zero_cached_image 1.4.0

A minimal, high-performance cached network image widget. Zero-copy disk reads via ImmutableBuffer.fromFilePath, in-memory index, ETag support. Only 2 dependencies.

zero_cached_image

A minimal, high-performance cached network image widget for Flutter. Zero-copy disk reads and only 2 dependencies.

How it works

Step	Approach
Cache lookup	In-memory Map (~11ns)
File loading	ImmutableBuffer.fromFilePath() (zero-copy, no Dart heap copy)
Widget layer	Flutter's built-in frameBuilder
Dependencies	2 (path_provider, crypto)

The in-memory index is loaded from a JSON file on startup and flushed to disk on changes (debounced, atomic writes with backup recovery). Cache survives app restarts.

Install

dependencies:
  zero_cached_image: ^1.0.0

Usage

Basic widget

ZeroCachedImage(
  imageUrl: 'https://example.com/photo.jpg',
  width: 200,
  height: 200,
  fit: BoxFit.cover,
)

With placeholder and error widget

ZeroCachedImage(
  imageUrl: 'https://example.com/photo.jpg',
  placeholder: (context, url) => const CircularProgressIndicator(),
  errorWidget: (context, url, error) => const Icon(Icons.error),
)

Fade animation

ZeroCachedImage(
  imageUrl: 'https://example.com/photo.jpg',
  fadeInDuration: const Duration(milliseconds: 300),  // default: 500ms
  fadeOutDuration: Duration.zero,                      // disable fade out
)

Custom headers

ZeroCachedImage(
  imageUrl: 'https://example.com/private.jpg',
  httpHeaders: {'Authorization': 'Bearer token'},
)

Image provider (for DecorationImage, precacheImage)

// In a BoxDecoration
Container(
  decoration: BoxDecoration(
    image: DecorationImage(
      image: ZeroCachedImageProvider('https://example.com/bg.jpg'),
      fit: BoxFit.cover,
    ),
  ),
)

// Precache
precacheImage(ZeroCachedImageProvider('https://example.com/photo.jpg'), context);

Cache management

// Evict a single image
ZeroCachedImage.evictFromCache('https://example.com/photo.jpg');

// Clear all cached images
ZeroCacheManager.instance.clear();

Custom cache configuration

// Override max cache size (default: 500MB)
ZeroCacheManager.instance = ZeroCacheManager(
  maxCacheSize: 200 * 1024 * 1024,  // 200MB
);

All widget parameters

Parameter	Type	Default	Description
imageUrl	String	required	The URL to load
width	double?	null	Widget width
height	double?	null	Widget height
fit	BoxFit?	null	How to fit the image
placeholder	Widget Function(BuildContext, String)?	null	Shown while loading
errorWidget	Widget Function(BuildContext, String, Object)?	null	Shown on error
fadeInDuration	Duration	500ms	Fade-in animation duration
fadeOutDuration	Duration	200ms	Fade-out animation duration
alignment	Alignment	center	Image alignment
httpHeaders	Map<String, String>?	null	Custom HTTP headers
cacheManager	ZeroCacheManager?	null	Custom cache manager
color	Color?	null	Color tint
colorBlendMode	BlendMode?	null	Blend mode for color tint
filterQuality	FilterQuality	low	Rendering quality

Features

• ETag / If-None-Match: Conditional requests skip re-download when the server confirms cache is fresh (304 Not Modified).
• Cache-Control max-age: Respects server expiry hints.
• LRU eviction: Oldest entries evicted when cache exceeds size limit (default 500MB, configurable).
• Concurrent deduplication: Multiple requests for the same URL share a single download.
• Atomic index writes: Index written to .tmp, then renamed. .bak backup for corruption recovery.
• Animated images: GIF and animated WebP supported.
• Web: Falls back to Image.network() since dart:io is unavailable on web.

Platforms

Works on all platforms where dart:io is available: Android, iOS, Windows, macOS, Linux. Web uses a fallback path (Image.network()).

License

MIT