Keep/Delete OpenCV dependency

[Arpafaucon]

Description

I was doing a full installation test to list dependencies for my project.
It seems that the full OPENCV library is required. However the library usage seem quite small.

find_package(OpenCV REQUIRED)

Current usage

It seems to be used for scaling some measures, but given the TODO message, I'm not sure something is happening.

if (_sdf->HasElement("covarianceImage")) {
    std::string image_name =
      _sdf->GetElement("covarianceImage")->Get<std::string>();
    covariance_image_ = cv::imread(image_name, CV_LOAD_IMAGE_GRAYSCALE);
    if (covariance_image_.data == NULL)
      gzerr << "loading covariance image " << image_name << " failed"
            << std::endl;
    else
      gzlog << "loading covariance image " << image_name << " successful"
            << std::endl;
  }
// ...
// This gets called by the world update start event.
void
GazeboOdometryPlugin::OnUpdate(const common::UpdateInfo& _info)
{
// ...
int x =
      static_cast<int>(std::floor(gazebo_pos_x / covariance_image_scale_)) +
      width / 2;
    int y =
      static_cast<int>(std::floor(gazebo_pos_y / covariance_image_scale_)) +
      height / 2;

    if (x >= 0 && x < width && y >= 0 && y < height) {
      uint8_t pixel_value = covariance_image_.at<uint8_t>(y, x);
      if (pixel_value == 0) {
        publish_odometry = false;
        // TODO: covariance scaling, according to the intensity values could be
        // implemented here.
      }
  }
// ...
}

Propositions

At least, this issue will remind you of this waiting TODO. 😄

• If this is feature you actually use, would it be possible to define what opencv modules are required ?
• If this is a left-over, would you consider removing the dependency to openCV2 ? This will become increasingly difficult to satisfy.

[wuwushrek]

hahaha yes OpenCV is no need here ! I had it because of some rotorS dependencies that I removed.
I'm going to remove it in the next commit/push., after solving some of the other issue you pointed.