Hello everyone, I am a computer vision developer working for a startup which aims to make a wall-painting robot and am utilizing a double OAK-1 Lite W camera setup for obstacle detection. As a ROS newbie I need help implementing a custom pipeline for the ROS driver. I wanted to setup the pipeline which only publishes a grayscale image to improve the performance, but am having issues when launching the camera driver saying the plugin failed to load because the loaded plugin description does not exist.

I have the depthai ros packages installed using sudo apt install ros-humble-depthai-ros

As explained in the official documentation and the pipelines section, I have created a package called "custom plugins", created a header and source file containing the class derived from the BasePipeline class and have overridden the createPipeline method and exported it using PLUGINLIB_EXPORTCLASS function, followed by creating a plugins.xml and including a plugin description for the class. Finally, I have modified the i_pipeline_type to point to my plugins::GrayscalePipeline but no luck.

Below I am including the contents of the files to reproduce the error. Keep in mind the createPipeline method is the same as the createPipeline method of the RGB pipeline type since I wanted to first make sure my plugin creation works.

depthai_grayscale_plugin.hpp

#include <memory>
#include <vector>


#include "rclcpp/rclcpp.hpp"
#include "depthai_ros_driver/dai_nodes/base_node.hpp"
#include "depthai_ros_driver/pipeline/base_pipeline.hpp"

namespace plugins
{
    class GrayscalePipeline : public depthai_ros_driver::pipeline_gen::BasePipeline
    {
    public:
        std::vector<std::unique_ptr<depthai_ros_driver::dai_nodes::BaseNode>> createPipeline(
            rclcpp::Node* node,
            std::shared_ptr<dai::Device> device,
            std::shared_ptr<dai::Pipeline> pipeline,
            const std::string& nnType) override;
    };
}

depthai_grayscale_plugin.cpp

#include <memory>

#include "depthai_ros_driver/dai_nodes/sensors/sensor_wrapper.hpp"
#include "depthai_ros_driver/utils.hpp"

#include "depthai_grayscale_plugin.hpp"

std::vector<std::unique_ptr<depthai_ros_driver::dai_nodes::BaseNode>> plugins::GrayscalePipeline::createPipeline(
    rclcpp::Node * node, std::shared_ptr<dai::Device> device, std::shared_ptr<dai::Pipeline> pipeline, const std::string & nnType)
{
    auto nType = depthai_ros_driver::utils::getValFromMap(nnType, nnTypeMap);

    std::vector<std::unique_ptr<depthai_ros_driver::dai_nodes::BaseNode>> daiNodes;

    auto gray = std::make_unique<depthai_ros_driver::dai_nodes::SensorWrapper>("rgb", node, pipeline, device, dai::CameraBoardSocket::CAM_A);

    daiNodes.push_back(std::move(gray));

    return daiNodes;
}

#include "pluginlib/class_list_macros.hpp"
PLUGINLIB_EXPORT_CLASS(plugins::GrayscalePipeline, depthai_ros_driver::pipeline_gen::BasePipeline)

CMakeLists.txt

cmake_minimum_required(VERSION 3.8)
project(custom_plugins)

if(CMAKE_COMPILER_IS_GNUCXX OR CMAKE_CXX_COMPILER_ID MATCHES "Clang")
  add_compile_options(-Wall -Wextra -Wpedantic)
endif()

# find dependencies
find_package(ament_cmake REQUIRED)
find_package(pluginlib REQUIRED)
find_package(depthai_ros_driver REQUIRED)
# uncomment the following section in order to fill in
# further dependencies manually.
# find_package(<dependency> REQUIRED)

add_library(custom_plugins include/custom_plugins/depthai_grayscale_plugin.hpp src/depthai_grayscale_plugin.cpp)

target_include_directories(custom_plugins PUBLIC  
    $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include/custom_plugins>  
    $<INSTALL_INTERFACE:include/custom_plugins>  # <prefix>/include/mylib
)

ament_target_dependencies(
  custom_plugins
  depthai_ros_driver
  pluginlib
)

pluginlib_export_plugin_description_file(depthai_ros_driver plugins.xml)

install(
  TARGETS custom_plugins
  EXPORT export_${PROJECT_NAME}
  ARCHIVE DESTINATION lib
  LIBRARY DESTINATION lib
  RUNTIME DESTINATION bin
)

ament_export_libraries(
  custom_plugins
)
ament_export_targets(
  export_${PROJECT_NAME}
)

ament_package()

plugins.xml

<library path="custom_plugins">
    <class type="plugins::GrayscalePipeline" base_class_type="depthai_ros_driver::pipeline_gen::BasePipeline">
        <description>Grayscale Pipeline.</description>
    </class>
</library>

package.xml

<?xml version="1.0"?>
<?xml-model href="http://download.ros.org/schema/package_format3.xsd" schematypens="http://www.w3.org/2001/XMLSchema"?>
<package format="3">
  <name>custom_plugins</name>
  <version>0.0.0</version>
  <description>Package containing custom plugins</description>
  <maintainer email="spalj.grigor@gmail.com">grixi1405</maintainer>
  <license>Apache 2.0</license>

  <depend>pluginlib</depend>
  <depend>depthai_ros_driver</depend>

  <buildtool_depend>ament_cmake</buildtool_depend>

  <test_depend>ament_lint_auto</test_depend>
  <test_depend>ament_lint_common</test_depend>

  <export>
    <build_type>ament_cmake</build_type>
  </export>
</package>

Let me know if there is any more information you need. Thank you in advance