flutter-assets-compress

name	flutter-assets-compress
description	Generate Flutter 1x and 2x image assets from existing 3.0x sources using a pure Dart script, compress PNG/JPG/WebP outputs, and update an AppImages asset index. Use when the user asks to normalize Flutter image assets, derive lower-density assets from @3x files, or create tool/image_assets.dart without external CLI tools.
license	MIT
metadata	{"author":"ducafecat","version":"1.0.1","compatibility":"Requires a Flutter or Dart project with assets/images/3.0x source images. Script execution requires Dart SDK and package dependencies image ^4.8.0 and path ^1.9.1."}

Flutter Assets Compress

Purpose

Create a pure Dart image asset tool for Flutter projects that:

• scans assets/images/3.0x/
• generates assets/images/2.0x/<name> at two-thirds size
• generates assets/images/<name> at one-third size
• compresses supported image outputs
• writes lib/core/assets/app_images.dart

Use this skill when

• The user wants to generate 1x and 2x assets from 3x Flutter images.
• The source images live under assets/images/3.0x/.
• The user wants a repeatable Dart script at tool/image_assets.dart.
• The user requires image processing without ImageMagick, pngquant, cwebp, or other external CLI tools.

Do not use this skill when

• The project has no Flutter-style asset directory.
• The user wants manual design editing rather than deterministic resizing.
• The source images are not available.
• The user requires external compression tools.

Required inputs

Identify or confirm:

1. Project root.
2. assets/images/3.0x/ source directory.
3. Existing pubspec.yaml.
4. Existing tool/image_assets.dart, if present.
5. Existing lib/core/assets/app_images.dart, if present.

Dependencies

Ensure these Dart dependencies are available:

dependencies:
  image: ^4.8.0
  path: ^1.9.1

Workflow

1. Inspect existing assets

Scan assets/images/3.0x/ and process image files only.

Supported outputs:

• PNG: encodePng(level: 6)
• JPG/JPEG: encodeJpg(quality: 85)
• WebP, when supported by the Dart image package: quality 80

Ignore non-image files.

2. Create or update the script

Create tool/image_assets.dart if it does not exist. If it already exists, read it first and merge only the required behavior.

The script must:

• use only Dart packages, not system commands
• create missing output directories
• overwrite duplicate output files
• skip unreadable images and print a warning
• produce a summary with total images and successful images
• write lib/core/assets/app_images.dart

3. Generate the asset index

Write constants for generated 1x image paths:

abstract final class AppImages {
  AppImages._();

  static const defaultPng = 'assets/images/default.png';
  static const homePlaceholderPng = 'assets/images/home_placeholder.png';
}

Convert asset paths to lower camel case names and include the extension in the constant name when useful to avoid collisions.

4. Run the script

Run:

dart run tool/image_assets.dart

Report:

• changed directory structure
• total source images
• successful outputs
• skipped files
• generated AppImages example

Safety rules

• Do not call external CLI image tools.
• Do not delete source images.
• Do not modify unrelated assets.
• Do not install packages without permission when network access is required.
• Preserve existing custom script behavior when merging.

Definition of done

The task is complete when:

• tool/image_assets.dart exists and is runnable.
• 1x and 2x assets are generated from all readable 3x images.
• lib/core/assets/app_images.dart is updated.
• Failures are reported without stopping the whole batch.
• The final report includes processing statistics.