Calum Knott

I'm currently employed by Didactic Services, a FESTO Partner, as a Senior Applications Engineer.
I'm currently the WorldSkillsUK Mechatronics Training Manager
I'm also a Visiting Lecturer at Middlesex University
Occasionally I can be persuaded to Freelance!

Contact Me

These posts are archived
They were written with an old blogging platform, and are no longer really maintainable, however as they are linked too from various pages on the web - it seemed a good idea to try and archive them. I have written just enough code to get them to display - but there will probably be a few broken links and images.
Any major queries - feel free to contact me

Dissertation - Python and OpenCV - Creating a GUI

16 / 3 / 2014


So the reason I chose to write this post was I recently decided to make a GUI for the screen on the baxter robot. (see my previous posts) So I wrote a little framework for baxter that allows us to quickly create GUI's Ill put the download link at the bottom (Trust me you want to read the post before you download it) Now. I am only just getting into python so I am sure that there are many many errors with my python code. Its buggy, probably resource intesive, and I know for a fact that there is one bit that is just plain horrible. BUT!. With that in mind, I leave it open to the comments to correct my mistakes please! First and formost a little video for you all. I know you all like these so here we go:

DISCLAIMER: The design is fairly simple and is borrowed off a similar GUI I saw when the robot was demonstrated to me several months ago, by the UK supplier. I believe it is a GUI they custom coded. However after a fair bit of searching I could find anything about it online or anything comparible, and so BaxUI was born

How does BaxUI work?

Essentially I have written 2 versions of BaxUI. One is generic and has no ROS bindings or callbacks of any kind. Its it is simply a python script that draws an openCV window. that you can control with the keyboard. The second is identical, but comes with the ROS Bindings and hooks into ONE of the Baxters "navigators" (the buttons on the arms). and allows you to control it on the baxters face. NO GUI IS DISPLAYED ON THE COMPUTER IN THIS MODE. To include it in your project, simply call "import BaxUI" - for the Baxter mode, or "import BaxUI_S" - for standalone mode For the purpose of this walkthrough, Im going to keep it generic and explain the standalone mode, and the baxter mode should be an obvious extention of this.

Show me a simple example of how to generate a menu calum!

Ok, since you asked so niceley:

Thats it! three lines of code will generate this lovely menu system!

You can use the arrow keys (UP & DOWN) to 'scroll' through the options, you can use enter to select a menu option If you have more than 4 options, they will appear on the right too. 8 is the MAXIMUM number of options.

Ok great, but how do I make this menu do anything?….

Good question. Like this:

Hopefully you can tell from that snippet that when you select the second menu option, the words "I just got told to do something" have been printed to the console. Its a fairly obvious call. But you could of course launch somehting more complex:

note:: That is a crude way of doing it and "blocks" the UI while the is running. But its only a suggestion.

Did someone say "submenus"?….

YES!! submenus are equally easy to impliment: To enter a submenu, press enter, as you would to run a function. To go back up a level, press the backspace key.

Did someone say "option menus"?….

I havent totally decided if this is usefull or not, but I added the option to set variables using the GUI. Its probably quiker to hardcode this stuff, but you never know people might find a use for it. The following example shows how on the first page we could have a menu item called "print name". This would print the robots 'name' variable to the terminal. EG: "Baxter" By adding an option selector, we can toggle the name between "Bertie" or "Baxter" and then return to the main menu, and print it.

The Baxter version

The baxter version is identical in nearly every way, except that it uses the navigator instead of the keyboard. Currently I've only coded it for the right hand navigator. I should expand it really, I might post an update durin the week. ALSO. owing to a weird problem i cant seem to solve in the translation between cv2 (OpenCV) and the cv/cv_bridge to ros, it currently writes to file every time the screen updates. This is not a huge problem as the screen only updates when there is a user input, but it does mean that if a user scrolls through a list, then a file is generated, and read-back maybe 6 or 7 times. Its not ideal, but it works. I would love someone to solve it for me!


This software was never really intended for public use. It works, and i have had no problems with it, but it is quite memory intensive, and not "clean code". Use at your own risk! Oh, and its licensed GPL v2 Other (more permissive) licensing is available, please contact me for more information

Downloads etc

ALL contributions are welcome, just leave me a message in the comments! Now thats out the way! here is the code:


This contains: , , & bg.png Download Here :)

The Simple version - NOT BUILT FOR ROS/BAXTER:

The ROS/BAXTER version: