Game Player - Step 1 - Finding the Game Board

I seem to be spending a great amount of time writing blog posts and not a huge amount of time actually progressing with the program. I think this is because a lot of my time so far has been spent capturing screen shots for the setting up portion of the system so now that that is over with things should proceed a bit more briskly.

So we've got our image data in C and we also have the ability to generate a window, let's combine the two so we can see our image from C and that way we can be certain that we do in fact have our image data and not just a jumble of non-sense.

Problems Setting up 64 bit OpenCV

If you've been following the Game Player project I've been blogging about you'll know I has some trouble getting the 64 bit libraries of OpenCV to link with my project and had to stick with the 32 bit ones. Here I'll go into more details about the problem and hopefully find a solution.

First a little bit of background information on my system:

• Windows 7 Home Premium 64 bit
• OpenCV 2.4.2 pre-compiled binaries
• Netbeans 7.0.1
• Java 1.6 (not sure of bitness)
• MinGW-32 C Compiler with gcc version 4.5.2

Game Player - Step 1 - Setting Up and Using OpenCV

This is the part I hate the most because it can be fraught with errors and you can end up spending masses of time on what is essentially just setting up the environment. I don't mind spending ages on a problem when it is a problem in development or trying to work out how to solve a tricky algorithm issue but spending ages on just setting something up drives me mad. Hopefully it will go smoothly this time...

Game Player - Step 1 - Transfer BufferedImage to C

When we ended the last post we had our screen captured and stored in a Java BufferedImage object. The problem we face now is that we want to do all our reasoning inside C using OpenCV, not in Java, so we need a way to gain access to the image data from C. This is where JNI and our native methods come into play.

So far we have only defined one native method that prints a line to the screen letting us know the library has been loaded successfully. In reality we don't need to print this message as an exception will be thrown if the library doesn't load but we'll leave it in for now just for the added reassurance. We will also define another native method but this time we will pass in our newly acquired image with it. There is just one small task we want to do before hand though...

Game Player - Step 1 - Capturing the Board

Right, Step 1 in our Game Player program is capturing the game board.

This is actually an incredibly easy step so before we do that let's do a little setting up of our system's architecture. Yuk, I hate phrases like that, over complicated computing science terms are a pain in the butt and will not feature in this blog where avoidable. I'd much rather say let's get all the bits of our system in place...

As mentioned we are going to use OpenCV for all our reasoning purposes so we need a way of accessing OpenCV from Java. In order to do this we make a native library that we can call from within our Java code using the Java Native Interface (JNI). What is a native library you ask? It is code written in another language, often C, that can be called from other programs. All those .dll files in your Windows system or all those .so files in your Linux distribution are examples of native libraries and are what we are about to make. Don't worry, it's not as scary as it sounds!