ROS & Ubuntu Tips

Here are some personal tips for using ROS. After I realized I kept googling the same basic information.

1. Clone existing package from GitHub

• Create and build a workspace

  $ mkdir -p ~/xxx_ws/src
  $ cd ~/xxx_ws/
  $ catkin_make
  

• Clone package

  $ cd ~/xxx_ws/src
  $ git clone https://xxxxxx.git
  $ cd ~/xxx_ws/
  $ catkin_make
  

  Keep in mind that your workspace has a tree like this:

|/home
├── /usr
│   ├── /xxx_ws
│   │   ├── /build
│   │   ├── /devel
│   │   ├── /src
│   │   |   ├── /your_cloned_package
│   │   |   ├── /your_other_package

2. Create a virtual environment

Python virtual environments can create an isolated environment for different Python projects. Thus, a specific version of a module on a project basis installation won’t affect other Python projects. Here is a step by step instructions about how to create Python virtual environments on Ubuntu 18.04.

1. update all packages

      $ apt-get update -y
   

2. install the python3-venv package

      $ sudo apt install python3-venv
   

3. Create a folder (my folder name: virenv) for the virtual environment

      $ mkdir virenv
      $ cd virenv
   

4. Create and activate the virtual environment (my environment name: gpflow)

      $ python3 -m venv gpflow 
      $ source gpflow/bin/activate
   

5. Install jupyter notebook and add the virtualenv (gpflow) as a jupyter kernel

      $ pip install jupyterlab
      $ pip install ipykernel
      $ python -m ipykernel install --name gpflow --user
   

   In the opened notebook, navigate to Kernel, then Change kernel, pick gpflow.

3. Image & video processing by ffmpeg

1. Convert video format

      $ ffmpeg -i input.mov -qscale 0 output.mp4
   

2. Combine images to video:

      $ ffmpeg -framerate 5 -i img-%02d.png video.avi
      $ ffmpeg -framerate 30 -i %07d.jpg video.avi
      $ ffmpeg -framerate 30 -s 1280x960 -pattern_type glob -i '*.png' -crf 15 test.mp4
   

3. Cut video

      $ ffmpeg -i DJI_0004.MOV -ss 00:00:00 -to 00:03:20 -c:v copy -c:a copy output.MOV
   

4. Extract images from videos

      $ ffmpeg -i input.mp4 -qscale:v 2 output_%03d.jpg
   

5. Resize image

      $ ffmpeg -i input.jpg -vf scale=2048:1024 output.png
   

4. Adjust Ubuntu screen resolution

   $ xrandr
   $ xrandr -s 1920*1200

5. Install and uninstall Visual Studio

Install

1. install the repository and key

      $ wget -qO- https://packages.microsoft.com/keys/microsoft.asc | gpg --dearmor > packages.microsoft.gpg
      $ sudo install -o root -g root -m 644 packages.microsoft.gpg /etc/apt/trusted.gpg.d/
      $ sudo sh -c 'echo "deb [arch=amd64 signed-by=/etc/apt/trusted.gpg.d/packages.microsoft.gpg] https://packages.microsoft.com/repos/vscode stable main" > /etc/apt/sources.list.d/vscode.list'
   

2. update the package cache and install the package

      $ sudo apt-get install apt-transport-https
      $ sudo apt-get update
      $ sudo apt-get install code
   

   Uninstall

3. uninstall

      $ sudo apt-get purge code
   

4. remove settings

      $ cd ~ && rm -rf .vscode && rm -rf .config/Code