For Stackoverflow

using System.Collections;
using System.Collections.Generic;
using System.IO;
using UnityEngine;
using UnityEngine.UI;
//  Optimise theory - Since the world generates as 1 pixel = a block, optimise by only loading in blocks that are currently visible to the player camera
//  Or, use multiple pixels to load blocks instead of 1 pixel per block
public class ReadImage : MonoBehaviour
{
    [SerializeField]
    private Texture2D[] _images;
    private Texture2D _image;
    [SerializeField]
    private GameObject _wall;
    [SerializeField]
    private GameObject _ground;
    private string _imagesDir = "/LevelImages";
    [SerializeField]
    private Text _levelText;
    [SerializeField]
    private float _scale;

    private List<GameObject> groundObjectsToCombine = new List<GameObject>();
    private List<GameObject> wallObjectsToCombine = new List<GameObject>();

    public GameObject[] groundObjects;
    public GameObject[] wallObjects;

    private void Start()
    {
        string dataPath = Application.persistentDataPath;
        _imagesDir = dataPath + _imagesDir;

        if(Directory.Exists(_imagesDir))
        {
            Debug.Log("Dir exists!");
            string[] filesFound = Directory.GetFiles(_imagesDir);
            if(filesFound.Length > 0)
            {
                _images = new Texture2D[filesFound.Length];
                int counter = 0;
                foreach(string fileAndPath in filesFound)
                {
                    string fileName = fileAndPath.Substring(fileAndPath.LastIndexOf("\\") + 1);                 // Returns name of the file
                    string filePath = _imagesDir + "/" + fileName;                                              // Returns full location of file plus it's name


                    if (File.Exists(filePath))
                    {
                        Debug.Log("File exists!");
                        byte[] imageData = File.ReadAllBytes(filePath);                                         // Input all image data into bytes array
                        Texture2D levelTex = new Texture2D(1, 1);                                               // Create a new texture file
                        levelTex.LoadImage(imageData);                                                          // Load byte array (image data) into texture file
                        _images[counter] = levelTex;                                                            // Set current image in array position to = current texture
                        counter++;                                                                              // Increase array position counter
                        //_levelText.text = filePath.ToString();
                    }
                    else
                    {
                        Debug.Log("File not found: " + filePath);
                    }
                }
                GenerateImage(_images[Random.Range(0, _images.Length)]);                                        // Run GenerateImage function from random texture in images array

            }
            else
            {
                Debug.LogWarning("No files found in directory! Looking for files at dir: " + _imagesDir);       // Warning log - No files in directory
            }
        }

        else
        {
            Debug.LogError("Dir does not exist! Trying to find: " + _imagesDir);                                // Error log - Directory does not exist
        }
    }

    private void GenerateImage(Texture2D _image)
    {
        Color[] pixel = _image.GetPixels();                                                                     // Set color array for all pixels in image

        int mapX = _image.width;                                                                                // Set map size by image width and height
        int mapZ = _image.height;

        Vector3[] spawnPositions = new Vector3[(pixel.Length)];                                                 // Set Vector3 array for spawn positions to = how many pixels exist
        Debug.Log("Amount of pixels = " + pixel.Length);
        Vector3 startSpawnPosition = new Vector3(-Mathf.Round(mapX / 2), 0, -Mathf.Round(mapZ / 2) * _scale);            // Set start position
        Vector3 currentSpawnPosition = startSpawnPosition;                                                      // Ensure current position is the start position
        int counter = 0;

        for (int z = 0; z < mapZ; z++)
        {
            for (int x = 0; x < mapX; x++)
            {
                spawnPositions[counter] = currentSpawnPosition;                                                 // Moves position of image generator along in a left to right then up 'S pattern'
                counter++;
                currentSpawnPosition.x+= _scale;
            }

            currentSpawnPosition.x = startSpawnPosition.x;
            currentSpawnPosition.z+= _scale;
        }


