Lab07

Basic image processing task

Setup

NB: If you haven't already, install the new VM.

Take a moment to familarise yourself with symbolic links (symlinks):

https://www.digitalocean.com/community/tutorials/workflow-symbolic-links

https://linuxhandbook.com/symbolic-link-linux/

First create the new catkin workspace for this week:

mkdir -p ~/lab_workspaces/lab07_ws/src

Create the repo directory if not already created

mkdir -p ~/lab_demo_repos/
cd ~/lab_demo_repos/

Clone this repo into ~/lab_demo_repos/

git clone git@github.com:UNSW-MTRN4230-T2-2021/lab07_demo.git

Symbolically link the two packages from the repo into the lab workspace

ln -s ~/lab_demo_repos/lab07_demo/thresholding ~/lab_workspaces/lab07_ws/src
ln -s ~/lab_demo_repos/lab07_demo/aruco_detection ~/lab_workspaces/lab07_ws/src
cd ~/lab_workspaces/lab07_ws/

If you look in the ~/lab_workspaces/lab07_ws/src directory, you will find the repo is now symbolically linked into the workspace

Then create and source the necessary files

 catkin_make
 source  devel/setup.bash

• To use C++:

  roslaunch thresholding thresholding_cpp.launch
  

• To use Python:

  roslaunch thresholding thresholding_py.launch
  

Examples of image processing methods

Opening an image from file

Reading an image from a rostopic

Displaying an image

Colour space conversion

RGB --> HSV

HSV --> RGB

RGB --> LAB

RGB --> Grayscale

Thresholding

Morphology

Erosion

Dilation

Opening

Closing

Region properties - Centroids

Brightness adjustment

Histogram equalisation

Sharpen / blur

Sobel edge

Corner detection: FAST

Detectors: SURF

Descriptors

SIFT

ORB

Post lab extra: Fiducial (ArUco Marker) Detection

Tutorial on ArUco Markers To start the node (which simply executes then waits for keypress to exit)

cd ~/lab_workspaces/lab07_ws/
catkin_make
source devel/setup.bash
roslaunch aruco_detection aruco_detection.launch