pin73 / thumbhash Goto Github PK

import 'dart:async';

import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'package:thumbhash/thumbhash.dart' as thumb;
import 'dart:ui' as ui;

Future<ui.Image> thumbHashDecodeImage({
  required Uint8List thumbHash,
}) async {
  final completer = Completer<ui.Image>();

  final image = thumb.thumbHashToRGBA(thumbHash);
  ui.decodeImageFromPixels(image.rgba, image.width, image.height,
      ui.PixelFormat.rgba8888, completer.complete);

  return completer.future;
}

class ThumbHashImage extends ImageProvider<ThumbHashImage> {
  /// Creates an object that decodes a [thumbHash] as an image.
  ///
  /// The arguments must not be null.
  const ThumbHashImage(this.thumbHash, {this.scale = 1.0});

  /// The bytes to decode into an image.
  final Uint8List thumbHash;

  /// The scale to place in the [ImageInfo] object of the image.
  final double scale;

  @override
  Future<ThumbHashImage> obtainKey(ImageConfiguration configuration) =>
      SynchronousFuture<ThumbHashImage>(this);

  @override
  ImageStreamCompleter load(ThumbHashImage key, DecoderCallback decode) =>
      OneFrameImageStreamCompleter(_loadAsync(key));

  Future<ImageInfo> _loadAsync(ThumbHashImage key) async {
    assert(key == this);
    final image = await thumbHashDecodeImage(
      thumbHash: thumbHash,
    );
    return ImageInfo(image: image, scale: key.scale);
  }

  @override
  bool operator ==(Object other) => other.runtimeType != runtimeType
      ? false
      : other is ThumbHashImage &&
          memEquals(thumbHash, other.thumbHash) &&
          other.scale == scale;

  @override
  int get hashCode => thumbHash.reduce((value, element) => value + element.hashCode);

  @override
  String toString() => '$runtimeType($thumbHash, scale: $scale)';
}

bool memEquals(Uint8List bytes1, Uint8List bytes2) {
  if (identical(bytes1, bytes2)) {
    return true;
  }

  if (bytes1.lengthInBytes != bytes2.lengthInBytes) {
    return false;
  }

  // Treat the original byte lists as lists of 8-byte words.
  var numWords = bytes1.lengthInBytes ~/ 8;
  var words1 = bytes1.buffer.asUint64List(0, numWords);
  var words2 = bytes2.buffer.asUint64List(0, numWords);

  for (var i = 0; i < words1.length; i += 1) {
    if (words1[i] != words2[i]) {
      return false;
    }
  }

  // Compare any remaining bytes.
  for (var i = words1.lengthInBytes; i < bytes1.lengthInBytes; i += 1) {
    if (bytes1[i] != bytes2[i]) {
      return false;
    }
  }

  return true;
}