Do not completely decode the image file, just read the metadata to get the image width and height.

Just support jpeg, gif, png, webp, bmp.


Image of File

import 'dart:io';

import 'package:image_size_getter/image_size_getter.dart';
import 'package:image_size_getter/file_input.dart'; // For compatibility with flutter web.

void main(List<String> arguments) async {
  final file = File('asset/IMG_20180908_080245.jpg');
  final size = ImageSizeGetter.getSize(FileInput(file));
  print('jpg = $size');

  final pngFile = File('asset/ic_launcher.png');
  final pngSize = ImageSizeGetter.getSize(FileInput(pngFile));
  print('png = $pngSize');

  final webpFile = File('asset/demo.webp');
  final webpSize = ImageSizeGetter.getSize(FileInput(webpFile));
  print('webp = $webpSize');

  final gifFile = File('asset/dialog.gif');
  final gifSize = ImageSizeGetter.getSize(FileInput(gifFile));
  print('gif = $gifSize');

Image of Memory

import 'package:image_size_getter/image_size_getter.dart';

void foo(Uint8List image){
  final memoryImageSize = ImageSizeGetter.getSize(MemoryInput(image));
  print('memoryImageSize = $memoryImageSize');

Image of Http

See HttpInput.

About Size

The size contains width and height.

But some image have orientation. Such as jpeg, when the orientation of exif is 5, 6, 7 or 8, the width and height will be swapped.

We can use next code to get width and height.

void foo(File file) {
  final size = ImageSizeGetter.getSize(FileInput(file));
  if (size.needRotate) {
    final width = size.height;
    final height = size.width;
    print('width = $width, height = $height');
  } else {
    print('width = ${size.width}, height = ${size.height}');


If your data source is read asynchronously, consider using AsyncImageInput.

A typical use case is http_input.


We can implement our own input or decoder.

In addition to several built-in implementations, subsequent implementations will also be added to the project through plugin.

Custom Input

Such as: http_input.

In addition, if your picture has verification, for example, you need to use the request header to access it, or you need a post request to get it, you need to customize input.

Custom Decoder

Such as bmp decoder

Check the file type:


The width and height:


So, we can write code with:

import 'package:image_size_getter/image_size_getter.dart';

class BmpDecoder extends BaseDecoder {
  const BmpDecoder();

  String get decoderName => 'bmp';

  Size getSize(ImageInput input) {
    final widthList = input.getRange(0x12, 0x16);
    final heightList = input.getRange(0x16, 0x1a);

    final width = convertRadix16ToInt(widthList, reverse: true);
    final height = convertRadix16ToInt(heightList, reverse: true);
    return Size(width, height);

  Future<Size> getSizeAsync(AsyncImageInput input) async {
    final widthList = await input.getRange(0x12, 0x16);
    final heightList = await input.getRange(0x16, 0x1a);

    final width = convertRadix16ToInt(widthList, reverse: true);
    final height = convertRadix16ToInt(heightList, reverse: true);
    return Size(width, height);

  bool isValid(ImageInput input) {
    final list = input.getRange(0, 2);
    return _isBmp(list);

  Future<bool> isValidAsync(AsyncImageInput input) async {
    final list = await input.getRange(0, 2);
    return _isBmp(list);

  bool _isBmp(List<int> startList) {
    return startList[0] == 66 && startList[1] == 77;

Use it:

final bmp = File('../example/asset/demo.bmp');

const BmpDecoder decoder = BmpDecoder();
final input = FileInput(bmp);

expect(decoder.getSize(input), Size(256, 256));

Register custom decoder to image size getter

ImageSizeGetter.registerDecoder(const BmpDecoder());

The method can also be used to replace the default decoder.

For example, you think the existing JPEG format is not rigorous enough.

ImageSizeGetter.registerDecoder(const MyJpegDecoder());

Use decoder alone

Each decoder can be used alone.

void decodeWithImageInput(ImageInput input) {
  BaseDecoder decoder = const GifDecoder();
  final isGif = decoder.isValid(input);
  print('isGif: $isGif');

  if (isGif) {
    final size = decoder.getSize(input);
    print('size: $size');

void decodeWithAsyncImageInput(AsyncImageInput input) async {
  BaseDecoder decoder = const PngDecoder();
  final isPng = await decoder.isValidAsync(input);
  print('isPng: $isPng');

  if (isPng) {
    final size = await decoder.getSizeAsync(input);
    print('size: $size');


See migrate

Other question

The package is dart package, no just flutter package. So, if you want to get flutter asset image size, you must convert it to memory(Uint8List).

final buffer = await rootBundle.load('assets/logo.png'); // get the byte buffer
final memoryImageSize = ImageSizeGetter.getSize(MemoryInput.byteBuffer(buffer));
print('memoryImageSize = $memoryImageSize');


Apache 2.0