unity 加载网络图片

摘要：利用Http加载网络图片。

解决思路：

1、直接用unity 自带的www加载，在高版本www已经过时了。

2、本文直接使用万能的文件流加载。

（1）使用System.Net.HttpWebRequest 请求网络流。

（2）利用System.Drawing这个dll把网络流装载到内存。可以获取远程网络图片的基本信息，图片宽高，格式等。如果已经知道远程图片数据，可以先把网络流拷贝到内存，直接对流进行操作。

（3）Texture2D.LoadImage显示图片

废话不多说，直接上代码

获取网络图片二进制数据：

public struct RemoteImageMessage
{
    public int Width;

    public int Height;

    public byte[] DataSource;
}

public static class ImageDownloadHelper
{
    /// <summary>
    /// 获取远程图片
    /// </summary>
    /// <param name="imgPath"></param>
    /// <param name="complete"></param>
    public static void GetImage(string imgPath, Action<RemoteImageMessage> complete)
    {
        System.Threading.Tasks.Task.Run(() =>
        {
            RemoteImageMessage remoteImageMessage = new RemoteImageMessage();
            try
            {
                System.Net.HttpWebRequest webRequest = System.Net.WebRequest.CreateHttp(imgPath);
                using (var response = webRequest.GetResponse())
                {
                    if (response.ContentLength != 0)
                    {
                        System.IO.Stream stream = response.GetResponseStream();
                        System.Drawing.Image image = System.Drawing.Image.FromStream(stream);
                        remoteImageMessage.Width = image.Width;
                        remoteImageMessage.Height = image.Height;
                        var bytes = ImageToBytes(image);
                        remoteImageMessage.DataSource = bytes;
                        stream.Close();
                        stream.Dispose();
                    }
                }
            }
            catch (Exception ex)
            {
                Debug.LogError("加载图片出错！" + ex);
            }
            finally
            {
                complete?.Invoke(remoteImageMessage);
            }
        });
    }

    /// <summary>
    /// Image 转bytes
    /// </summary>
    /// <param name="image"></param>
    /// <returns></returns>
    private static byte[] ImageToBytes(System.Drawing.Image image)
    {
        System.Drawing.Imaging.ImageFormat format = image.RawFormat;
        using (System.IO.MemoryStream ms = new System.IO.MemoryStream())
        {
            if (format.Equals(System.Drawing.Imaging.ImageFormat.Jpeg))
            {
                image.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
            }
            else if (format.Equals(System.Drawing.Imaging.ImageFormat.Png))
            {
                image.Save(ms, System.Drawing.Imaging.ImageFormat.Png);
            }
            else if (format.Equals(System.Drawing.Imaging.ImageFormat.Bmp))
            {
                image.Save(ms, System.Drawing.Imaging.ImageFormat.Bmp);
            }
            else if (format.Equals(System.Drawing.Imaging.ImageFormat.Gif))
            {
                image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
            }
            else if (format.Equals(System.Drawing.Imaging.ImageFormat.Icon))
            {
                image.Save(ms, System.Drawing.Imaging.ImageFormat.Icon);
            }
            byte[] buffer = new byte[ms.Length];
            //Image.Save()会改变MemoryStream的Position，需要重新Seek到Begin
            ms.Seek(0, System.IO.SeekOrigin.Begin);
            ms.Read(buffer, 0, buffer.Length);
            return buffer;
        }
    }

}

在unity中显示

public class ImageLoaderHeler : MonoBehaviour
{
    private RawImage rawImage = null;

    private string[] imageUrl = new string[]
    {   "http://t8.baidu.com/it/u=2247852322,986532796&fm=79&app=86&f=JPEG?w=1280&h=853",
        "http://t9.baidu.com/it/u=3363001160,1163944807&fm=79&app=86&f=JPEG?w=1280&h=830",
        "http://t9.baidu.com/it/u=583874135,70653437&fm=79&app=86&f=JPEG?w=3607&h=2408",
        "http://t9.baidu.com/it/u=2268908537,2815455140&fm=79&app=86&f=JPEG?w=1280&h=719",
        "http://t7.baidu.com/it/u=1179872664,290201490&fm=79&app=86&f=JPEG?w=1280&h=854",
        "http://t9.baidu.com/it/u=3923875871,1613462878&fm=79&app=86&f=JPEG?w=1280&h=854",
        "http://t9.baidu.com/it/u=3949188917,63856583&fm=79&app=86&f=JPEG?w=1280&h=875",
        "http://t7.baidu.com/it/u=1355385882,1155324943&fm=79&app=86&f=JPEG?w=1280&h=854",
        "http://t8.baidu.com/it/u=2857883419,1187496708&fm=79&app=86&f=JPEG?w=1280&h=763",
        "http://t7.baidu.com/it/u=830740827,3648735644&fm=79&app=86&f=JPEG?w=1280&h=853",
        "http://t8.baidu.com/it/u=198337120,441348595&fm=79&app=86&f=JPEG?w=1280&h=732",
        "http://t9.baidu.com/it/u=1577456063,1344044640&fm=79&app=86&f=JPEG?w=1280&h=853",
        "http://t8.baidu.com/it/u=2678662753,1297312162&fm=79&app=86&f=JPEG?w=1181&h=787",
        "http://t8.baidu.com/it/u=2148738019,2920001333&fm=79&app=86&f=JPEG?w=1181&h=788",
        "http://t9.baidu.com/it/u=1373840141,993565751&fm=79&app=86&f=JPEG?w=1181&h=788"
    };

    // Start is called before the first frame update
    void Start()
    {
        rawImage = GetComponent<RawImage>();
        //InvokeRepeating("Test", 3, 0.5f);
    }


    private int index = 0;

    private void Test()
    {
        if (index >= imageUrl.Length)
        {
            index = 0;
        }
        LoadImage(imageUrl[index++]);
    }

    private void LoadImage(string imagePath)
    {
        var start = DateTime.Now;
        Debug.LogError("图片数据开始加载！");
        ImageDownloadHelper.GetImage(imagePath, (image) =>
         {
             ThreadCrossor.GetInstance()?.AddTaskToMainThread(() =>
             {
                 var ori = rawImage.texture;
                 if (ori != null)
                 {
                     DestroyImmediate(ori);
                     rawImage.texture = null;
                 }
                 Debug.LogError($"图片尺寸{image.Width},{image.Height}");
                 Texture2D texture2D = new Texture2D(image.Width, image.Height);
                 texture2D.LoadImage(image.DataSource);
                 rawImage.texture = texture2D;
             });
             Debug.LogError($"完成图片加载！加载时间：{(DateTime.Now - start).TotalSeconds}s");
         });
    }

  
    // Update is called once per frame
    void Update()
    {
       
    }
}

写了一个简单的跨线程交互的类

public class ThreadCrossor : MonoBehaviour
{
    private static ThreadCrossor threadCrossor = null;

    List<Action> actions = new List<Action>();

    public static ThreadCrossor GetInstance()
    {
        return threadCrossor;
    }

    /// <summary>
    /// 往主进程添加任务
    /// </summary>
    /// <param name="action"></param>
    public void AddTaskToMainThread(Action action)
    {
        lock (actions)
        {
            actions.Add(action);
        }
    }

    // Start is called before the first frame update
    void Start()
    {
        threadCrossor = this;
    }

    // Update is called once per frame
    void Update()
    {
        lock (actions)
        {
            if (actions.Count > 0)
            {
                foreach(var action in actions)
                {
                    action?.Invoke();
                }
                actions.Clear();
            }
        }
    }
}

效果如下：