CdxImageCache

A flexible, lightweight and customizable in-memory image caching service for Flutter. Optimized for decoding and caching ui.Image instances in memory. Ideal for prefetching, smooth scroll performance, and low-latency rendering.

Supports LRU (Least Recently Used) and no-eviction strategies.

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Features

• In-memory caching of both raw image bytes (Uint8List) and decoded ui.Image.
• Pluggable caching strategies: simple map or LRU (with byte size limit).
• Supports prefetching with deduplication and awaitable in-flight fetches.
• Customizable fetch and decode logic (e.g., via HTTP or local assets).
• Built-in default decoder using Flutter's image codec.
• Manual or automatic cache eviction.
• Stateless widget for displaying cached images (CachedImageMemory) with:
  • Fade-in animation.
  • Custom loading and error widgets.
  • Ready/error callbacks.
• No disk caching: built for fast runtime memory access.

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Getting started

1. Add the dependency

dependencies:
  cdx_image_cache: ^0.0.3

2. Usage

Initialize the singleton

final cache = MemoryImageCacheService();
cache.init(
  strategy: ImageCacheStrategy.lru(maxSizeBytes: 100 * 1024 * 1024), // 100MB
  fetchFunction: (url) async {
    final response = await http.get(Uri.parse(url));
    if (response.statusCode == 200) return response.bodyBytes;
    throw Exception('Failed to fetch image');
  },
);

You can use any HTTP client or custom logic in the fetcher.

Prefetch on model creation

class Article {
  final String imageUrl;

  Article.fromJson(Map<String, dynamic> json)
      : imageUrl = json['image'] {
    imageCacheService.prefetch(imageUrl);
  }
}

Wait for all prefetches to complete

await imageCacheService.waitForAllPrefetches()

Perfect for splash screens or onboarding screens that load bulk content.

Show the image with CachedImageMemory

CachedImageMemory(
    url: article.imageUrl,
    cacheService: imageCacheService,
    fadeDuration: Duration(milliseconds: 400),
    builder: (context, data) => Image.memory(data, fit: BoxFit.cover),
    loadingBuilder: (context) => const CircularProgressIndicator(),
    errorBuilder: (context, error) => const Icon(Icons.broken_image),
    onReady: (data) => print('Image ready!'),
)

This widget is stateless and uses TweenAnimationBuilder for fade-in.

Cache Strategies

abstract class ImageCacheStrategy {
  factory ImageCacheStrategy.simple();
  factory ImageCacheStrategy.lru({required int maxSizeBytes});
}

LRU

Removes least recently used items when maxEntries is exceeded.

NoEviction

Grows unbounded. Use with caution.

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API

ImageMemoryCacheService

ImageMemoryCacheService({
  required CacheStrategy strategy,
  required Future<Uint8List> Function(String url) fetcher,
  Duration timeout = const Duration(seconds: 15),
});

Methods:

• Uint8List? getIfAvailable(String url)
• ui.Image? getDecodedIfAvailable(String url)
• Future<ui.Image?> getDecodedImage(String url)
• void prefetchImages(Iterable<String> urls)
• Future<void> waitForAllFetches()
• void clearCache({String? url})

License

MIT

Author

Developed by Codedix