        foreach (Vector3 pos in spawnPositions)                                                                 // For each spawn position
        {
            counter = 1;
            int arraycounter = 0;
            Color colour = pixel[counter];                                                                      // Check colour of pixel at counter position
            if (colour.Equals(Color.white))                                                                     // If colour of pixel is white
            {
                Transform spawnedTransform = Instantiate(_wall, pos, Quaternion.identity).transform;            // Spawn wall for white pixel
                spawnedTransform.localScale = Vector3.one * _scale;
                spawnedTransform.localScale = new Vector3(_scale, 3, _scale);
                //spawnedTransform.transform.parent = gameObject.transform;
                groundObjectsToCombine.Add(spawnedTransform.gameObject);                                          // Add object to list for wall objects to be mesh combined
                Debug.Log(arraycounter);
                groundObjects[arraycounter] = spawnedTransform.gameObject;
                spawnedTransform.transform.SetParent(groundObjects[arraycounter].transform);
            }

            else if (colour.Equals(Color.black))                                                                // If colour of pixel is black
            {
                Transform spawnedTransform = Instantiate(_ground, pos, Quaternion.identity).transform;          // Spawn ground for black pixel
                spawnedTransform.localScale = Vector3.one * _scale;
                //spawnedTransform.transform.parent = gameObject.transform;
                groundObjectsToCombine.Add(spawnedTransform.gameObject);                                        // Add object to list for ground objects to be mesh combined
                Debug.Log(arraycounter);
                groundObjects[arraycounter] = spawnedTransform.gameObject;
                spawnedTransform.transform.SetParent(groundObjects[arraycounter].transform);
            }

            else
            {
                Transform spawnedTransform = Instantiate(_ground, pos, Quaternion.identity).transform;          // Spawn ground for undefined pixel
                spawnedTransform.localScale = Vector3.one * _scale;
                //spawnedTransform.transform.parent = gameObject.transform;
                groundObjectsToCombine.Add(spawnedTransform.gameObject);                                        // Add object to list for ground objects to be mesh combined
                Debug.Log(arraycounter);
                groundObjects[arraycounter] = spawnedTransform.gameObject;
                spawnedTransform.transform.SetParent(groundObjects[arraycounter].transform);
            }
            counter++;                                                                                          // Increase counter
            arraycounter++;
        }

        for (int i = 0; i < groundObjects.Length; i++)
        {
            CombineGroundMeshes(groundObjects[i]);
        }

        // BELOW IS A DEBUG FUNCTION AND IS NOT REQUIRED FOR IMAGE GENERATOR - THIS FUNCTION COUNTS BLACK AND WHITE PIXELS IN INPUT IMAGE
        int black = 0;
        int white = 1;

        foreach (Color colour in pixel)
        {
            if (colour.Equals(Color.white))
            {
                white++;
            }

            else if (colour.Equals(Color.black))
            {
                black++;
            }
        }

        Debug.Log("White = " + white);
        Debug.Log("Black = " + black);
    }

    private void CombineGroundMeshes(GameObject groundobj)
    {
        Debug.Log("I got here");
        Vector3 position = groundobj.transform.position;
        groundobj.transform.position = Vector3.zero;

        MeshFilter[] meshfilters = groundobj.GetComponentsInChildren<MeshFilter>();
        CombineInstance[] combine = new CombineInstance[meshfilters.Length];
        int amt = 1;
        while(amt < meshfilters.Length)
        {
            combine[amt].mesh = meshfilters[amt].sharedMesh;
            combine[amt].transform = meshfilters[amt].transform.localToWorldMatrix;
            meshfilters[amt].gameObject.SetActive(false);
            amt++;
        }

        groundobj.transform.GetComponent<MeshFilter>().mesh = new Mesh();
        groundobj.transform.GetComponent<MeshFilter>().mesh.CombineMeshes(combine, true, true);
        groundobj.transform.gameObject.SetActive(true);

        groundobj.transform.position = position;
        groundobj.AddComponent<MeshCollider>();
    }
}