image_size_getter #

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.

Usage #

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}');
  }
}

AsyncImageInput #

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

A typical use case is http_input.

Custom #

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();

  @override
  String get decoderName => 'bmp';

  @override
  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);
  }

  @override
  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);
  }

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

  @override
  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);

assert(decoder.isValid(input));
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');
  }
}

migrate #

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');

LICENSE #

Apache 2.0