source: binary-improvements2/MapRendering/src/MapRenderBlockBuffer.cs@ 419

using System;
using System.IO;
using Unity.Collections;
using UnityEngine;
using UnityEngine.Profiling;

namespace MapRendering {
        public class MapRenderBlockBuffer {
                private readonly Texture2D blockMap = new Texture2D (Constants.MapBlockSize, Constants.MapBlockSize, Constants.DefaultTextureFormat, false);
                private readonly MapTileCache cache;
                private readonly NativeArray<int> emptyImageData;
                private readonly Texture2D zoomBuffer = new Texture2D (Constants.MapBlockSize / 2, Constants.MapBlockSize / 2, Constants.DefaultTextureFormat, false);
                private readonly int zoomLevel;
                private readonly string folderBase;
                
                private Vector2i currentBlockMapPos = new Vector2i (int.MinValue, int.MinValue);
                private string currentBlockMapFolder = string.Empty;

                public MapRenderBlockBuffer (int _level, MapTileCache _cache) {
                        zoomLevel = _level;
                        cache = _cache;
                        folderBase = $"{Constants.MapDirectory}/{zoomLevel}/";

                        {
                                // Initialize empty tile data
                                Color nullColor = new Color (0, 0, 0, 0);
                                for (int x = 0; x < Constants.MapBlockSize; x++) {
                                        for (int y = 0; y < Constants.MapBlockSize; y++) {
                                                blockMap.SetPixel (x, y, nullColor);
                                        }
                                }

                                NativeArray<int> blockMapData = blockMap.GetRawTextureData<int> ();
                                emptyImageData = new NativeArray<int> (blockMapData.Length, Allocator.Persistent,
                                        NativeArrayOptions.UninitializedMemory);
                                blockMapData.CopyTo (emptyImageData);
                        }
                }

                public TextureFormat FormatSelf => blockMap.format;

                public void ResetBlock () {
                        currentBlockMapFolder = string.Empty;
                        currentBlockMapPos = new Vector2i (int.MinValue, int.MinValue);
                        cache.ResetTile (zoomLevel);
                }

                public void SaveBlock () {
                        Profiler.BeginSample ("SaveBlock");
                        try {
                                saveTextureToFile ();
                        } catch (Exception e) {
                                Log.Warning ($"Exception in MapRenderBlockBuffer.SaveBlock(): {e}");
                        }
                        Profiler.EndSample ();
                }

                public bool LoadBlock (Vector2i _block) {
                        Profiler.BeginSample ("LoadBlock");
                        lock (blockMap) {
                                if (currentBlockMapPos != _block) {
                                        Profiler.BeginSample ("LoadBlock.Strings");
                                        string folder;
                                        if (currentBlockMapPos.x != _block.x) {
                                                folder = $"{folderBase}{_block.x}/";

                                                Profiler.BeginSample ("LoadBlock.Directory");
                                                Directory.CreateDirectory (folder);
                                                Profiler.EndSample ();
                                        } else {
                                                folder = currentBlockMapFolder;
                                        }

                                        string fileName = $"{folder}{_block.y}.png";
                                        Profiler.EndSample ();
                                        
                                        SaveBlock ();
                                        loadTextureFromFile (fileName);

                                        currentBlockMapFolder = folder;
                                        currentBlockMapPos = _block;

                                        Profiler.EndSample ();
                                        return true;
                                }
                        }

                        Profiler.EndSample ();
                        return false;
                }

                public void SetPart (Vector2i _offset, int _partSize, Color32[] _pixels) {
                        if (_offset.x + _partSize > Constants.MapBlockSize || _offset.y + _partSize > Constants.MapBlockSize) {
                                Log.Error (
                                        $"MapBlockBuffer[{zoomLevel}].SetPart ({_offset}, {_partSize}, {_pixels.Length}) has blockMap.size ({Constants.MapBlockSize}/{Constants.MapBlockSize})");
                                return;
                        }

                        Profiler.BeginSample ("SetPart");
                        blockMap.SetPixels32 (_offset.x, _offset.y, _partSize, _partSize, _pixels);
                        Profiler.EndSample ();
                }

                public Color32[] GetHalfScaled () {
                        Profiler.BeginSample ("HalfScaled.ResizeBuffer");
                        zoomBuffer.Reinitialize (Constants.MapBlockSize, Constants.MapBlockSize);
                        Profiler.EndSample ();

                        Profiler.BeginSample ("HalfScaled.CopyPixels");
                        if (blockMap.format == zoomBuffer.format) {
                                Profiler.BeginSample ("Native");
                                NativeArray<byte> dataSrc = blockMap.GetRawTextureData<byte> ();
                                NativeArray<byte> dataZoom = zoomBuffer.GetRawTextureData<byte> ();
                                dataSrc.CopyTo (dataZoom);
                                Profiler.EndSample ();
                        } else {
                                Profiler.BeginSample ("GetSetPixels");
                                zoomBuffer.SetPixels32 (blockMap.GetPixels32 ());
                                Profiler.EndSample ();
                        }
                        Profiler.EndSample ();

