AssetPostprocessor.OnPreprocessTexture()

Description

Add this function to a subclass to get a notification just before the texture importer is run.

This lets you set up default values for the import settings.

Use this callback if you want to change the compression format of the texture.

using UnityEngine;
using UnityEditor;

// Automatically convert any texture file with "_bumpmap"
// in its file name into a normal map.

class MyTexturePostprocessor : AssetPostprocessor
{
    void OnPreprocessTexture()
    {
        if (assetPath.Contains("_bumpmap"))
        {
            TextureImporter textureImporter  = (TextureImporter)assetImporter;
            textureImporter.convertToNormalmap = true;
        }
    }
}