act_thumbhash 1.1.0

A pure Dart implementation of the ThumbHash image placeholder algorithm. Encode images into compact hashes and decode them into lossy previews.

1.1.0

• The minimum supported SDK is now Dart 3.8.

1.0.0

• Perf: the encoder and decoder now precompute their DCT basis tables and skip coefficients the format discards, making encoding roughly 9x and decoding roughly 4x faster. Output is byte-for-byte unchanged.
• Fix: decodeSync now validates the hash length against what its header requires and throws the documented ArgumentError for truncated input, instead of surfacing an out-of-bounds RangeError partway through decoding.
• Fix: decodeSync and decodeAsync now reject baseSize values below 1 with an ArgumentError, and small baseSize values can no longer round the decoded image's short side down to zero pixels.
• Fix: encoding images with an aspect ratio steeper than 128:1 no longer throws; the internal downscale now keeps the short side at a minimum of one pixel.
• Feat: Web support. dart:isolate is no longer imported unconditionally; on the web (both dart2js and dart2wasm) encodeAsync and decodeAsync run the computation on the event loop after yielding once, since isolates are unavailable there. Native behaviour is unchanged.
• Fix: encodeSync emitted too few luminance coefficients for images with an aspect ratio steeper than roughly 2.8:1 (2:1 with alpha), in either orientation. The resulting hashes were shorter than any decoder expects, so decoding them threw a RangeError, and they were not readable by other ThumbHash implementations. The luminance channel is now always encoded with at least 3 coefficients per axis, matching the reference implementation.
• Fix: the hash buffer was one byte too small for images with alpha whose coefficient count is odd (for example 100x75), making encodeSync throw a RangeError while writing its own output.

Hashes for images that encoded correctly before are unchanged.

1.0.0-dev.2

• Documentation and packaging updates

1.0.0-dev.1

• Initial pre-release
• Encode RGBA images to ThumbHash
• Decode ThumbHash to RGBA images
• Async methods using isolates
• Automatic downscaling for images larger than 128px