Originally Posted by yash101 (Post 1319454)

Other than that, what webcam should I persuade either my parents or my team to buy? I don't think my laptop's integrated camera will cut it ;)
Thanks ;)

Originally Posted by Jerry Ballard (Post 1319985)

Last year we were sucessful using cheap Logitech webcams (C110 or C210) that you can find at a bigbox store for about $20. Since they are cheap and have been available for a long time, the Linux device drivers for these are fairly robust.

Originally Posted by Patrick Shainin (Post 1319967)

Here's a Python 'tutorial' I put together to help our team better understand the algorithm described in the FIRST vision processing doc @ http://wpilib.screenstepslive.com/s/3120/m/8731, and the similar team 341 posted vision code.

Maybe you will find it helpful if you aren't past this point yet.

https://github.com/LiftingSea/frc_vision_tutorial

It also leveraged some of the OpenCV tutorials to open multiple windows for the various stages of the processing, and provide some knobs for experimenting with tuning the algorithm in real time.

I started writing it in C++ using just the open source gcc compiler, and, as mentioned in another post here, decided to take advantage of the interactive and friendlier Python environment.

The 'tutorial' involves running the program and seeing how the tuning knobs affect the targeting results, as well as some suggested 'next steps' for students to take in the comments at the beginning of the file, to facilitate learning by example.

Originally Posted by RyanCahoon (Post 1319667)

The OpenCV documentation is actually rather good, and I found the example code to be pretty informative when I was learning OpenCV. I learn best by example, though, so YMMV. If you want a more edited, traditional book, there are a bunch listed here; you're probably most likely to find the O'Reilly OpenCV book (the first one listed, with the butterfly).

Once you've gone through a few examples, I'd suggest trying to solve one of the past years' challenges (or you can wait until Saturday :)). OpenCV is a large enough library that you'll get lost if you try to learn the entire thing without some sort of specific challenge to direct your efforts.

If you have access to the game elements from those years, that would obviously be the best; else I'd suggest looking for pictures on Chief Delphi (ex: Jared from 341 posted some example camera captures from the 2012 game) or on-robot camera footage off of YouTube (keepvid.com/). Just try applying some of the filters and see what happens. I'd recommend starting with smoothing operators, color-space conversions, and thresholds. From there, you can move onto contour analysis and simple shape detection using Hough transforms.

When it comes to webcams, some are slightly better than others, but in my experience they're all about the same. The real advantage to having another webcam besides the one built into your laptop is that you can easily aim it at things without having to contort yourself and your laptop into weird poses.

Originally Posted by yash101 (Post 1320029)

However, it is so detailed that I have no clue where to start. [...] It also comes down to that me (an many other novices) don't know what to learn and what to skip.
[...]
I will probably dissect the 341 code and rewrite it in C.

Originally Posted by yash101 (Post 1320029)

So far, the only thing I've been able to accomplish is finding a certain color (which didn't work too well because I didn't have a colored object to track).

Originally Posted by yash101 (Post 1320029)

Another thing I wonder about is whether to learn C, C++, Java or Python or maybe even something else.

One thing that I dislike about C is that the program will compile correctly. However, when I launch it, it will spit out just tons of fatal errors. How can I set the IDE (Visual Studio currently) to tell me that there are errors in the code? I have actually had my system hang because of a simple typo!

Originally Posted by yash101 (Post 1320029)

Anyways, so I have an OpenCV C++ installation. How do I install the Java bindings?

Originally Posted by RyanCahoon (Post 1320064)

IMO, there are basically two ways to go about learning something. 1) you can pick a corner to start nibbling at and random-walk your way outward until you cobble together enough to solve the problem you're currently working on 2) you can go about trying to learn the big picture and theory of the entire subject, and then try to figure out how that applies to your current problem.

Jared and I gave you lists of topics to get started with also as a way to try to give you some direction about where to focus initially.

If you like (1), the 341 example code and OpenCV tutorial code is a great way to start. If you like (2), either pick up one of those books (if there's nothing available in the library, then perhaps a late nondenominational winter holiday present? or can you convince your team to buy it as a resource to you and future students?) or you can check out courses on Coursera or EdX - though be warned that these will probably quickly require a decent understanding of calculus and linear algebra.



If you're going with the (1) experimentation route, I'd suggest that you define a specific project to work on sooner or later. Find a brightly-colored object around your house and try to track that - e.g. tennis balls can work well (more-so if they're newer).



I'd recommend you steer away from C and C++ if you're not already very comfortable with them. Essentially, with great power comes great responsibility, and you'll want to be able to focus your efforts on working out the computer vision problems without making it even more complicated.

As Jared says, Python's more concise syntax will allow you to iterate faster than you would in Java. Java will probably have a little better performance, though if you're mostly just calling OpenCV functions and not trying to process the pixels yourself, this is much less of a concern. Go with whatever language is most comfortable for you.



The recent versions of the Windows prebuilt binaries have included the Java bindings in opencv\build\java. I haven't used it myself, but I believe you should be able to just include the .jar file in your classpath and the path to either the x86 or x64 .dll in the library path. Something like

I believe 341 used JavaCV instead, which is another option.

Originally Posted by Patrick Shainin (Post 1320071)

It looks like the wpilib.screenstepslive links were changed when 2014 rolled in, and I don't see that same doc in the 2014 set. I'm posting it here for you. I found it helpful reading to get a handle on the generic approach I'm seeing used in other team's posted code.