OpenCV Reinstalled on Computer Phosphene

One of the things I needed to do a few months ago, was a complete reinstall of software on a computer which was named ‘Phoenix’, but which had suffered from a hard-drive controller failure, so that it needed to be resurrected as the computer ‘Phosphene’. Both times that hardware had Debian / Stretch installed, even though the first time it was not an official Kanotix install. The second time it was.

When I need to reinstall the O/S, I also need to install much software again. And one piece of software which I’ve been focusing on somewhat in recent days, is “OpenCV“.

‘OpenCV’ is a library and a series of header files, and a set of Python modules, and a Java Interface, that specialize in Computer Vision, which could therefore be classified as a rudimentary AI, although it should be said that This form of AI is still of such a variety, that the computer is only performing remarkably complicated calculations, to be able to do things, which were not feasible only a few decades ago. It provides Image Recognition. Because of the way I am, I value having many computing resources installed, even if I rarely use them. OpenCV would be one such resource.

What tends to happen on Debian-based platforms, is that the version of OpenCV available from the package manager is a somewhat old version – in the case of Debian / Stretch, v2.4.9 – which is only important to install the library packages for, not the ‘-dev’ packages, and the former because the library packages are also dependencies of many other packages, which use OpenCV in the background, but not in any way that the user would want to write his own applications with.

What I additionally did, was to install v4.1 from the OpenCV Web-site, from source-code, and this seems like a good move because v4.1 is rumoured to be easier to write programs with, than v3.2 was, especially if the power-user does not want to end up shoulder-high in low-level code, to do many of the uninteresting parts of what his application needs to do, to be user-friendly.

But then, before writing our own applications with OpenCV, what we might also want is a demo program, that just shows users what the capabilities of this library and of this SDK are. And so the main program to do this with is called “OpenCV Demonstrator“. This could be a way to intrigue ourselves, as well to show off what our computers can do, maybe to friends?




But here I ran into a bit of a snag. ‘OpenCV Demonstrator’ has only been compiled, by its author, as an application that uses OpenCV 3.2, and according to examination of my blog entries from before the reinstall, was compatible with v3.4. It’s not compatible with v4.1, even though v4.1 is more powerful. Whenever there is a major version update, let’s say from 3 to 4, applications built against one version will no longer run, when compiled against the next version. But I wanted that Demonstration Program. And so the following is what I did:

Continue reading OpenCV Reinstalled on Computer Phosphene

I’ve just custom-compiled OpenCV.

One trend in computing is AI, and a subject related to AI, is Computer Image Recognition, which could also be called ‘Computer Vision’. And there exists an Open-Source library for that, called ‘OpenCV‘. While I tend to think of it mainly as a Linux thing, it’s also possible to download and install OpenCV on Windows.

The version of OpenCV which Linux users obtain from the package manager, tends to be an outdated version, which under Debian / Stretch, is version 2.4.9 . I have a Debian / Stretch, Debian 9 computer I name ‘Plato’, and its hardware is decently strong. But one thing I just wanted to do, was to install a more up-to-date version of OpenCV on it, that being version 3.4.2 . The way to do this under Linux, is to custom-compile. And so doing that was an overnight project this morning.

One drawback to using OpenCV remains, that it does not seem to have many working applications out-of-the-box. It offers an API, and one needs to be a very good C++ programmer, to make any use of that API. But interestingly enough, there is a demonstration application these days, called “OpenCV Demonstrator“. If one has the appropriate version of OpenCV installed, one can also custom-compile the Demonstrator.


I made some observations about these two projects the hard way this morning.

Continue reading I’ve just custom-compiled OpenCV.