I was thinking of trying OpenCV for a project and noticed that it had C, C++ and Python.
I am trying to figure out whether I should use C++, C or Python -- and would like to use whatever has the best OpenCV support.
Just from looking at the index page for the various documentation it looks like the C++ bindings might have more features than the others? Is this true?
If C++ has more bindings, it seems that would be a more obvious choice for me, but I was just curious if it really has more features, etc than the others?
Thanks!
Actually Python binding was finished starting with release 2.2. So i would go with python if i were you, because the performance will be almost the same anyway as you are using c libraries in both cases. However python will get you there faster, safely and you will spend more time on your algorithm rather than getting things to build and run not mentioning memory management hassles
The Python interface is still being developed whereas the C++ interface (especially with the new Mat class) is quite mature. If you're comfortable in C++, I would highly recommend using it - else, you can start using Python and contribute back any features you think OpenCV needs :)
I think it depends how proficient you are in C++. The Mat interface does appear more modern than the old IPLImage C interface. The problem I'm having is that most of the examples you'll find on the web, or even here on stackoverflow are for the C interface (e.g. cvCvtColor), not for the C++ interface. So I'm really struggling to port the C examples to C++.
Even if you're very proficient in C or C++, you should use python to speed up your development (I should guess a 4x factor). Performance are really quite the same.
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What's this about?
We have a C++ application dealing with image processing and computer vision on videos using OpenCV, we're going to rewrite it from scratch and need some help deciding what technologies to use. More specifically, I need help on how to choose the technology I'd use.
About the app
The app's functionality is divided in modules that are called in an order defined by a configuration XML file and can also be changed in runtime, but not in realtime (i.e. the application doesn't need to close, but the processing will start from scratch). These modules share data in a central datapool.
Why are we starting from scratch?
This application wasn't planned to be as dynamic as it currently strives to be, so it's grown to be a collection of buggy patches, macros and workarounds; it's now full of memory leaks, unnecessary QT dependencies, slow conversions between QT and OpenCV image formats and compilation and testing times have grown too much.
Language choice
The original code used C++, just because the guy who originally started the project only knew C++. This may be a good choice, because we need it to be as fast as possible, but there may be better choices to account for the dynamic nature of the application.
We're limited by the languages supported by OpenCV (C++, Java and Python mainly; although I've read there is also support for Ruby, Ch, C# and any JVM language)
What is needed
Speed: We're aiming for realtime tracking. This may rule out Python and Ruby.
Class Instantiation by name: Although our C++ macros and class registration system work, a language designed to be dynamic that has it's own runtime would be nice. Maybe Objective-C++, or Java.
What would be ideal
Module/Plugin/Extension/Component Framework: Why reinvent the wheel, using a good framework for this would let us focus on what's special about our app. There are many options here. Objective-C has it's NSBundles; C++ has libraries like Boost.Extension, Pluma, DynObj, FxEngine, etc; C has C-Pluff; I'd even say there are too many options.
Runtime class loading and reloading: From a developing point of view, it would be interesting to be able to compile and reload just one module. I've seen this done in via code injection in Objective-C and using Java's reflection.
What am I missing?
I have too many interesting options!
Here's where I need help, based on your experiences in modular app development, with this constraints, what kind of language/framework feature should I be looking for?
What question should I make myself about this project that would let me narrow my search?
Edit
I hadn't noticed that OpenCV had GPU bindings only for C++, so I'm stuck with it.
Now that the language is fixed, the search has narrowed a lot. I could use Objective-C++ to get the dynamism needed (Obj-C runtime + NSBundle from Cocoa/GnuStep/Cocotron), which sounds complicated; or C++ with a framework.
So I'll now narrow my question to:
Is using NSBundle in a crossplatform way with Objective-C++ easier than it sounds?
What C++ framework will provide me with hot-swappable modules?
The main reason for swapping modules in runtime is to be able to change code in a fast way, would Runtime-Compiled C++ be a better solution?
Meta: I did my research on how to ask a question like this, I hope it's acceptable.
"What question should I make myself about this project that would let me narrow my search?"
if you need gpu support(cuda/ocl), your only choice is c++.
you can safely discard C, as it won't be supported in the near future
have no fear of python, even if you need direct pixel access, that's all numpy arrays (running c-code again)
i'd be a bit sceptical of ruby, c# ch and the like, since those bindings are community based, and might not be up to date / maintained properly, while the java & python bindings are machine - generated from the c++ api, and are part of the official distribution.
If you're looking for portability and have large memory for disposal then you can go with Java.
