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一只有理想的羊驼

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Unity3D中，我需要从C++的DLL中获取摄像头取得的图像数据(uchar *)，并且用Rawimage显示出来。

程序包括C++的DLL接口部分和Unity3D C#的接口部分。

使用VS 2015建立一个空白的Visual C++ Win32控制台应用程序，使用.NET Framework 4.7.2，应用程序类型为DLL。

C++ CameraDll.cpp:

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#include "Camera.h"

#define DLLExport __declspec(dllexport)

extern "C" {
	DLLExport Camera* CreateCamera(int width, int height, int fps) {
		Camera* obj = new Camera(width, height, fps);
		return obj;
	}

	DLLExport void DestroyCamera(Camera* obj) {
		delete obj;
		obj = NULL;
	}

	DLLExport bool GetImage(Camera* obj, unsigned char *& data, int &size) {
		return obj->GetImage(data, size);
	}
}

C++ Camera.cpp:

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...
bool Camera::GetImage(unsigned char*& rgb24_pixels, int& size) {
	...
	rgb24_pixels = img.data;
	size = img.cols * img.rows * img.channels();
	return true;
}
...

编译Release x64后，将dll文件放到Unity项目的Assets\Plugins文件夹中。Unity中建立Create Empty对象，添加一个脚本Camera.cs。

C# Camera.cs

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using System;
using System.Collections;
using System.Collections.Generic;
using System.IO;
using UnityEngine;
using UnityEngine.UI;
using System.Runtime.InteropServices;

public class Camera : MonoBehaviour
{
    [DllImport("Camera")]
    private static extern IntPtr CreateCamera(int width, int height, int fps);

    [DllImport("Camera")]
    private static extern void DestroyCamera(IntPtr obj);

    [DllImport("Camera")]
    private static extern bool GetImage(IntPtr obj, ref IntPtr data, ref int size);
    
    private int width_ = 640;
    private int height_ = 480;
    private int fps_ = 30;
    
    private IntPtr Camera_ = IntPtr.Zero;
    private IntPtr data_ = IntPtr.Zero;
    private int size_ = 0;
    private byte[] buffer_ = null;

    private RawImage background_ = null;
    private Texture2D tex_ = null;

    // Start is called before the first frame update
    void Start()
    {
    	background_ = GameObject.FindWithTag("BackgroundImage").GetComponent<RawImage>(); 

    	Camera_ = CreateCamera(width_, height_, fps_);
    }

    void OnDestroy()
    {
    	if (Camera_ != IntPtr.Zero)
    	{
    		DestroyCamera(Camera_);
    		Camera_ = IntPtr.Zero;
    	}
    }

    // Update is called once per frame
    void Update()
    {
    	if (Camera_ == IntPtr.Zero) return;

    	bool flag = GetImage(Camera_, ref data_, ref size_);

    	if (!flag || size_ <= 0) return;

    	if (buffer_ == null) {
    		buffer_ = new byte[size_];
    	}

    	if (tex_ == null) {
    		tex_ = new Texture2D(width_, height_, TextureFormat.RGB24, false, false);
    	}

		System.Runtime.InteropServices.Marshal.Copy(data_, buffer_, 0, size_);
		tex_.LoadRawTextureData(buffer_);
		tex_.Apply();

		background_.texture = tex_;

		// byte[] bytes = tex_.EncodeToPNG();
		// File.WriteAllBytes("Image.png", bytes);
    }
}

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使用BestHttp的Websocket接收Binary图片数据时，发现接收一段时间后程序会卡掉，怀疑是buffer size太小。

修改/Assets/Best HTTP (Pro)/BestHTTP/Extensions/ReadOnlyBufferedStream.cs 中的READBUFFER值，改为：

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public const int READBUFFER = 81920;

问题解决。

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本文主要参考博客Unity3D 与 Python 的 Socket 通信简单指南。

Unity3D Client端

Unity3D新建一个Project，Window - Asset Store，搜索Socket.IO for Unity进行安装。Import成功后，Project目录Assets中会出现SocketIO文档。

Project目录中选择Assets - SoketIO - Prefabs，将该目录下的SocketIO拖入到场景中，如下图所示：

检查场景中SocketIO的Url属性：

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ws://127.0.0.1:4567/socket.io/?EIO=4&transport=websocket

在SampleScene栏目中右键，Create Empty建立一个空白的Object，命名为TestSocket。选择TestSocket，在Inspector窗口中点击Add Component - New script，命名为TestSocketScript，双击脚本进行编辑：

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using System.Collections.Generic;
using UnityEngine;
using SocketIO;

public class TestSocketScript : MonoBehaviour
{
    // 在 Editor 里把 SocketIO 拖过来
    public SocketIOComponent sio;
    void Start()
    {
        if (sio == null)
            Debug.LogError("Drop a SocketIOComponent to Me!");
        // 声明 connect 事件和 server_sent 事件的回调函数
        sio.On("connect", OnConnect);
        sio.On("server_sent", OnReceive);
    }
    
    /// <summary>
    /// connect 事件的回调函数
    /// </summary>
    /// <param name="obj"></param>
    void OnConnect(SocketIOEvent obj)
    {
        Debug.Log("Connection Open");
        OnReceive(obj);
    }
    
    /// <summary>
    /// 接收到 server_sent 事件的回调函数
    /// </summary>
    /// <param name="obj">SocketIOEvent</param>
    void OnReceive(SocketIOEvent obj)
    {
        // 1. 接收并输出 Server 传递过来的数字
        JSONObject jsonObject = obj.data;
        string rcv_nbr = jsonObject.GetField("nbr").str;
        Debug.Log("Recieved From Server : " + rcv_nbr);
        // 2. 将数字 +1 并返回给 Server
        try
        {
            int int_nbr = int.Parse(rcv_nbr);
            SendToServer(int_nbr + 1);
        }
        catch
        {
        }
    }
    
    /// <summary>
    /// 将数字发给 Server
    /// </summary>
    /// <param name="_nbr">发送的数字</param>
    void SendToServer(int _nbr)
    {
        Dictionary<string, string> data = new Dictionary<string, string>();
        data["nbr"] = _nbr.ToString();
        sio.Emit("client_sent", new JSONObject(data));
    }
}

此时Inspector窗口的Test Socket Script(Script)中会新增一个Sio属性：

sio1

将SampleScene栏目的SocketIO拖动到Sio属性里：

sio2

Python版Server端

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sudo pip2 install python-socketio
sudo pip2 install eventlet
sudo pip2 install Flask
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import socketio
import eventlet
import eventlet.wsgi
from flask import Flask

sio = socketio.Server()
app = Flask(__name__)

# "连接建立的回调函数"
@sio.on('connect')
def on_connect(sid, environ):    
    print("connect ", sid)
    send_to_client(101)

# "接收 Client 事件 (client_sent) 的回调函数"
@sio.on('client_sent')
def on_revieve(sid, data):    
    if data:
        print ('From Client : %s' % data['nbr'])
        send_to_client(int(data['nbr']) + 1)
    else:
        print ('Recieved Empty Data!')

# "向 Client 发送数字"
def send_to_client(_nbr):    
    sio.emit(
        'server_sent', 
        data = {'nbr':_nbr.__str__()}, 
        skip_sid=True)
      
if __name__ == '__main__':
    app = socketio.Middleware(sio, app)
    eventlet.wsgi.server(eventlet.listen(('', 4567)), app)

先运行Python程序，再运行Unity3D场景：

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