1. 说明

在windows10下Qt使用Lcm通讯库，以及数据传输测试，运行界面如下：
1）发送端：

2）接收端：

2. 主要代码段

1）发送端

void MainWindow::on_btn_select_clicked()
{
    QString path = QFileDialog::getOpenFileName(this, "选择 img", "./", "Image Files(*.jpg *.png *.jpeg)");
    if(path.isEmpty())
    {
        return;
    }

    QImage scaledimg;

    if(!(img.load(path))) //加载图像
    {
        QMessageBox::information(this,"failed","failed open image !");
        return;
    }
    img=img.convertToFormat(QImage::Format_RGB888);

    src_width=img.width();
    src_height=img.height();
    int scal_width=0;
    int scal_height=0;
    QString str_width,str_heigth;

    QRect originRect = ui->label_image->geometry();
    ui->label_image->setGeometry(originRect.x(),originRect.y(),400,300);
    int Mul=1;
    if(src_width/400>=src_height/300)
    {
        Mul=src_width/400;
    }
    else
    {
       Mul=src_height/300;
    }
    if(Mul>0)
    {
        scal_width=src_width/Mul;
        scal_height=src_height/Mul;
    }
    else
    {
        scal_width=src_width;
        scal_height=src_height;
    }

    scaledimg=img.scaled(scal_width,scal_height,Qt::KeepAspectRatio);


    ui->label_text->setText("src image: "+QString("width: ")+str_width.setNum(src_width)+QString(", height: ")+str_heigth.setNum(src_height));
    ui->label_image->setPixmap(QPixmap::fromImage(scaledimg));
	}


	void MainWindow::on_btn_send_clicked()
	{
	    //lcm feed msg
	    if(!mylcm.good())
	    {
	        QMessageBox::information(this,"lcm","lcm is not good!");
	        return;
	    }

    qint64 timestamp = QDateTime::currentDateTime().toMSecsSinceEpoch(); 
    std::string str_image_name;
    str_image_name=ui->lineEdit_image_name->text().toStdString();
    std::string str_channel_name;
    str_channel_name=ui->lineEdit_channel_name->text().toStdString();

    exlcm::test msg;
    msg.timestamp=timestamp;
    msg.position[0]=src_width;
    msg.position[1]=src_height;
    msg.position[2]=3;
    msg.orientation[0]=0;
    msg.orientation[1]=0;
    msg.orientation[2]=0;
    msg.orientation[3]=1;
    msg.num_datas=img.sizeInBytes();
    msg.datas.resize(msg.num_datas);
    memcpy(&msg.datas[0], img.bits(), msg.num_datas*sizeof (uchar));
    msg.name=str_image_name;
    msg.enabled=true;

    int rt = mylcm.publish(str_channel_name,&msg);
    //QMessageBox::information(this,"lcm pub",rt==0?"success":"failure");
    if(rt==0)
    {
        ui->textBrowser->append("timestamp:"+QString::number(timestamp)+" ---- success contens: channel name( "+QString::fromStdString(str_channel_name)+" ),"+
                                "image size: "+QString::number(src_width) + "*"+QString::number(src_height));
    }
    else
    {
        ui->textBrowser->append("timestamp:"+QString::number(timestamp)+" ---- failure contens: channel name( "+QString::fromStdString(str_channel_name)+" ),"+
                                "image size: "+QString::number(src_width) + "*"+QString::number(src_height));
    }
}

2）接收端

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
    , mylcm("udpm://239.255.76.67:7667?ttl=1")
{
    ui->setupUi(this);
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::on_btn_receive_clicked()
{
    QMessageBox::information(this,"btn_receive","start receive data!");
    if(!mylcm.good())
    {
        return;
    }
    mylcm.subscribe("TEST", &Handler::handleMessage, &myhandler);
    if(mylcm.handle() == 0)
    {
        uchar *datas = new uchar[myhandler.image_data.num_datas*sizeof (uchar)];
        memcpy(datas, &myhandler.image_data.datas[0],myhandler.image_data.num_datas*sizeof(uchar));
        QImage img(datas,myhandler.image_data.position[0],myhandler.image_data.position[1], QImage::Format_RGB888);
        std::string file_name = std::to_string(myhandler.image_data.timestamp)+".jpeg";
        //img.save(file_name.c_str(),"JPEG");

    QRect originRect = ui->label_image->geometry();
    ui->label_image->setGeometry(originRect.x(),originRect.y(),400,300);
    int ratio = 1;
    int src_width = myhandler.image_data.position[0];
    int src_height = myhandler.image_data.position[1];
    int scal_width,scal_height;
    if(src_width/400 >= src_height/300)
    {
        ratio = src_width/400;
    }
    else
    {
       ratio = src_height/300;
    }
    if(ratio > 0)
    {
        scal_width=src_width/ratio;
        scal_height=src_height/ratio;
    }
    else
    {
        scal_width=src_width;
        scal_height=src_height;
    }
    QImage scaledimg;
    scaledimg=img.scaled(scal_width,scal_height,Qt::KeepAspectRatio);

    QString str_width,str_heigth;
    ui->label_text->setText("receive image: "+QString("width: ")+str_width.setNum(src_width)+QString(", height: ")+str_heigth.setNum(src_height));
    ui->label_image->setPixmap(QPixmap::fromImage(scaledimg));

    delete [] datas;
	}
return;
}

3. 问题及解决

1）问题

mainwindow.obj: -1: error: LNK2019: 无法解析的外部符号 __imp__lcm_create，函数 “public: __thiscall lcm::LCM::LCM(class std::basic_string<char,struct std::char_traits,class std::allocator >)” (??0LCM@lcm@@QAE@V?

basic_string@DU?

$ba s i c_{s} t r in g @ D U ?$ char_traits@D@std@@V? $KaTeX parse error: Expected group after ‘_’ at position 78: \dots019: 无法解析的外部符号 _̲_imp__lcm_destr\dots$ basic_string@DU?