Guardar todos los sprites de una textura recortados dentro de la herramienta de Unity como imagenes separadas png para usarlo en otra herramienta

SpriteToTexture.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEditor;
using System.IO;

public class SpriteToTexture : EditorWindow
{
	private Texture2D Atlas;

	[MenuItem("Window/SpriteToTexture")]
	public static void Init()
	{
		EditorWindow.GetWindow(typeof(SpriteToTexture), true, "Sprite To Texture");
	}

	void OnGUI()
	{
		Atlas = (Texture2D)EditorGUILayout.ObjectField("Atlas", Atlas, typeof(Texture2D), false);

		if (Atlas) //Ya se asigno una textura?
		{
			if (GUILayout.Button("Convert"))
			{
				ConvertAtlas2Prefabs();
			}
		}
	}

	void ConvertAtlas2Prefabs()
	{
		string path= AssetDatabase.GetAssetPath(Atlas);
		//Se  puede leer?
		try
		{
			Atlas.GetPixel(0, 0);
		}
		catch(UnityException e)
		{
			if(e.Message.StartsWith("Texture '" + Atlas.name + "' is not readable"))
			{
				//No se puede leer, avisamos y preguntamos si convertimos o cancelamos
				bool Convertir = EditorUtility.DisplayDialog ("Error", "La imagene tiene que estar habilitado 'Read/Write Enabled'", "Convertir", "Cancelar");
				if (Convertir)
				{
					//Lo hacemos que se puede leer
					TextureImporter importer = AssetImporter.GetAtPath (path) as TextureImporter;
					importer.isReadable = true;
					AssetDatabase.ImportAsset (path);
				}
				else
				{
					//Cancelo
					return;
				}
			}
		}

		//Tomamos todos los sprites
		Object[] atlasAssets = AssetDatabase.LoadAllAssetsAtPath(path);

		//Convertimos a png y guardamos
		float progressActual = 0;
		foreach (Object asset in atlasAssets)
		{
			EditorUtility.DisplayProgressBar("Converting", "Converting Sprites to Textures", progressActual / atlasAssets.LongLength);
			if (AssetDatabase.IsSubAsset(asset))
			{
				//Convertimos
				Texture2D img = ConvertSpriteToTexture (asset as Sprite);
				//Generamos PNG
				byte[] pngData = img.EncodeToPNG();
				if (pngData != null)
				{
					//Guardamos imagen
					File.WriteAllBytes(path + asset.name + ".png", pngData);
				}
			}
			progressActual++;
		}
		if (progressActual != 0)
			EditorUtility.ClearProgressBar();

		AssetDatabase.Refresh();
		this.Close();
	}

	//Ayuda obtener la carpeta
	string GetFolder(string _path)
	{
		return _path.Remove(_path.LastIndexOf("/"));
	}

	//Covnierte el sprite a textura
	static Texture2D ConvertSpriteToTexture(Sprite sprite)
	{
		try
		{
			if (sprite.rect.width != sprite.texture.width)
			{
				Texture2D newText = new Texture2D((int)sprite.rect.width, (int)sprite.rect.height);
				Color[] newColors = sprite.texture.GetPixels((int)System.Math.Ceiling(sprite.textureRect.x),
					(int)System.Math.Ceiling(sprite.textureRect.y),
					(int)System.Math.Ceiling(sprite.textureRect.width),
					(int)System.Math.Ceiling(sprite.textureRect.height));
				newText.SetPixels(newColors);
				newText.Apply();
				return newText;
			}
			else
				return sprite.texture;
		}catch
		{
			return sprite.texture;
		}
	}
}