【Unity】Texture2D 转Sprite 失色问题

有一个很恶心的需求就是打包后，要动态换图片，而且这个项目版本已经没有编辑器版本，只能从打包后的StreamingAssets 中读一个图片，到UI中

因为是打包以后，如果不通过反编译的话 只能去访问StreamingAssets 去加载一个图片

private Image mainBg;
mainBg = GetComponent();
        var asset = ResourceMgr.Inst.LoadAssetAsStream("RoleIMG.jpg");
        Texture2D texture = new Texture2D(asset.texture.width, asset.texture.height);
        asset.LoadImageIntoTexture(texture);
        mainBg.sprite = Sprite.Create(texture, new Rect(0, 0, texture.width, texture.height), Vector2.zero);

ResourceMgr 是自己封的一个读取类 结尾可以给出，用到了类中 LoadAssetAsStream 

 public WWW LoadAssetAsStream(string name, bool isCache = true)
    {
        if (_resourceTable.Contains(name))
            return _resourceTable[name] as WWW;
        var www = new WWW("file:///" + Path.Combine(_streamPath, name));
        Debug.Log(Path.Combine(_streamPath, name));
        while (!www.isDone) {}
        return www;
    }

返回一个www,这里会生成一个 Texture2D，然后用返回的www 这个值去调用api LoadImageIntoTexture（）

这里为什么生成一个Texture2D，如果不生成直接用 www.texture 会产生失色，根据强哥说是Mipmap问题，具体原因如果有小伙伴得知 希望给出。

失色图：

最终效果图：

最后用：

Sprite.Create去生成 sprite 赋给 定义的 image 即可

 mainBg.sprite = Sprite.Create(texture, new Rect(0, 0, texture.width, texture.height), Vector2.zero);

附上ResourceMgr 读取类

using System.Collections;
using System.IO;
using UnityEngine;



#region Modify (修改，或者新增了功能请在此进行记录（name、todo 、time）！谢谢)
#endregion
//using Object = UnityEngine.Object;
public class ResourceMgr 
{
    #region Instance

    private static ResourceMgr _inst;

    public static ResourceMgr Inst
    {
        get { return _inst = _inst ?? new ResourceMgr(); }
    }

    #endregion

    private ResourceMgr()
    {
        Init();
    }

    private string _streamPath;
    private Hashtable _resourceTable; //缓存从Resource中加载的资源

    private void Init()
    {
        _resourceTable = new Hashtable();
        _streamPath = Application.streamingAssetsPath;
    }   
   
    public T LoadAsset(string path, bool isCache = true) where T : Object
    {
        if (_resourceTable.Contains(path))
            return _resourceTable[path] as T;
        var assets = Resources.Load(path);
        if (assets == null)
        {
            Debug.LogFormat(" assets is not found at Path:{0}", path);
            return null;
        }
        if (isCache)
            _resourceTable.Add(path, assets);

        return assets;
    }

    public WWW LoadAssetAsStream(string name, bool isCache = true)
    {
        if (_resourceTable.Contains(name))
            return _resourceTable[name] as WWW;
        var www = new WWW("file:///" + Path.Combine(_streamPath, name));
        Debug.Log(Path.Combine(_streamPath, name));
        while (!www.isDone) {}
        return www;
    }

    public T InstantiateAsset(string path) where T:Object
    {
        var obj = LoadAsset(path);
        var go = GameObject.Instantiate(obj);
        if (go == null)
            Debug.LogError("Instantiate {0} failed!", obj);
        return go;
    }

    public void ClearAssetsCache()
    {
        foreach (Object asset in _resourceTable)
        {
#if UNITY_EDITOR
            GameObject.DestroyImmediate(asset, true);
#else
            GameObject.DestroyObject(asset);
#endif
        }
        _resourceTable.Clear();
    }
}