TextureExtensions.cs

using System.Collections;
using System.Collections.Generic;
using System.IO;
#if UNITY_EDITOR
using UnityEditor;
#endif
using UnityEngine;

public static class TextureExtensions
{
    public static void SetTextureImporterFormat(Texture2D texture, bool isReadable)
    {
#if UNITY_EDITOR
        if (null == texture) return;

        string assetPath = AssetDatabase.GetAssetPath(texture);
        var tImporter = AssetImporter.GetAtPath(assetPath) as TextureImporter;
        if (tImporter != null)
        {
            tImporter.textureType = TextureImporterType.Default;

            tImporter.isReadable = isReadable;

            AssetDatabase.ImportAsset(assetPath);
            AssetDatabase.Refresh();
        }
#endif
    }

    public static Texture2D LoadPNG(string filePath)
    {
        Texture2D tex = null;
        byte[] fileData;

        if (File.Exists(filePath))
        {
            fileData = File.ReadAllBytes(filePath);
            tex = new Texture2D(2, 2);
            tex.LoadImage(fileData); //..this will auto-resize the texture dimensions.
        }

        return tex;
    }
}