JSON Migrator to EAI2 (Python Script)

🧰 JSON Migrator to EAI2

This Python script allows you to migrate old importer folders (used by the ExtraAssetsImporter for Cities: Skylines II) into the new split format, using template-based overrides.

It can:

• Convert legacy surface.json, decal.json, and netlane.json files to the new Prefab.json + Material.json structure.
• Automatically fix pink Normal Maps for surfaces.
• Optionally convert textures to 8-bit to reduce file size (Enabled by default).
• Share identical textures across assets by replacing duplicates with a small JSON reference.

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📝 Notes

• The script automatically looks for _DefaultJson templates locally or in the default Cities: Skylines II LocalLow path.
• If templates are missing, it will raise an error and skip conversion for that format.
• The texture sharing step creates small .json files containing only a path property pointing to the shared texture location, to reduce disk usage.

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⚡ Quick Start

# Install dependencies
pip install pillow numpy imagequant

Place the script next to your old importer folders (e.g. CustomSurfaces, CustomDecals, CustomNetLanes) and run :

python JsonMigratorToEAI2.py

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📦 Installation

Make sure you have Python 3.8+ installed, then run:

# Install required libraries
pip install pillow numpy imagequant

🧼 Uninstallation

Remove the script from your hard drive and then run:

pip uninstall pillow numpy imagequant -y

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🚀 Basic Usage

Place the script next to your old importer folders (e.g. CustomSurfaces, CustomDecals, CustomNetLanes) and run:

python JsonMigratorToEAI2.py

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📝 Command-line Arguments

Argument	Required	Description
--format {surfaces,decals,netlanes}	✅ if using --input-dir or --output-dir	Specifies which asset type to process.
--input-dir DIR	❌	Path to old importer folder (processed recursively).
--output-dir DIR	❌	Output base directory. Defaults to Surfaces, Decals or NetLanesDecal depending on format.
--fail-fast	❌	Stop the script on the first error instead of continuing.
--force-8bit / --no-force-8bit	❌	Enable or disable automatic conversion of textures to 8-bit. Enabled by default.
--force-8bit-types {_BaseColorMap,_MaskMap,_NormalMap}	❌	Specify which texture types to apply 8-bit conversion to. Defaults to all three.

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🧪 Examples

1. Convert everything automatically

python JsonMigratorToEAI2.py

2. Convert only surfaces

python JsonMigratorToEAI2.py --format surfaces

2.1. Convert only surfaces from a specific folder

python JsonMigratorToEAI2.py --format surfaces --input-dir "C:\path\to\CustomSurfaces"

3. Convert only decals

python JsonMigratorToEAI2.py --format decals

4. Disable 8-bit conversion

python JsonMigratorToEAI2.py --no-force-8bit

5. Force 8-bit conversion only on BaseColorMap and NormalMap

python JsonMigratorToEAI2.py --force-8bit-types _BaseColorMap _NormalMap

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📁 Expected Folder Structure

MyModFolder/ 
├─ JsonMigratorToEAI2.py 
├─ CustomSurfaces/ 
│ └─ Category/AssetName/surface.json + textures 
├─ CustomDecals/ 
│ └─ ... 
├─ CustomNetLanes/ 
│ └─ ...

After migration, the output will look like: ( NOTE : I removed the old folder, but the script doesn't remove them)

MyModFolder/ 
├─ Surfaces/ 
│ └─ Category/AssetName/Prefab.json + Material.json + textures 
├─ Decals/ 
│ └─ ... 
├─ NetLanesDecal/ 
│ └─ ...

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🧠 License

MIT License — Feel free to modify and distribute this script.