A Map Processing package for ROS

Description

This is a ROS package for map processing. It is used to process the map image file or ROS map topic.

The package currently includes:

• [space volume calculator] (src/calculate_space.cpp): calculate the space volume by extract the acceptable area in the map

The pipelines of each part above will be introduced in the following.

Details

Space volume calculator

• Aim

To calculate the area and volume by segmenting the map generated by SLAM.

• Pipelines

  • Input map

    

  • Median blur

    Use cv::medianBlur to smooth the image, remove small holes and measurement errors.

    

  • Threshold

    Use cv::inRange to keep freespace and obstacles.

    

  • Morphology operation: open

    Use cv::morphologyEx with cv::MORPH_OPEN to ignore seperated freespace.

    

  • Morphology operation: close

    Use cv::morphologyEx with cv::MORPH_CLOSE to fill holes.

    

  • Find contour

    Use cv::findContours with cv::RETR_TREE to find all contours. Then traverse all the contours to find the largest one by cv::contourArea.

    

  • Decide possible freespace

    Use cv::approxPolyDP to fit the largest contour. Then generate the space by cv::fillPoly.

    

  • Exclude non-accessible area

    Use cv::drawContours to fill those contours larger than the INNER_AREA_THRESH.

    

  • Calculate area and volume

    Traverse the freespace image to count the green pixels. Then calculate the space area and volume with the given RESOLUTION of the map and the argument floor_height.

  • Show merged results

    Use cv::addWeighted to add freespace image to the map.