Dart - How to determine the width and height of an image in Flutter?

In Flutter, you can determine the width and height of an image in several ways, depending on whether the image is an asset, network image, or file. Below are methods to determine the dimensions of images in different scenarios:

1. Determining Image Dimensions from Asset

For assets, you need to load the image into memory and then use its Image class to get its dimensions. Here's how you can do it:

Example Code

import 'package:flutter/material.dart'; import 'package:flutter/services.dart' show rootBundle; import 'dart:ui' as ui; void main() { runApp(MyApp()); } class MyApp extends StatelessWidget { @override Widget build(BuildContext context) { return MaterialApp( home: ImageSizeExample(), ); } } class ImageSizeExample extends StatefulWidget { @override _ImageSizeExampleState createState() => _ImageSizeExampleState(); } class _ImageSizeExampleState extends State<ImageSizeExample> { Future<Size> _getImageSize() async { final ByteData data = await rootBundle.load('assets/your_image.png'); // Replace with your image asset path final Uint8List bytes = data.buffer.asUint8List(); final ui.Codec codec = await ui.instantiateImageCodec(bytes); final ui.FrameInfo frameInfo = await codec.getNextFrame(); final ui.Image image = frameInfo.image; return Size(image.width.toDouble(), image.height.toDouble()); } @override Widget build(BuildContext context) { return Scaffold( appBar: AppBar(title: Text('Image Size Example')), body: Center( child: FutureBuilder<Size>( future: _getImageSize(), builder: (context, snapshot) { if (snapshot.connectionState == ConnectionState.waiting) { return CircularProgressIndicator(); } else if (snapshot.hasError) { return Text('Error: ${snapshot.error}'); } else { final size = snapshot.data; return Text('Width: ${size?.width}, Height: ${size?.height}'); } }, ), ), ); } } 

2. Determining Image Dimensions from Network

For network images, you can use the Image class and its ImageStream to obtain the size.

Example Code

import 'package:flutter/material.dart'; void main() { runApp(MyApp()); } class MyApp extends StatelessWidget { @override Widget build(BuildContext context) { return MaterialApp( home: ImageSizeExample(), ); } } class ImageSizeExample extends StatefulWidget { @override _ImageSizeExampleState createState() => _ImageSizeExampleState(); } class _ImageSizeExampleState extends State<ImageSizeExample> { Future<Size> _getNetworkImageSize(String url) async { final Image image = Image.network(url); final Completer<ImageInfo> completer = Completer<ImageInfo>(); final ImageStream stream = image.image.resolve(ImageConfiguration.empty); final listener = ImageStreamListener((ImageInfo info, bool syncCall) { completer.complete(info); }); stream.addListener(listener); final ImageInfo imageInfo = await completer.future; final ui.Image img = imageInfo.image; return Size(img.width.toDouble(), img.height.toDouble()); } @override Widget build(BuildContext context) { return Scaffold( appBar: AppBar(title: Text('Image Size Example')), body: Center( child: FutureBuilder<Size>( future: _getNetworkImageSize('https://example.com/your_image.png'), // Replace with your image URL builder: (context, snapshot) { if (snapshot.connectionState == ConnectionState.waiting) { return CircularProgressIndicator(); } else if (snapshot.hasError) { return Text('Error: ${snapshot.error}'); } else { final size = snapshot.data; return Text('Width: ${size?.width}, Height: ${size?.height}'); } }, ), ), ); } } 

3. Determining Image Dimensions from File

For images stored in files, you can use the Image class in a similar way to the network image method.

Example Code

import 'package:flutter/material.dart'; import 'package:image/image.dart' as img; // Import image package void main() { runApp(MyApp()); } class MyApp extends StatelessWidget { @override Widget build(BuildContext context) { return MaterialApp( home: ImageSizeExample(), ); } } class ImageSizeExample extends StatefulWidget { @override _ImageSizeExampleState createState() => _ImageSizeExampleState(); } class _ImageSizeExampleState extends State<ImageSizeExample> { Future<Size> _getImageSizeFromFile(String filePath) async { final data = await File(filePath).readAsBytes(); final image = img.decodeImage(data); return Size(image!.width.toDouble(), image.height.toDouble()); } @override Widget build(BuildContext context) { return Scaffold( appBar: AppBar(title: Text('Image Size Example')), body: Center( child: FutureBuilder<Size>( future: _getImageSizeFromFile('/path/to/your_image.png'), // Replace with your image file path builder: (context, snapshot) { if (snapshot.connectionState == ConnectionState.waiting) { return CircularProgressIndicator(); } else if (snapshot.hasError) { return Text('Error: ${snapshot.error}'); } else { final size = snapshot.data; return Text('Width: ${size?.width}, Height: ${size?.height}'); } }, ), ), ); } } 

Explanation

• Image.asset: Loads an asset image and uses ui.instantiateImageCodec to get its dimensions.

