Image Recognition

Question

I'd like to do some work with the nitty-gritties of computer imaging. I'm looking for a way to read single pixels of data, analyze them programatically, and change them. What is the best language to use for this (Python, c++, Java...)? What is the best fileformat?

I don't want any super fancy software/APIs... I'm looking for the bare basics.

Answer 1

If you need speed (you'll probably always want speed with image processing) you definitely have to work with raw pixel data. Java has some real disadvantages as you cannot access memory directly which makes pixel access quite slow compared to accessing the memory directly. C++ is definitely the language of choice for production use image processing. But you can, for example, also use C# as it allows for unsafe code in specific areas. (Take a look at the scan0 pointer property of the bitmapdata class.) I've used C# successfully for image processing applications and they are definitely much faster than their java counterparts. I would not use any scripting language or java for such a purpose.

Answer 2

It's very east to manipulate the large multi-dimensional or complex arrays of pixel information that are pictures using high-level languages such as Python. There's a library called PIL (the Python Imaging Library) that is quite useful and will let you do general filters and transformations (change the brightness, soften, desaturate, crop, etc) as well as manipulate the raw pixel data.

It is the easiest and simplest image library I've used to date and can be extended to do whatever it is you're interested in (edge detection in very little code, for example).

Answer 3

Not only will C/C++ be faster, but most of the image processing sample code you find out there will be in C as well, so it will be easier to incorporate things you find.

Answer 4

if you are looking to numerical work on your images (think matrix) and you into Python check out http://www.scipy.org/PyLab - this is basically the ability to do matlab in python, buddy of mine swears by it.

Answer 5

(This might not apply for the OP who only wanted the bare basics -- but now that the speed issue was brought up, I do need to write this, just for the record.)

If you really need speed, it's better to forget about working on the pixel-by-pixel level, and rather see whether the operations that you need to perform could be vectorized. For example, for your C/C++ code you could use the excellent Intel IPP library (no, I don't work for Intel).

Answer 6

It depends a little on what you're trying to do.

If runtime speed is your issue then c++ is the best way to go.

If speed of development is an issue, though, I would suggest looking at java. You said that you wanted low level manipulation of pixels, which java will do for you. But the other thing that might be an issue is the handling of the various file formats. Java does have some very nice APIs to deal with the reading and writing of various image formats to file (in particular the java2d library. You choose to ignore the higher levels of the API)

If you do go for the c++ option (or python come to think of it) I would again suggest the use of a library to get you over the startup issues of reading and writing files. I've previously had success with libgd

Answer 7

What language do you know the best? To me, this is the real question. If you're going to spend months and months learning one particular language, then there's no real advantage in using Python or Java just for their (to be proven) development speed. I'm particularly proficient in C++ and I think that for this particular task I can be as speedy as a Java programmer, for example. With the aid of some good library (OpenCV comes to mind) you can create anything you need in a matter of a couple of lines of C++ code, really.

Answer 8

Short answer: C++ and OpenCV

Answer 9

I studied Artificial Intelligence and Computer Vision, thus I know pretty well the kind of tools that are used in this field.

Basically: you can use whatever you want as long as you know how it works behind the scene.

Now depending on what you want to achieve, you can either use:

• C language, but you will lose a lot of time in bugs checking and memory management when implementing your algorithms. So theoretically, this is the fastest language to do that kind of job, but if your algorithms are not computationnally efficient (in terms of complexity) or if you lose too much time in bugs checking, this is clearly not worth it. So I would advise to first implement your application in another language, and then later you can always optimize small parts of your code with C bindings.
• Octave/MatLab: very efficient language, almost as much as C, and you can make very elegant and succinct algorithms. If you are into vectorization, matrix and linear operations, you should go with that. However, you won't be able to develop a whole application with this language, it's more focused on algorithms, but then you can always develop an interface using another language later.
• Python: all-in-one elegant and accessible language, used in gigantically large scale applications such as Google and Facebook. You can do pretty much everything you want with Python, any kind of application. It will be perfectly adapted if you want to make a full application (with client interaction and all, not only algorithms), or if you want to quickly draft a prototype using existent libraries since Python has a very large set of high quality libraries, like OpenCV. However if you only want to make algorithms, you should better use Octave/MatLab.

The answer that was selected as a solution is very biaised, and you should be careful about this kind of archaic comment.

Nowadays, hardware is cheaper than wetware (humans), and thus, you should use languages where you will be able to produce results faster, even if it's at the cost of a few CPU cycles or memory space.

Also, a lot of people tends to think that as long as you implement your software in C/C++, you are making the Saint Graal of speedness: this is just not true. First, because algorithms complexity matters a lot more than the language you are using (a bad algorithm will never beat a better algorithm, even if implemented in the slowest language in the universe), and secondly because high-level languages are nowadays doing a lot of caching and speed optimization for you, and this can make your program run even faster than in C/C++.

Of course, you can always do everything of the above in C/C++, but how much of your time are you willing to waste to reinvent the wheel?

Answer 10

Short answer? I'd say C++, you have far more flexibility in manipulating raw chunks of memory than Python or Java.