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:

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The width and height:

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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

LICENSE

Apache 2.0