• Image.network: Uses ImageStream to listen for the image loading completion and get its dimensions.

• Image.file: Uses the image package to decode the image and obtain its dimensions.

• FutureBuilder: Used to asynchronously load and display the image dimensions.

Dependencies

For file image operations, you might need to add the image package to your pubspec.yaml:

dependencies: flutter: sdk: flutter image: ^3.0.1 

By using these methods, you can effectively determine the width and height of images in different scenarios in Flutter.

Examples

1. Dart Flutter get image size after loading

   Description: Retrieve the dimensions of an image after it has been fully loaded in Flutter.

   Code:

   import 'package:flutter/material.dart'; import 'package:flutter/services.dart'; import 'dart:ui' as ui; class ImageSizeDemo extends StatefulWidget { @override _ImageSizeDemoState createState() => _ImageSizeDemoState(); } class _ImageSizeDemoState extends State<ImageSizeDemo> { ui.Image? _image; @override void initState() { super.initState(); _loadImage(); } Future<void> _loadImage() async { final ByteData data = await rootBundle.load('assets/your_image.png'); final Uint8List bytes = data.buffer.asUint8List(); final ui.Codec codec = await ui.instantiateImageCodec(bytes); final ui.FrameInfo frameInfo = await codec.getNextFrame(); setState(() { _image = frameInfo.image; }); } @override Widget build(BuildContext context) { return Scaffold( appBar: AppBar(title: Text('Image Size Demo')), body: Center( child: _image == null ? CircularProgressIndicator() : Text('Width: ${_image!.width}, Height: ${_image!.height}'), ), ); } } 

2. Flutter determine image dimensions using ImageProvider

   Description: Get image dimensions by loading the image through an ImageProvider.

   Code:

   import 'package:flutter/material.dart'; import 'package:flutter/services.dart'; import 'dart:ui' as ui; class ImageProviderSizeDemo extends StatefulWidget { @override _ImageProviderSizeDemoState createState() => _ImageProviderSizeDemoState(); } class _ImageProviderSizeDemoState extends State<ImageProviderSizeDemo> { Size? _imageSize; @override void initState() { super.initState(); _getImageSize(); } Future<void> _getImageSize() async { final image = AssetImage('assets/your_image.png'); final ImageStream stream = image.resolve(ImageConfiguration.empty); final ImageInfo info = await stream.first; setState(() { _imageSize = Size(info.image.width.toDouble(), info.image.height.toDouble()); }); } @override Widget build(BuildContext context) { return Scaffold( appBar: AppBar(title: Text('Image Provider Size Demo')), body: Center( child: _imageSize == null ? CircularProgressIndicator() : Text('Width: ${_imageSize!.width}, Height: ${_imageSize!.height}'), ), ); } } 

3. Flutter get image size using Image widget

   Description: Determine the dimensions of an image widget using Image widget properties.

   Code:

   import 'package:flutter/material.dart'; class ImageWidgetSizeDemo extends StatefulWidget { @override _ImageWidgetSizeDemoState createState() => _ImageWidgetSizeDemoState(); } class _ImageWidgetSizeDemoState extends State<ImageWidgetSizeDemo> { @override Widget build(BuildContext context) { return Scaffold( appBar: AppBar(title: Text('Image Widget Size Demo')), body: LayoutBuilder( builder: (context, constraints) { return Center( child: Container( width: 200, // Fixed width height: 200, // Fixed height child: Image.asset( 'assets/your_image.png', fit: BoxFit.cover, ), ), ); }, ), ); } } 

4. Dart Flutter obtain image size from network URL

   Description: Get dimensions of an image loaded from a network URL.

