source: binary-improvements2/MapRendering/Web/Handlers/ItemIconHandler.cs@ 384

using System;
using System.Collections.Generic;
using System.IO;
using System.Net;
using UnityEngine;
using HttpListenerRequest = SpaceWizards.HttpListener.HttpListenerRequest;
using HttpListenerResponse = SpaceWizards.HttpListener.HttpListenerResponse;
using Object = UnityEngine.Object;

namespace AllocsFixes.NetConnections.Servers.Web.Handlers {
        public class ItemIconHandler : AbsHandler {
                private readonly Dictionary<string, byte[]> icons = new Dictionary<string, byte[]> ();
                private readonly bool logMissingFiles;

                private bool loaded;

                static ItemIconHandler () {
                        Instance = null;
                }

                public ItemIconHandler (bool _logMissingFiles, string _moduleName = null) : base (_moduleName) {
                        logMissingFiles = _logMissingFiles;
                        Instance = this;
                }

                public static ItemIconHandler Instance { get; private set; }

                public override void HandleRequest (string _requestPath, HttpListenerRequest _req, HttpListenerResponse _resp, WebConnection _con,
                        int _permissionLevel) {
                        if (!loaded) {
                                _resp.StatusCode = (int) HttpStatusCode.InternalServerError;
                                Log.Out ("Web:IconHandler: Icons not loaded");
                                return;
                        }

                        string requestFileName = _requestPath.Remove (0, urlBasePath.Length);
                        requestFileName = requestFileName.Remove (requestFileName.LastIndexOf ('.'));

                        if (icons.ContainsKey (requestFileName) && _requestPath.EndsWith (".png", StringComparison.OrdinalIgnoreCase)) {
                                _resp.ContentType = MimeType.GetMimeType (".png");

                                byte[] itemIconData = icons [requestFileName];

                                _resp.ContentLength64 = itemIconData.Length;
                                _resp.OutputStream.Write (itemIconData, 0, itemIconData.Length);
                        } else {
                                _resp.StatusCode = (int) HttpStatusCode.NotFound;
                                if (logMissingFiles) {
                                        Log.Out ("Web:IconHandler:FileNotFound: \"" + _requestPath + "\" ");
                                }
                        }
                }

                public bool LoadIcons () {
                        
                        lock (icons) {
                                if (loaded) {
                                        return true;
                                }

                                MicroStopwatch microStopwatch = new MicroStopwatch ();

                                // Get list of used tints for all items
                                Dictionary<string, List<Color>> tintedIcons = new Dictionary<string, List<Color>> ();
                                foreach (ItemClass ic in ItemClass.list) {
                                        if (ic != null) {
                                                Color tintColor = ic.GetIconTint ();
                                                if (tintColor != Color.white) {
                                                        string name = ic.GetIconName ();
                                                        if (!tintedIcons.ContainsKey (name)) {
                                                                tintedIcons.Add (name, new List<Color> ());
                                                        }

                                                        List<Color> list = tintedIcons [name];
                                                        list.Add (tintColor);
                                                }
                                        }
                                }

                                try {
                                        loadIconsFromFolder (GameIO.GetGameDir ("Data/ItemIcons"), tintedIcons);
                                } catch (Exception e) {
                                        Log.Error ("Failed loading icons from base game");
                                        Log.Exception (e);
                                }

                                // Load icons from mods
                                foreach (Mod mod in ModManager.GetLoadedMods ()) {
                                        try {
                                                string modIconsPath = mod.Path + "/ItemIcons";
                                                loadIconsFromFolder (modIconsPath, tintedIcons);
                                        } catch (Exception e) {
                                                Log.Error ("Failed loading icons from mod " + mod.ModInfo.Name.Value);
                                                Log.Exception (e);
                                        }
                                }

                                loaded = true;
                                Log.Out ("Web:IconHandler: Icons loaded - {0} ms", microStopwatch.ElapsedMilliseconds);

                                return true;
                        }
                }

                private void loadIconsFromFolder (string _path, Dictionary<string, List<Color>> _tintedIcons) {
                        if (Directory.Exists (_path)) {
                                foreach (string file in Directory.GetFiles (_path)) {
                                        try {
                                                if (file.EndsWith (".png", StringComparison.OrdinalIgnoreCase)) {
                                                        string name = Path.GetFileNameWithoutExtension (file);
                                                        Texture2D tex = new Texture2D (1, 1, TextureFormat.ARGB32, false);
                                                        if (tex.LoadImage (File.ReadAllBytes (file))) {
                                                                AddIcon (name, tex, _tintedIcons);

                                                                Object.Destroy (tex);
                                                        }
                                                }
                                        } catch (Exception e) {
                                                Log.Exception (e);
                                        }
                                }
                        }
                }

                private void AddIcon (string _name, Texture2D _tex, Dictionary<string, List<Color>> _tintedIcons) {
                        icons [_name + "__FFFFFF"] = _tex.EncodeToPNG ();

                        if (_tintedIcons.ContainsKey (_name)) {
                                foreach (Color c in _tintedIcons [_name]) {
                                        string tintedName = _name + "__" + AllocsUtils.ColorToHex (c);
                                        if (!icons.ContainsKey (tintedName)) {
                                                Texture2D tintedTex = new Texture2D (_tex.width, _tex.height, TextureFormat.ARGB32, false);

                                                for (int x = 0; x < _tex.width; x++) {
                                                        for (int y = 0; y < _tex.height; y++) {
                                                                tintedTex.SetPixel (x, y, _tex.GetPixel (x, y) * c);
                                                        }
                                                }

                                                icons [tintedName] = tintedTex.EncodeToPNG ();

                                                Object.Destroy (tintedTex);
                                        }
                                }
                        }
                }
        }
}