The performance hit between C++ and Java is not that bad. For conversion between Mat and other image format I'm still not sure, coz it needs deep copy to perform that, so if your code can display the image in openCV native format then you can fasten the application
pro :
You can stop worrying about memory leak
The project is much more portable compared to C/C++(this can be wrong if you can avoid using primitive datatypes which size is non consistent and for example always use int*_t in C)
cons:
slower than C/C++
more memory and CPU clock needed
http://www.ibm.com/developerworks/java/library/j-jtp09275/index.html
I'm looking to getting into image/video processing and was searching for a good library to start with. I've heard of two, OpenCV and IVT. I'd like to hear your opinion about which one is better to start with, what are the advantages/disadvantages of both and which one is better for possible commercial use later on.
Both offer very similar functionality - about 95% of it overlaps.
Both are BSD(ish) licensed and are widely used in commercial packages.
IVT is a cleaner more modern C++ design, but the new c++ bindings to opencv work well. Opencv has a few more 'C' type macros but it also means it's usable from C. Opencv is also very well supported by python and other languages, don't know about IVT.
There is also CImg. It requires only a single header file and uses C++ type templates so you write code like result = image.blur().sharpen().edge() almost like Mathematica!
It doesn't have the same depth of functionality, especially in things like recognition and machine learning, but is definitely easier to use. It's GPL/LGPL so usable commercially with care.
OpenCV is much more widely used, so has a bigger set of users who might answer questions - but it also has a MUCH bigger set of beginners asking questions !
The decider for me is that openCV is moving to support (almost) all the functionality in CUDA (ie on a parallel GPU) which is fantastic for anything needing realtime video processing.
Other than this I couldn't comment on the performance I didn't really benchmark IVT enough. OpenCV does use custom SSE2 assembler for a lot of the operations and uses TBB to parallel the rest if you have a multicore/hyperthreaded CPU.
I am a beginner like you and I personally say OpenCV. My first learning experience with OpenCV was more effortless than IVT because documentation was so neat and clear, also there are common beginner books, many tutorials and example projects for OpenCV.
I’m a native C++ programmer never knew anything about low level C, due to some circumstances I had to use C extensively. The outcome was me catching on a lot of C habits.
Know I’m trying to develop some Computer Vision project using OpenCV, TBB, OpenCL and OpenGL.
The thing is OpenCL is native C, so is TBB I guess not 100% sure about the TBB. As everybody knows C++ is an industrial Language and so Developing in it is a blast(at least for me) but after doing the main Which language should I use research? I’m know more concerned with C/C++ Code MIXING….
So my question is this Should I Develop the whole thing in C (Hard to maintain, expand and develop with) or should I stay with C++. And if I’m staying with C++ can someone plz direct me to a good way, strategy(Book, Tutorial) of mixing C/C++.
Thanks in advance.....
All the technologies you mention have C++ APIs. So if you are already comfortable using that, by all means do so. There does not need to be any mixing of C and C++ in one file, at all.
Only the OpenCL kernels are written in plain (OpenCL-) C. You do not mix the code, but you may have to pass data from your C++ code to your OpenCL kernel. Since you mention you now know both, that should not be a problem.
This C++ faq lite entry should be helpful. Mixing C and CPP
Greetings,
I am trying to decide between C and C++ for my robot. I am a 5+ year veteran of Visual Basic.NET, however I'm going with Linux (Ubuntu) on this robot, and there is a compatibility problem between Linux and the .NET Framework. I want to stick with whichever language I choose for all of my projects, so I want to make sure that I choose the most appropriate one for the task.
For reference, I will describe my current robot in progress and what I am going to do with it. I am in the process of building a full-sized R4 Astromech (yep, I'm one of those guys). I have incorporated a PC motherboard with an Intel Core 2 2.1 GHz processor, 1 GB RAM. I will be using a scratch-built parallel interface card to control the drive motors, head motor, as well as a secondary parallel interface card (going to a second parallel port) which all of the sensors (IR, Ultrasonic Ranging, Visual Recognition via webcam, etc.) will be going to. Commands will be given using speech recognition (currently have a VB.NET scratch-built recognition program that I will be adapting to the new language).
Given the specifications and desired goals listed above, would I be better off with C or C++? I greatly appreciate any suggestions that you might have.
Thanks!
Thaskalas
What do you mean by a compatibility problem? Have you looked at Mono? It's an open-source implementation of the .NET libraries. It's geared toward C# not VB.NET but if you're more comfortable in a .NET environment use that. Speed isn't really an issue here as a Core2Duo is plenty fast for what you need to do.
If Mono won't work for you, I'd recommend C++. There are a lot more libraries out there for C++ (or at least, I am familiar with more, e.g. Boost), which can use most C libraries too. There's no real speed penalty for using C++. While using C wouldn't be bad per-se, C++ has some benefits and no drawbacks, so it's probably the better choice.
I would recommend using ROS. It will let you get started with a sophisticated Inter-Process Communications manager, as well as a large library of sophisticated robotics code, including multiple implementations of SLAM and other critical robotics algorithms. ROS also lets you program in multiple languages, including C, C++, and Python, so you aren't stuck with one language or another down the road.
