before_after_slider

Before/after comparison widget for Flutter with a draggable divider, zoom, pan, custom overlays, and label behavior control.

Perfect for image editing previews, map/style comparisons, redesign demos, and any side-by-side state comparison UI.

Features

• Compare two images with BeforeAfter
• Compare any two widgets with BeforeAfter
• Smooth drag gesture and full divider-line hit area
• Pinch-to-zoom and pan gestures
• Double-tap to reset zoom
• Custom overlay style (OverlayStyle) or fully custom overlay builder
• Custom labels (beforeLabelBuilder, afterLabelBuilder)
• fixedLabels mode to keep labels static during zoom/pan
• External ZoomController for programmatic control
• Controlled/uncontrolled progress modes

Platform Support

Android	iOS	Web	macOS	Windows	Linux
✅	✅	✅	✅	✅	✅

Installation

dependencies:
  before_after_slider: ^2.0.0

flutter pub get

Quick Start

import 'package:before_after_slider/before_after_slider.dart';

BeforeAfter(
  beforeChild: const Image(image: AssetImage('assets/before.jpg')),
  afterChild: const Image(image: AssetImage('assets/after.jpg')),
)

Usage

Image Comparison

BeforeAfter(
  beforeChild: const Image(
    image: AssetImage('assets/before.jpg'),
    fit: BoxFit.contain,
    alignment: Alignment.center,
  ),
  afterChild: const Image(
    image: AssetImage('assets/after.jpg'),
    fit: BoxFit.contain,
    alignment: Alignment.center,
  ),
  progress: 0.5,
  enableZoom: true,
  fixedLabels: true,
  overlayStyle: const OverlayStyle(
    dividerWidth: 2,
    thumbSize: 40,
  ),
  onProgressChanged: (value) {
    // 0.0 .. 1.0
  },
)

Widget Comparison

BeforeAfter(
  beforeChild: Container(color: const Color(0xFFDCEBFF)),
  afterChild: Container(color: const Color(0xFFFFECD8)),
  enableZoom: true,
  fixedLabels: true,
)

Zoom Controller

final controller = ZoomController();

BeforeAfter(
  beforeChild: const Image(image: AssetImage('assets/before.jpg')),
  afterChild: const Image(image: AssetImage('assets/after.jpg')),
  zoomController: controller,
);

// Programmatic reset:
controller.reset();

API At A Glance

Core Widgets

BeforeAfter supports:

• progress (controlled mode)
• onProgressChanged, onProgressStart, onProgressEnd
• enableProgressWithTouch
• enableZoom
• fixedLabels
• contentOrder
• overlayStyle
• beforeLabelBuilder, afterLabelBuilder
• overlay (custom builder)
• zoomController

fixedLabels Behavior

• fixedLabels: true (default)
  Labels stay in static screen positions while content zooms/pans.
• fixedLabels: false
  Labels transform together with compared content.

Migration From 1.x

2.0.0 contains a breaking API change.

• Removed: BeforeAfterImage
• Removed: BeforeAfterLayout
• Use: BeforeAfter(beforeChild: ..., afterChild: ...)

Before (1.x)

BeforeAfterImage(
  beforeImage: const AssetImage('assets/before.jpg'),
  afterImage: const AssetImage('assets/after.jpg'),
)

BeforeAfterLayout(
  beforeChild: Container(color: Colors.red),
  afterChild: Container(color: Colors.blue),
)

After (2.x)

BeforeAfter(
  beforeChild: const Image(image: AssetImage('assets/before.jpg')),
  afterChild: const Image(image: AssetImage('assets/after.jpg')),
)

BeforeAfter(
  beforeChild: Container(color: Colors.red),
  afterChild: Container(color: Colors.blue),
)

Example App

Interactive demo app is included in:

example/lib/main.dart

Contributing

Issues and pull requests are welcome:

• Repository: github.com/IgorShahin/before_after_slider
• Issues: github.com/IgorShahin/before_after_slider/issues

License

See LICENSE.