angle. A whirl instead applies a rotation angle that's strongest at the exact center and fades to zero at the edge of the whirl radius, producing a swirling, whirlpool-like warp rather than a uniform spin.

What does the strength control?

Strength (-720 to 720 degrees) sets the rotation angle applied at the very center of the whirl; the actual angle at any given pixel decays quadratically toward 0 as you move away from the center, out to the whirl radius.

What does the radius control?

Radius (as a percentage of the image's half-diagonal) sets how far from the center the whirl effect extends. Pixels beyond that radius are left completely unaffected.

Can I whirl in the opposite direction?

Yes. Use a negative strength value to whirl counter-clockwise instead of clockwise.

PNG Whirl Adder - Add a Swirl Distortion to an Image Online

Overview

Introduction

This tool adds a swirling whirlpool distortion around a PNG's center, entirely in your browser.

It works on a plain pixel buffer, so nothing you upload is sent to a server.

What Is PNG Whirl Adder?

A whirl (swirl) distortion tool that warps pixels around the image's center by a rotation angle that decays smoothly from the center outward, rather than a single uniform rotation angle applied to the whole image.

It builds on the same inverse-sampling technique the PNG Rotator uses, but with a radius-dependent angle instead of one fixed angle.

How PNG Whirl Adder Works

For every output pixel, the tool computes its distance from the image center and, if that distance is within the whirl radius, derives a local rotation angle that's strongest exactly at the center and fades quadratically to zero at the radius's edge.

It then works backward (inverse sampling) using that local angle to find the corresponding source pixel, the same technique `rotatePng` uses for a uniform rotation, just with a position-dependent angle instead of a constant one.

When To Use PNG Whirl Adder

Use it for a creative, eye-catching swirl effect on a photo or graphic, or to simulate a whirlpool/vortex look.

It works especially well centered on a focal point like a face, logo, or single object.

Often used alongside PNG Rotator, Glitch PNG Creator and PNG Zoomer.

Features

Advantages

Runs entirely client-side; nothing you upload leaves your device.
Independent strength and radius controls let you dial in anything from a subtle twist to a dramatic vortex.
Pixels outside the whirl radius are left completely untouched, keeping the rest of the image sharp.

Limitations

Sampling is nearest-neighbor, so strongly whirled areas can show some stair-stepping rather than perfectly smooth curves.
A whirl centered on an off-center subject won't automatically follow it; the effect is always centered on the image's geometric middle.

Examples

Gentle center twist

Input

A 400x400 PNG, strength 60, radius 60%

Output

A 400x400 PNG with a mild swirl near the center, edges unaffected

A moderate strength and radius produce a noticeable but not overwhelming twist near the middle.

Dramatic full-image whirlpool

Input

A 400x400 PNG, strength 300, radius 150%

Output

A 400x400 PNG that looks pulled into a swirling vortex across nearly the whole frame

A large radius extends the effect past the image's corners, and high strength makes the twist dramatic.

Best Practices & Notes

Best Practices

Center your subject in the source image before whirling for the most flattering result.
Start with a moderate strength (like 90-180) and increase gradually rather than jumping to extreme values.

Developer Notes

The pure whirl math lives in a lib function operating on a Uint8ClampedArray pixel buffer, computing a per-pixel angle as `strength * (1 - distance/radius)^2` and reusing the same inverse-rotation sampling formula `rotatePng` uses, just with that position-dependent angle substituted in for its single constant one.

PNG Whirl Adder Use Cases

Creating an eye-catching swirl effect for a poster or thumbnail
Simulating a whirlpool or vortex visual effect
Adding a playful distortion to an icon or avatar

Common Mistakes

Setting the radius too small and being surprised the effect barely shows.
Expecting the whirl to follow an off-center subject — it's always centered on the image's geometric middle.

Tips

Try a radius around 80-120% to have the whirl fade out gracefully near the image edges.
Combine with the corner rounder for a swirled circular badge-style graphic.

PNG Whirl Adder