Flutter Magnifier Lens

A highly customizable magnifying glass widget for Flutter. It uses Fragment Shaders to provide realistic optical effects including spherical distortion, magnification, and chromatic aberration.

Features

Realistic Optical Effects: Adjustable magnification, spherical distortion, and chromatic aberration via high-performance Impeller/OpenGL custom shaders.
Dynamic Interaction: Effortlessly integrates with gesture detectors, allowing users to move and pinch-to-zoom the lens across the screen.
Highly Customizable: Easily modify lens radius, borders, and drop shadows to match your app's UI.
Image Overlays: Support for custom decorative PNG overlay layers on top of the lens disc.
High Performance: Built for Flutter 3.41+ using synchronous pixel decoding (decodeImageFromPixelsSync) and single-pass shader rendering.

Demo

Getting started

Add the package to your pubspec.yaml:

dependencies:
  flutter_magnifier_lens: ^1.0.3

Usage

To use the MagnifierLens, you must wrap the content you wish to magnify with a RepaintBoundary and assign it a GlobalKey. Pass that same key to the contentKey property of the MagnifierLens.

Here is a simple example that implements a draggable and pinch-to-zoom magnifier:

import 'package:flutter/material.dart';
import 'package:flutter_magnifier_lens/flutter_magnifier_lens.dart';

class MagnifierExample extends StatefulWidget {
  @override
  _MagnifierExampleState createState() => _MagnifierExampleState();
}

class _MagnifierExampleState extends State<MagnifierExample> {
  final GlobalKey _contentKey = GlobalKey();

  Offset _lensPosition = const Offset(200, 200);
  double _lensRadius = 100.0;
  double _baseLensRadius = 100.0;
  double _magnification = 1.5;

  @override
  Widget build(BuildContext context) {
    return GestureDetector(
      // Allow moving the lens and scaling it via pinch-to-zoom
      onScaleStart: (details) {
        _baseLensRadius = _lensRadius;
      },
      onScaleUpdate: (details) {
        setState(() {
          _lensPosition += details.focalPointDelta;
          if (details.scale != 1.0) {
            _lensRadius = (_baseLensRadius * details.scale).clamp(50.0, 300.0);
            _magnification = 1.0 + (_lensRadius / 200.0); // Adjust zoom dynamically
          }
        });
      },
      child: MagnifierLens(
        contentKey: _contentKey,
        lensPosition: _lensPosition,
        lensRadius: _lensRadius,
        distortion: 0.5,
        magnification: _magnification,
        aberration: 0.05,
        showBorder: true,
        borderColor: Colors.blueAccent,
        borderWidth: 3.0,
        showShadow: true,
        shadowColor: Colors.black45,
        shadowBlurRadius: 15.0,
        child: RepaintBoundary(
          key: _contentKey,
          child: Container(
            color: Colors.white,
            alignment: Alignment.center,
            child: Image.network(
              'https://flutter.github.io/assets-for-api-docs/assets/widgets/flamingos.jpg',
            ),
          ),
        ),
      ),
    );
  }
}

Properties

Property	Type	Default	Description
`child`	`Widget`	required	The widget hierarchy containing the content to be displayed and magnified.
`contentKey`	`GlobalKey`	required	A key attached to the RepaintBoundary inside the `child` representing the captured background.
`activated`	`bool`	`true`	Whether the lens effect is currently active and visible.
`lensPosition`	`Offset`	`Offset(200, 200)`	The screen coordinate representing the center of the magnifier.
`lensRadius`	`double`	`100.0`	The radius of the magnifying lens disc.
`distortion`	`double`	`0.5`	The amount of spherical distortion applied toward the edges.
`magnification`	`double`	`1.5`	The base zoom factor of the lens.
`aberration`	`double`	`0.05`	The strength of the RGB chromatic aberration split.
`showBorder`	`bool`	`true`	Whether to draw a border outline around the lens disc.
`borderColor`	`Color`	`Colors.white`	The color of the lens border.
`borderWidth`	`double`	`3.0`	The thickness of the lens border.
`showShadow`	`bool`	`true`	Drops an outer shadow beneath the lens.
`shadowColor`	`Color`	`Colors.black45`	Color of the lens shadow.
`shadowBlurRadius`	`double`	`15.0`	Outer blur radius of the shadow to give depth.
`overlayImage`	`ui.Image?`	`null`	A dynamic layer to draw on top of the lens, such as gloss or reflections.

Example

Check out the example directory for a complete example app that demonstrates all features.

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

License

This project is licensed under the MIT License - see the LICENSE file for details.