TextureArrayCreator.cs

using UnityEngine;
using UnityEditor;

public class TextureArrayWizard : ScriptableWizard
{
	[SerializeField] private Texture2D[] textures = null;

	[MenuItem("Assets/Create/Texture Array")]
	static void CreateWizard()
	{
		var wiz = ScriptableWizard.DisplayWizard<TextureArrayWizard>("Create Texture Array", "Create");

		wiz.textures = new Texture2D[Selection.objects.Length];
		for(int i = 0; i < Selection.objects.Length; i++)
		{
			Texture2D tex = (Texture2D) Selection.objects[i];
			if(tex != null)
				wiz.textures[i] = tex;
		}
	}

	void OnWizardCreate()
	{
		if(textures.Length == 0)
			return;

		string path = EditorUtility.SaveFilePanelInProject("Save Texture Array", "Texture Array", "asset", "Save Texture Array");
		if(path.Length == 0)
			return;
		
		//Try to find an existing asset, to update instead of creating fresh
		var oldTexArray = AssetDatabase.LoadAssetAtPath(path, typeof(Texture2DArray));

		Texture2D t = textures[0];
		Texture2DArray tArray = new Texture2DArray(t.width, t.height, textures.Length, t.format, t.mipmapCount > 1);
		tArray.filterMode = t.filterMode;
		tArray.wrapMode = t.wrapMode;

		for(int i = 0; i < textures.Length; i++)
		{
			for(int m = 0; m < t.mipmapCount; m++)
			{
				Graphics.CopyTexture(textures[i], 0, m, tArray, i, m);
			}
		}

		if(oldTexArray != null)
		{
			AssetDatabase.RemoveObjectFromAsset(oldTexArray);
			AssetDatabase.AddObjectToAsset(tArray, path);
			AssetDatabase.ImportAsset(path, ImportAssetOptions.ForceUpdate);
			AssetDatabase.Refresh();
		}
		else
		{
			AssetDatabase.CreateAsset(tArray, path);
		}
	}
}