What's the difference between a positive and negative strength value?

A positive strength (up to 90) creates a convex bulge, as if the image were wrapped around the outside of a sphere or seen through a fisheye lens; a negative strength (down to -90) creates a concave pinch, as if the center were sucked inward.

Why is the effect circular instead of covering the whole rectangle?

The distortion is computed relative to the image's inscribed circle (centered, radius equal to half the shorter side), so it stays contained to a circular region; pixels outside that circle are copied through unchanged.

Does this affect image quality?

Yes, slightly. The tool uses nearest-neighbor sampling for the remapped pixels, so very strong bulge or pinch settings can show minor pixelation or stretching artifacts near the center or edge of the affected circle.

What strength value gives a mild effect?

Values in the 10-30 range give a gentle, barely-there bulge, while values above 60 produce a dramatic, exaggerated fisheye look.

PNG Spherical Effect Adder - Add a Fisheye Bulge or Pinch Online

Overview

Introduction

This tool adds a spherical bulge or pinch distortion around a PNG's center, simulating a fisheye lens or a sphere-warp effect entirely in your browser.

A single strength value controls both the direction (bulge or pinch) and the intensity of the distortion.

What Is PNG Spherical Effect Adder?

A client-side effect that remaps pixel positions within the image's inscribed circle using a power-law radial transform, similar to how a fisheye lens or a rendered sphere distorts a flat image.

Positive strength values bulge the center outward; negative values pinch it inward. Pixels outside the circle are left untouched.

How PNG Spherical Effect Adder Works

For every output pixel inside the inscribed circle, the tool computes its normalized radius (0 at the center, 1 at the circle's edge), remaps that radius to `radius ^ (1 - strength/100)`, and then samples the source image at the new radius along the same angle — the same inverse-sampling approach used by the rotator tool, just with a radial power-law instead of an angular offset.

A positive strength makes the exponent less than 1, which pulls source pixels from closer to the center outward for a convex bulge; a negative strength makes the exponent greater than 1, pulling pixels inward for a pinch.

When To Use PNG Spherical Effect Adder

Use it to create a fun, exaggerated fisheye-lens look for a photo, avatar, or thumbnail.

It's also useful for simulating how a flat image or logo would look wrapped around a sphere or globe.

Often used alongside PNG Mobius Transform Applier, PNG Kaleidoscope Effect Adder and PNG Rotator.

Features

Advantages

Runs entirely client-side; the uploaded image never leaves your device.
One control handles both bulge and pinch directions via positive and negative values.
The effect stays contained to a circular region, leaving the rest of the image untouched.

Limitations

Nearest-neighbor sampling can show minor pixelation at strong bulge or pinch settings.
On non-square images, the circular effect region only covers up to the shorter dimension, leaving visible untouched strips on the longer side.

Examples

Mild fisheye bulge on a portrait

Input

A 600x600 PNG portrait, strength = 30

Output

A 600x600 PNG with a gentle, rounded bulge centered on the face

Moderate positive strength gives a noticeable but natural-looking lens distortion.

Strong pinch effect

Input

A 600x600 PNG texture, strength = -60

Output

A 600x600 PNG with the center pulled sharply inward, like a black hole effect

A large negative strength value produces a dramatic concave pinch toward the center.

Best Practices & Notes

Best Practices

Crop to a square first if you want the circular distortion to reach all four edges evenly.
Start with strength values under 40 for a natural-looking lens effect before trying more extreme settings.

Developer Notes

The lib function operates on a plain Uint8ClampedArray PixelBuffer with no DOM dependency: it computes exponent = 1 - strength/100, and for each pixel inside the inscribed circle remaps normalizedDist via Math.pow(normalizedDist, exponent) before inverse-sampling the source at the rescaled radius and unchanged angle; pixels outside the circle pass through unchanged.

PNG Spherical Effect Adder Use Cases

Creating a fisheye-lens effect for a profile photo or thumbnail
Simulating how a flat texture wraps around a sphere or globe
Making a playful 'black hole' pinch effect for a meme or graphic

Common Mistakes

Expecting the effect to cover the full rectangular image — it's contained to the inscribed circle based on the shorter dimension.
Using an extreme strength value (near ±90) and being surprised by visible pixelation near the center.

Tips

Combine with the Mobius transform tool for more creative, non-radially-symmetric distortions.
Try small negative values (-10 to -20) for a subtle 'looking through a bottle' pinch effect.

PNG Spherical Effect Adder