   Code:

   import 'package:flutter/material.dart'; import 'package:http/http.dart' as http; import 'dart:ui' as ui; import 'dart:typed_data'; class NetworkImageSizeDemo extends StatefulWidget { @override _NetworkImageSizeDemoState createState() => _NetworkImageSizeDemoState(); } class _NetworkImageSizeDemoState extends State<NetworkImageSizeDemo> { Size? _imageSize; @override void initState() { super.initState(); _getImageSize(); } Future<void> _getImageSize() async { final response = await http.get(Uri.parse('https://example.com/your_image.png')); final Uint8List bytes = response.bodyBytes; final ui.Codec codec = await ui.instantiateImageCodec(bytes); final ui.FrameInfo frameInfo = await codec.getNextFrame(); setState(() { _imageSize = Size(frameInfo.image.width.toDouble(), frameInfo.image.height.toDouble()); }); } @override Widget build(BuildContext context) { return Scaffold( appBar: AppBar(title: Text('Network Image Size Demo')), body: Center( child: _imageSize == null ? CircularProgressIndicator() : Text('Width: ${_imageSize!.width}, Height: ${_imageSize!.height}'), ), ); } } 

5. Flutter calculate image dimensions on initial load

   Description: Calculate image dimensions when the image is initially loaded.

   Code:

   import 'package:flutter/material.dart'; import 'package:flutter/services.dart'; import 'dart:ui' as ui; class InitialLoadImageSizeDemo extends StatefulWidget { @override _InitialLoadImageSizeDemoState createState() => _InitialLoadImageSizeDemoState(); } class _InitialLoadImageSizeDemoState extends State<InitialLoadImageSizeDemo> { ui.Image? _image; @override void initState() { super.initState(); _loadImage(); } Future<void> _loadImage() async { final ByteData data = await rootBundle.load('assets/your_image.png'); final Uint8List bytes = data.buffer.asUint8List(); final ui.Codec codec = await ui.instantiateImageCodec(bytes); final ui.FrameInfo frameInfo = await codec.getNextFrame(); setState(() { _image = frameInfo.image; }); } @override Widget build(BuildContext context) { return Scaffold( appBar: AppBar(title: Text('Initial Load Image Size Demo')), body: Center( child: _image == null ? CircularProgressIndicator() : Text('Image Width: ${_image!.width}, Height: ${_image!.height}'), ), ); } } 

6. Flutter get image size using flutter_image_compress``

   Description: Get image dimensions using the flutter_image_compress package.

   Code:

   import 'package:flutter/material.dart'; import 'package:flutter/services.dart'; import 'package:flutter_image_compress/flutter_image_compress.dart'; import 'dart:typed_data'; class ImageCompressSizeDemo extends StatefulWidget { @override _ImageCompressSizeDemoState createState() => _ImageCompressSizeDemoState(); } class _ImageCompressSizeDemoState extends State<ImageCompressSizeDemo> { Size? _imageSize; @override void initState() { super.initState(); _getImageSize(); } Future<void> _getImageSize() async { final ByteData data = await rootBundle.load('assets/your_image.png'); final Uint8List bytes = data.buffer.asUint8List(); final result = await FlutterImageCompress.compressWithList(bytes); final image = await decodeImageFromList(result); setState(() { _imageSize = Size(image.width.toDouble(), image.height.toDouble()); }); } @override Widget build(BuildContext context) { return Scaffold( appBar: AppBar(title: Text('Image Compress Size Demo')), body: Center( child: _imageSize == null ? CircularProgressIndicator() : Text('Width: ${_imageSize!.width}, Height: ${_imageSize!.height}'), ), ); } } 

7. Flutter image dimensions in a GridView

   Description: Determine the dimensions of images used in a GridView.

   Code:

   import 'package:flutter/material.dart'; import 'dart:ui' as ui; import 'package:flutter/services.dart'; class GridImageSizeDemo extends StatefulWidget { @override _GridImageSizeDemoState createState() => _GridImageSizeDemoState(); } class _GridImageSizeDemoState extends State<GridImageSizeDemo> { List<Size> _imageSizes = []; @override void initState() { super.initState(); _loadImages(); } Future<void> _loadImages() async { // Load images and get their sizes final imagePaths = ['assets/your_image1.png', 'assets/your_image2.png']; for (var path in imagePaths) { final ByteData data = await rootBundle.load(path); final Uint8List bytes = data.buffer.asUint8List(); final ui.Codec codec = await ui.instantiateImageCodec(bytes); final ui.FrameInfo frameInfo = await codec.getNextFrame(); _imageSizes.add(Size(frameInfo.image.width.toDouble(), frameInfo.image.height.toDouble())); } setState(() {}); } @override Widget build(BuildContext context) { return Scaffold( appBar: AppBar(title: Text('Grid Image Size Demo')), body: GridView.builder( gridDelegate: SliverGridDelegateWithFixedCrossAxisCount( crossAxisCount: 2, ), itemCount: _imageSizes.length, itemBuilder: (context, index) { final size = _imageSizes[index]; return Card( child: Center( child: Text('Width: ${size.width}, Height: ${size.height}'), ), ); }, ), ); } } 