I would also recommend C++ and ROS. In our company we're migrating to it, because there's so many people working on it, expanding it, and adding lots of cool features.
With this, you can forget about implementing most of the basic low-level stuff and start working on what you intend to research.
It's really easy to set up and start developing.
Since you're running Linux on it, I'd recommend a split approach, where you do the lower-level (device interface, where you may need fast performance) stuff in C (or C++), and the higher level stuff in a modern language like C# (using Mono) or Java, or even Python.
Python especially is hugely expressive, has a large set of libraries, and has a pretty straightforward C interface.
Writing your high-level control stuff in a low-level language like C/C++ will get old fast (IMHO). Robots should be fun!
Have you considered D? It's a fairly new language, is compiled to native code and can link directly to C. (The entire C standard library is even available from D, and bindings to the POSIX API are included in the standard library.) Basically all you need to do to use any C library from D is compile it with a C compiler and translate the function prototypes, constant declarations, etc. in the header file.
D is low-level enough that an experimental kernel is written in it, but has modern features like garbage collection (though manual memory management is still permitted), builtin strings and arrays, and more advanced/easier to use template metaprogramming facilities than C++. The biggest disadvantage is lack of a mature toolchain and libraries for enterprise-y things, but for your purposes that probably doesn't matter. BTW, if you need to do a bunch of matrix manipulation and stuff, there's the SciD project, which provides nice templated wrappers over LAPACK and BLAS.
Use C++. You have the space. You can use it "as a better C" to start with.
C++ is a bigger tool bag; why would you not want that!? You need not use all the tools, but with C you'd have no choice. Most importantly with C++ you have the choice of using both C and C++ third-party libraries.
I know this question could be in vain, but it's just out of curiosity, and I'm still much a newb^^ Anyways I've been loving python for some time while learning it. My problem is obviously speed issues. I'd like to get into indie game creation, and for the short future, 2d and pygame will work.
But I'd eventually like to branch into the 3d area, and python is really too slow to make anything 3d and professional. So I'm wondering if there has ever been work to create a high-level language able to import and use c libraries? I've looked at Genie and it seems to be able to use certain libraries, but I'm not sure to what extent. Will I be able to use it for openGL programing, or in a c game engine?
I do know some lisp and enjoy it a lot, but there aren't a great many libraries out there for it. Which leads to the problem: I can't stand C syntax, but C has libraries galore that I could need! And game engines like irrlicht. Is there any language that can be used in place of C around C?
Thanks so much guys
Python can call functions in dynamically loaded C libraries (.so in unix, .dll in Windows) using the ctypes module.
There is also cython - a variation of python that compiles to C and can call C libraries directly. You can mix modules written in pure Python and cython.
You may also want to look at the numerous 3D game engines either written specifically for Python or with a python interface. The ones I have heard the most about (but not used) are Blender and Python-Ogre.
Panda3D is an engine which uses Python as it's "game logic" interface. You basically write everything in Python and the Panda3D backend (which I assume is mostly written in C or C++) is responsible for rendering.
Check out the gallery of projects that use Panda3D. It's not going to be AAA the-next-Gears-of-War level graphics, but it's still pretty impressive.
Using swig you can make C imports in various languages: lua, python, php, c# ...
See more info here about supported wrappers.
Python is able to use C libraries via the ctypes module. You'll have to write some Python code to import the C functions, but if the C API is clean and simple you'll have no trouble at all.
You might find these useful:
C functions from Python
Integrating Python, C and C++
I have been using PyOpenGL, it works great. Swig does its job if you want to call C/C++ libraries from Python.
I'm surprised that no-one has yet stated clearly that C++ is what you are looking for. Like you I have a distaste for C syntax, but that's a poor reason for avoiding C++ if you want to get into 3D gaming. Do you want to dive into 3D gaming, or do you want to sit on the edge of the pool crying that the water is too cold ?
I think you'll also find that C++ plays very well with OpenGL, which is probably not true of a lot of the alternatives that have already been suggested
To some extent, Cython might be what you are looking for. It allows you to use Python as a high level language, but then use C for the parts that need to be optimized.
But, at the end of the day, if you want to do 3D, just learning C or C++ may be the way to go. :-)
There are Python wrappers available for major open source game engines (Ogre, Irrlicht, etc.). Particularly Panda3D ought to have nice bindings.
If you'd like to have a look at .Net platform. You have the following solution:
Use C++/CLI to compile your C/C++ code into .Net assembly, the running time of this part would be as the same as your native C/C++ code.
Use any .Net language (C#, F#, IronPython) to develop high-level stuff using the low level library. For pure number crunching, C#/F# is usually 2-4 times slower than native C code, which is still far faster than Python. For non-number crunching tasks, C#/F# could sometimes match the speed of native code.