A discussion about SDK design

[Euraxluo]

Why not refer to the Ros SDK? I find that the two are quite different。

ROS style(and other message queue) like that:

#include "dora.h" 
#include "opencv2/opencv.hpp" 
#include "sensor_msgs/Image.h"
#include "std_msgs/String.h"


cv::Mat g_image;
std::vector<cv::Rect> g_bboxes;

// callback for topic 1
void image_callback(const sensor_msgs::Image::SharedPtr image_msg)
{
    printf("Received image message\n");


    cv_bridge::CvImagePtr cv_ptr;
    try
    {
        cv_ptr = cv_bridge::toCvCopy(image_msg, sensor_msgs::image_encodings::BGR8);
    }
    catch (cv_bridge::Exception& e)
    {
        ROS_ERROR("cv_bridge exception: %s", e.what());
        return;
    }

    g_image = cv_ptr->image;
}

// callback for topic 2
void bbox_callback(const std_msgs::String::SharedPtr bbox_msg)
{
    printf("Received bbox message\n");


    // {"bboxes": [{"x": 100, "y": 200, "w": 50, "h": 50}, {"x": 300, "y": 400, "w": 100, "h": 100}]}
    std::string json_str = bbox_msg->data;
    ...
}

// build publish data
void image_overlay()
{

    if (!g_image.empty() && !g_bboxes.empty())
    {
        cv::Mat overlay_image = g_image.clone();

        for (int i = 0; i < g_bboxes.size(); i++)
        {
            cv::Rect bbox = g_bboxes[i];
            cv::rectangle(overlay_image, bbox, cv::Scalar(0, 255, 0), 2);
        }
        ...
    }
}

int main(int argc, char** argv)
{
     auto node  = dora_init(***);  // init 

    /// may that can auto deserialization or not
    auto image_subscriber = node->create_subscription<sensor_msgs::Image>("image_topic", image_callback);
    auto bbox_subscriber = node->create_subscription<std_msgs::String>("bbox_topic", bbox_callback);

    // create pub
    auto overlayed_image_publisher = node->create_publisher<sensor_msgs::Image>("overlayed_image_topic", 10);

    // maybe need?
    dora::Rate loop_rate(10);

    while (dora::ok())// or other check node status
    {
        // do something
        image_overlay();

        // TODO:  publish image
        ...


        dora::spin_some(node);
        loop_rate.sleep();
    }

    dora::shutdown();
    return 0;
}

I've been looking at Dora's history, and I see that it's been designed this way since very early times

[haixuanTao]

Hi Euraxluo,

Could you be more specific about which exact SDK from ROS, you would want to see?

Is it the callback design? I think that with the current on_event, you should get pretty close?

Or is it the publishing loop?

[Euraxluo]

i just want to know the SDK design idea.
In terms of functional implementation alone, both designs can achieve the desired goal。