Added #

• ThumbHash.fromBase64Async() - Create ThumbHash from base64 string with pre-decoded RGBA in isolate

Added #

• Async methods - All CPU-intensive operations now have async versions that run in separate isolates, keeping the UI responsive:
  • thumbHashToRGBAAsync() - Decode ThumbHash asynchronously
  • rgbaToThumbHashAsync() - Encode RGBA to ThumbHash asynchronously
  • thumbHashImageToPngAsync() - Encode PNG asynchronously
  • ThumbHash.toRGBAAsync() - Decode with caching, off main thread
  • ThumbHash.toPngBytesAsync() - Get PNG bytes, off main thread
  • ThumbHash.toImageAsync() - Get ImageProvider, off main thread

Changed #

• Minimum Dart SDK version updated to 2.19.0 (required for Isolate.run())

Fixed #

• Added validation to detect truncated or corrupted ThumbHash bytes before decoding, throwing a descriptive ArgumentError instead of crashing with index-out-of-bounds errors
• Added errorBuilder to internal placeholder Image widget to gracefully handle decode failures by showing an empty widget

Changed #

• BREAKING: ThumbHashPlaceholder.errorWidget is now errorBuilder with signature Widget Function(BuildContext context, Object error, StackTrace? stackTrace). This provides access to the error details and build context for better error handling.

Added #

• ImageErrorWidgetBuilder typedef for the error builder function

Added #

• Initial release of fast_thumbhash
• Ultra-fast ThumbHash decoder (7x faster than naive implementation)
• Fast PNG encoder with pre-allocated buffers (1.6x faster)
• Full ThumbHash API support:
  • thumbHashToRGBA() - Decode ThumbHash to RGBA image
  • rgbaToThumbHash() - Encode RGBA image to ThumbHash
  • thumbHashToAverageRGBA() - Extract average color
  • thumbHashToApproximateAspectRatio() - Get aspect ratio
• Flutter ThumbHash convenience class with:
  • ThumbHash.fromBase64() - Create from base64 string
  • ThumbHash.fromBytes() - Create from raw bytes
  • toImage() - Get Flutter ImageProvider
  • toAverageColor() - Get average color as Flutter Color
  • toAspectRatio() - Get aspect ratio
• Natural image loading widgets:
  • ThumbHashPlaceholder - Simple widget with automatic transitions
  • ThumbHashImageBuilder - Customizable builder for full control
  • TransitionConfig - Configure transition animations
• Transition effects:
  • Fade - Simple crossfade
  • Blur-to-sharp - Focus effect as image loads
  • Scale-up - Subtle zoom effect
  • None - Instant switch
• Full alpha channel support
• Comprehensive test suite (50+ tests)
• Performance benchmarks

Performance #

• Decode: ~12-17μs per image (7x faster than naive)
• PNG encode: ~13-20μs per image (1.6x faster than naive)
• Total pipeline: ~26-38μs per image

Optimizations #

• Separable 2D DCT/IDCT - ~5-7x fewer operations
• Pre-computed cosine tables
• Batched Adler-32 checksum (modulo every 5552 bytes)
• 256-entry CRC-32 table (single lookup per byte)