adjkit 0.2.0

A pure Dart codec for Adobe Photoshop Levels, Hue/Saturation, Selective Color, and Channel Mixer presets.

AdjKit

AdjKit is a pure Dart codec for Adobe Photoshop adjustment presets: Levels (.alv), Hue/Saturation (.ahu), Selective Color (.asv), Channel Mixer (.cha), and Black & White (.blw), plus Duotone Options (.ado). It has no Flutter or native-code dependency.

Supported data

• Levels (.alv) version 2 with 29 standard channel records and optional Photoshop CS extended records.
• Hue/Saturation (.ahu) version 2 with colorization, master settings, and six editable color ranges.
• Selective Color (.asv) version 1 with relative or absolute corrections and all ten records, including the reserved first record.
• Channel Mixer (.cha) version 1 with monochrome mode, four output rows, source-channel percentages, and constants.
• Black & White (.blw), a version 16 Action Descriptor with six colour contributions, the optional tint, and the preset kind; unknown descriptor items round-trip.
• Duotone Options (.ado) and duotone PSD color mode data: one to four inks with their colors or matching-system catalog codes, transfer curves, dot gain, and overprint colors, through AdjDuotoneDecoder and AdjDuotoneEncoder.
• Shared PsLevels, PsHueSaturation, PsSelectiveColor, PsChannelMixer, and PsBlackAndWhite settings from pscore.
• Strict and tolerant decoding with a configurable file-size limit, compatibility warnings, and retained trailing bytes.
• Encoding from settings and reusable dart:convert codecs and converters.

Reading a file

import 'dart:io';
import 'dart:typed_data';

import 'package:adjkit/adjkit.dart';

final File file = File('Strong Contrast.alv');
final Uint8List bytes = await file.readAsBytes();
final AdjPresetFile preset = AdjDecoder.decode(
  bytes,
  kind: AdjPresetKind.levels,
);

if (preset.settings case PsLevels(:final List<PsLevelRecord> records)) {
  final PsLevelRecord composite = records.first;
  print('Input ${composite.inputFloor}–${composite.inputCeiling}, gamma ${composite.gammaValue}');
}

for (final AdjWarning warning in preset.warnings) {
  print(warning.message);
}

The files carry no signature, so the caller must choose the kind. AdjPresetKind.fromExtension accepts extensions with or without a leading dot, ignores case, and returns null for unsupported extensions.

Writing a preset

final PsSelectiveColor settings = PsSelectiveColor(
  corrections: List.filled(
    PsSelectiveColor.correctionCount,
    const PsSelectiveColorCorrection(),
  ),
);

final Uint8List output = AdjEncoder.encode(settings);
await File('neutral.asv').writeAsBytes(output);

The settings type determines the output format. To save a decoded preset, pass preset.settings to AdjEncoder.encode. Encoding checks the required record counts and retains the model's version and trailing bytes; it does not apply the decoder's Photoshop dialog-range checks. Invalid record counts are reported through AdjWriteException.

Reusable dart:convert API

AdjCodec implements Codec<PsAdjustmentSettings, List<int>> and keeps the expected input kind and decoding policy together:

const AdjCodec codec = AdjCodec(
  kind: AdjPresetKind.levels,
  decodeOptions: AdjDecodeOptions(mode: AdjDecodeMode.strict),
);

final PsAdjustmentSettings settings = codec.decode(bytes);
final Uint8List output = codec.encode(settings);

The codec returns settings directly. Use AdjDecoder when warnings are also needed. kind selects the layout for decoding; encoding always follows the actual settings type.

The List<int> binary type allows composition with standard codecs such as base64; direct encode calls still return Uint8List. AdjEncoder and AdjDecoder are also reusable Converter implementations. Each conversion consumes or produces one complete in-memory preset.

Strict, tolerant, and bounded decoding

Tolerant decoding is the default. Unexpected main versions, trailing bytes, and out-of-range levels, master/range hue-saturation values, selective-color corrections, or channel-mixer values produce AdjWarning entries in AdjPresetFile.warnings.

Strict mode turns the first compatibility issue into an AdjFormatException:

final AdjPresetFile preset = AdjDecoder.decode(
  bytes,
  kind: AdjPresetKind.levels,
  options: const AdjDecodeOptions(mode: AdjDecodeMode.strict),
);

Truncated required fields and files exceeding AdjDecodeOptions.maxFileBytes always throw. The default file-size limit is 1 MiB.

The bundled example prints a preset summary and its warnings:

dart run example/main.dart 'Strong Contrast.alv'

Shared PSD settings

PsdKit's PsdLevelsAdjustment, PsdHueSaturationAdjustment, PsdSelectiveColorAdjustment, and PsdChannelMixerAdjustment extend the same PsCore settings types. Their settings can therefore be passed directly to AdjEncoder.encode. A host editor can use decoded preset settings when constructing its corresponding adjustment layer without translating to a second settings model.

Scope

AdjKit reads and writes presets but does not apply adjustments to pixels. Curves presets (.acv) have their own layout and are handled by AcvKit. Exposure and other undocumented preset layouts are not supported.

The layouts follow Adobe's specification and the shared PSD adjustment codec. Standalone Photoshop preset samples have not yet been used to verify compatibility; the Channel Mixer layout is derived from the PSD mixr block.

See docs/ADJUSTMENTS.md for the binary layouts, validation rules, encoding behavior, and integration guidance.

References

• Adobe Photoshop File Formats Specification

AdjKit is an independent implementation and is not affiliated with or endorsed by Adobe.

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