c# - 调用 ReadPixels 以从系统帧缓冲区读取像素，而不是在绘图帧内。 UnityEngine.Texture2D :ReadPixels

Question

我正在尝试使用 unity 创建一个小的测试应用程序。我正在构建应用程序的一个实例并将其设置为充当主机，然后在统一编辑器中作为客户端运行另一个实例。在当前的迭代中，我有一个按钮，按下时应该截取屏幕截图，然后将该屏幕截图发送给所有客户端。但似乎没有任何效果。我遇到的最初问题是 ReadPixels 错误:

ReadPixels was called to read pixels from system frame buffer, while not inside drawing frame. UnityEngine.Texture2D:ReadPixels(Rect, Int32, Int32)
UNETChat:OnPostRender() (at Assets/Scripts/UNETChat.cs:50)
<TakeSnapshot>c__Iterator0:MoveNext() (at Assets/Scripts/UNETChat.cs:42)
UnityEngine.SetupCoroutine:InvokeMoveNext(IEnumerator, IntPtr) .

除此之外，一旦解决，我确信这里还有很多额外的工作是不合时宜的。但我才刚刚开始。感谢您的帮助!

using System.Collections;
using System.IO;
using UnityEngine;
using UnityEngine.Networking;
using UnityEngine.Networking.NetworkSystem;

public class MyMsgType
{
    public static short texture = MsgType.Highest + 1;
};

//Create a class that holds a variables to send
public class TextureMessage : MessageBase
{
    public byte[] textureBytes;
    public string message = "Test Received Message"; //Optional
}

public class UNETChat : Chat
{
    NetworkClient myClient;
    public Texture2D previewTexture;
    string messageToSend = "Screen Short Image";

    private void Start()
    {
        //if the client is also the server
        if (NetworkServer.active) 
        {
            // Register to connect event
            myClient.RegisterHandler(MsgType.Connect, OnConnected);
            // Register to texture receive event
            myClient.RegisterHandler(MyMsgType.texture, OnTextureReceive);
        }
        setupClient();
    }

    public IEnumerator TakeSnapshot(int width, int height)
    {
        yield return new WaitForSeconds(0.1F);
        Texture2D texture = new Texture2D(800, 800, TextureFormat.RGB24, true);
        texture.ReadPixels(new Rect(0, 0, 800, 800), 0, 0);
        texture.LoadRawTextureData(texture.GetRawTextureData());
        texture.Apply();

        sendTexture(texture, messageToSend);

        // gameObject.renderer.material.mainTexture = TakeSnapshot;

    }

    public void DoSendTexture()
    {
        StartCoroutine(TakeSnapshot(Screen.width, Screen.height));
    }

    // SERVER //////////////////////////

    //Call to send the Texture and a simple string message
    public void sendTexture(Texture2D texture, string message)
    {
        TextureMessage msg = new TextureMessage();

        //Convert Texture2D to byte array
        msg.textureBytes = texture.GetRawTextureData();
        msg.message = message;

        NetworkServer.SendToAll(MyMsgType.texture, msg);

        Debug.Log("Texture Sent!!");
    }

    // CLIENT //////////////////////////

    // Create a client and connect to the server port
    public void setupClient()
    {
        //Create new client
        myClient = new NetworkClient();
        //Register to connect event
        myClient.RegisterHandler(MsgType.Connect, OnConnected);
        //Register to texture receive event
        myClient.RegisterHandler(MyMsgType.texture, OnTextureReceive);
        //Connect to server
        myClient.Connect("localhost", 4444);
    }

    //Called when texture is received
    public void OnTextureReceive(NetworkMessage netMsg)
    {
        TextureMessage msg = netMsg.ReadMessage<TextureMessage>();

        //Your Received message
        string message = msg.message;
        Debug.Log("Texture Messsage " + message);

        //Your Received Texture2D
        Texture2D receivedtexture = new Texture2D(4, 4);
        receivedtexture.LoadRawTextureData(msg.textureBytes);
        receivedtexture.Apply();
    }

    public void OnConnected(NetworkMessage netMsg)
    {
        Debug.Log("Connected to server");
    }
}

Answer 1

等到当前帧结束后再截取屏幕截图或调用 Texture2D.ReadPixels 函数。这可以通过 WaitForEndOfFrame 类来完成。请注意我是如何缓存它的，以避免每次调用 TakeSnapshot 函数时都创建新对象。

WaitForEndOfFrame frameEnd = new WaitForEndOfFrame();

public IEnumerator TakeSnapshot(int width, int height)
{
    yield return frameEnd;

    Texture2D texture = new Texture2D(800, 800, TextureFormat.RGB24, true);
    texture.ReadPixels(new Rect(0, 0, 800, 800), 0, 0);
    texture.LoadRawTextureData(texture.GetRawTextureData());
    texture.Apply();
    sendTexture(texture, messageToSend);

    // gameObject.renderer.material.mainTexture = TakeSnapshot;
}

---

我注意到您的脚本中有 yield return new WaitForSeconds(0.1F)，它在截屏前等待 0.2 秒。如果您必须等待 0.2 秒，则先等待 0.2 秒，然后在截屏之前等待帧结束:

WaitForSeconds waitTime = new WaitForSeconds(0.1F);
WaitForEndOfFrame frameEnd = new WaitForEndOfFrame();

public IEnumerator TakeSnapshot(int width, int height)
{
    yield return waitTime;
    yield return frameEnd;

    Texture2D texture = new Texture2D(800, 800, TextureFormat.RGB24, true);
    texture.ReadPixels(new Rect(0, 0, 800, 800), 0, 0);
    texture.LoadRawTextureData(texture.GetRawTextureData());
    texture.Apply();
    sendTexture(texture, messageToSend);

    // gameObject.renderer.material.mainTexture = TakeSnapshot;
}