                        Profiler.BeginSample ("HalfScaled.Scale");
                        TextureScale.Point (zoomBuffer, Constants.MapBlockSize / 2, Constants.MapBlockSize / 2);
                        Profiler.EndSample ();

                        Profiler.BeginSample ("HalfScaled.Return");
                        Color32[] result = zoomBuffer.GetPixels32 ();
                        Profiler.EndSample ();

                        return result;
                }

                public void SetPartNative (Vector2i _offset, int _partSize, NativeArray<int> _pixels) {
                        if (_offset.x + _partSize > Constants.MapBlockSize || _offset.y + _partSize > Constants.MapBlockSize) {
                                Log.Error (
                                        $"MapBlockBuffer[{zoomLevel}].SetPart ({_offset}, {_partSize}, {_pixels.Length}) has blockMap.size ({Constants.MapBlockSize}/{Constants.MapBlockSize})");
                                return;
                        }

                        Profiler.BeginSample ("SetPartNative");
                        NativeArray<int> destData = blockMap.GetRawTextureData<int> ();
                        
                        for (int y = 0; y < _partSize; y++) {
                                int srcLineStartIdx = _partSize * y;
                                int destLineStartIdx = blockMap.width * (_offset.y + y) + _offset.x;
                                for (int x = 0; x < _partSize; x++) {
                                        destData [destLineStartIdx + x] = _pixels [srcLineStartIdx + x];
                                }
                        }
                        Profiler.EndSample ();
                }

                public NativeArray<int> GetHalfScaledNative () {
                        Profiler.BeginSample ("HalfScaledNative.ResizeBuffer");
                        if (zoomBuffer.format != blockMap.format || zoomBuffer.height != Constants.MapBlockSize / 2 || zoomBuffer.width != Constants.MapBlockSize / 2) {
                                zoomBuffer.Reinitialize (Constants.MapBlockSize / 2, Constants.MapBlockSize / 2, blockMap.format, false);
                        }
                        Profiler.EndSample ();

                        Profiler.BeginSample ("HalfScaledNative.Scale");
                        ScaleNative (blockMap, zoomBuffer);
                        Profiler.EndSample ();

                        return zoomBuffer.GetRawTextureData<int> ();
                }
                
                private static void ScaleNative (Texture2D _sourceTex, Texture2D _targetTex) {
                        NativeArray<int> srcData = _sourceTex.GetRawTextureData<int> ();
                        NativeArray<int> targetData = _targetTex.GetRawTextureData<int> ();
                        
                        int oldWidth = _sourceTex.width;
                        int oldHeight = _sourceTex.height;
                        int newWidth = _targetTex.width;
                        int newHeight = _targetTex.height;
                        
                        float ratioX = (float) oldWidth / newWidth;
                        float ratioY = (float) oldHeight / newHeight;

                        for (int y = 0; y < newHeight; y++) {
                                int oldLineStart = (int) (ratioY * y) * oldWidth;
                                int newLineStart = y * newWidth;
                                for (int x = 0; x < newWidth; x++) {
                                        targetData [newLineStart + x] = srcData [(int) (oldLineStart + ratioX * x)];
                                }
                        }
                }

                private void loadTextureFromFile (string _fileName) {
                        Profiler.BeginSample ("LoadTexture");

                        Profiler.BeginSample ("LoadFile");
                        byte[] array = cache.LoadTile (zoomLevel, _fileName);
                        Profiler.EndSample ();

                        Profiler.BeginSample ("LoadImage");
                        if (array != null && blockMap.LoadImage (array) && blockMap.height == Constants.MapBlockSize &&
                            blockMap.width == Constants.MapBlockSize) {
                                Profiler.EndSample ();

                                Profiler.EndSample ();
                                return;
                        }
                        Profiler.EndSample ();

                        if (array != null) {
                                Log.Error ($"Map image tile {_fileName} has been corrupted, recreating tile");
                        }

                        if (blockMap.format != Constants.DefaultTextureFormat || blockMap.height != Constants.MapBlockSize ||
                            blockMap.width != Constants.MapBlockSize) {
                                blockMap.Reinitialize (Constants.MapBlockSize, Constants.MapBlockSize, Constants.DefaultTextureFormat,
                                        false);
                        }

                        blockMap.LoadRawTextureData (emptyImageData);

                        Profiler.EndSample ();
                }

                private void saveTextureToFile () {
                        Profiler.BeginSample ("EncodePNG");
                        byte[] array = blockMap.EncodeToPNG ();
                        Profiler.EndSample ();

                        cache.SaveTile (zoomLevel, array);
                }
        }
}