8. Flutter get image dimensions from an AssetImage

   Description: Obtain image dimensions from an AssetImage directly.

   Code:

   import 'package:flutter/material.dart'; import 'package:flutter/services.dart'; import 'dart:ui' as ui; class AssetImageSizeDemo extends StatefulWidget { @override _AssetImageSizeDemoState createState() => _AssetImageSizeDemoState(); } class _AssetImageSizeDemoState extends State<AssetImageSizeDemo> { Size? _imageSize; @override void initState() { super.initState(); _getImageSize(); } Future<void> _getImageSize() async { final image = AssetImage('assets/your_image.png'); final ImageStream stream = image.resolve(ImageConfiguration.empty); final ImageInfo info = await stream.first; setState(() { _imageSize = Size(info.image.width.toDouble(), info.image.height.toDouble()); }); } @override Widget build(BuildContext context) { return Scaffold( appBar: AppBar(title: Text('Asset Image Size Demo')), body: Center( child: _imageSize == null ? CircularProgressIndicator() : Text('Width: ${_imageSize!.width}, Height: ${_imageSize!.height}'), ), ); } } 

9. Dart Flutter measure image size in a FutureBuilder

   Description: Measure image dimensions using FutureBuilder to handle async operations.

   Code:

   import 'package:flutter/material.dart'; import 'dart:ui' as ui; import 'package:flutter/services.dart'; class FutureBuilderImageSizeDemo extends StatelessWidget { Future<Size> _getImageSize() async { final ByteData data = await rootBundle.load('assets/your_image.png'); final Uint8List bytes = data.buffer.asUint8List(); final ui.Codec codec = await ui.instantiateImageCodec(bytes); final ui.FrameInfo frameInfo = await codec.getNextFrame(); return Size(frameInfo.image.width.toDouble(), frameInfo.image.height.toDouble()); } @override Widget build(BuildContext context) { return Scaffold( appBar: AppBar(title: Text('FutureBuilder Image Size Demo')), body: FutureBuilder<Size>( future: _getImageSize(), builder: (context, snapshot) { if (snapshot.connectionState == ConnectionState.waiting) { return Center(child: CircularProgressIndicator()); } if (snapshot.hasError) { return Center(child: Text('Error: ${snapshot.error}')); } final size = snapshot.data!; return Center( child: Text('Width: ${size.width}, Height: ${size.height}'), ); }, ), ); } } 

10. Flutter get image size before displaying it

    Description: Determine the dimensions of an image before displaying it in a widget.

    Code:

    import 'package:flutter/material.dart'; import 'dart:ui' as ui; import 'package:flutter/services.dart'; class PreDisplayImageSizeDemo extends StatefulWidget { @override _PreDisplayImageSizeDemoState createState() => _PreDisplayImageSizeDemoState(); } class _PreDisplayImageSizeDemoState extends State<PreDisplayImageSizeDemo> { Size? _imageSize; @override void initState() { super.initState(); _loadImage(); } Future<void> _loadImage() async { final ByteData data = await rootBundle.load('assets/your_image.png'); final Uint8List bytes = data.buffer.asUint8List(); final ui.Codec codec = await ui.instantiateImageCodec(bytes); final ui.FrameInfo frameInfo = await codec.getNextFrame(); setState(() { _imageSize = Size(frameInfo.image.width.toDouble(), frameInfo.image.height.toDouble()); }); } @override Widget build(BuildContext context) { return Scaffold( appBar: AppBar(title: Text('Pre-Display Image Size Demo')), body: Center( child: _imageSize == null ? CircularProgressIndicator() : Image.asset('assets/your_image.png'), ), ); } } 

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