I'm really sorry if my question might be too noob or something else. But, I find my self a little bit confusing between some commands found in OpenCV.
After browsing the OpenCV documentation , I found that there are commands like cvMemStorage and cv::MemStorage, cvMat and cv::Mat, cvSeq and cv::Seq, cvNormalBayesClassifier and cv::NormalBayesClassifier.
So, what are the differences between those commands?
Are they just a different style of commands between the C and C++ style?
So why don't they (OpenCV team) just use one style in most of the c and c++ world?
Any help and comments would be really appreciated.
Thank you
The convention seems to be that cvSomething is a C type or function, and cv::Something is the corresponding C++ version. In C++, cv is a namespace.
OpenCV maintains both C and a C++ interfaces, which is the reason you get both variants (there are also python bindings, which can make the all-in-one documentation confusing).
The core library of OpenCV version 2.x is written in C++. The coding convention is to have everything in the namespace cv. (See here or here).
The old API (version 1.x) was a C API. The convention was to add the prefix cv.
The old 1.x API is still exposed to client code. Usually, you will not need it. (As stated in the OpenCV documentation for Dynamic structure (since you referenced the cvCreateMemStorage), "if you use the new C++, Python, Java etc interface, you will unlikely need this functionality. Use std::vector or other high-level data structures.")
Related
I'm building a cross-platform mobile application and I was suggested to use OF environment and compile my application using Xcode. I'm a Mac user and I started programming few time ago (so I'm really a beginner).
I need some class to get information about position and rotation so I was thinking to have a look at some SDK such as MoSync or CMDeviceMotion in order to understand which one is the most suitable to my purpose.
I also noted here:
https://developer.apple.com/library/ios/documentation/CoreMotion/Reference/CMDeviceMotion_Class/index.html#//apple_ref/doc/c_ref/CMDeviceMotion
that CMDeviceMotion is written for Obj-C and Swift.
So I have two question:
is it possible add to the main project libraries that are not part of OF?
should I use only C/C++ class?
Thanks.
I'm not sure if stackoverflow is the right place to ask a q like this, since any answer is very much prone to subjectivity.
I don't think there's a lot of valid reasons to even try to connect "MoSync" with OF, since they are both in a way "platforms" for developing apps, supporting different languages (javascript on the first and c++ on the latter). It is possible to mix objective-c (and swift) code with c++, so you can combine CMDeviceMotion with OF.
However to answer your question: It seems that if you want to have device information you don't need to go out of the scope of openFrameworks. Take a look at the "ofxIOSCoreLocation"class of OpenFrameworks/ofxIOS. It provides means for altitude, location, direction and so forth.
It is very possible to cross Objective-C and C++ with what is called Objective-C++ (by standard .mm instead of cpp), in openFrameworks.
Limitations and features: https://en.wikipedia.org/wiki/Objective-C#Objective-C.2B.2B
You can then from the Objective-C++ class (lets say for example ofApp.h), call Objective C delegates and functions directly.
You can not embed swift like this, however you there are some methods of using objective-c middle man class.
I have probably trivial problem. I'm trying to use GEOS library. I have my functions using GEOS library in my own library. And I want to use this library in my QGIS plugin writen in C++. The problem is, that functions in my library work with geos::geom::Geometry, but in QGIS plugin, there is GEOSGeometry. I thought that it is the same thing, but it probably isn't.
Can anyone explain me the difference between these two and give me an advice, how to convert them to each other or tell me what I'm doing wrong? Thanks.
GEOSGeometry is a typedef for the structure used in the C (not C++) API. It is stated on the official documentation that the use of the C API is preferred to the C++ API as it may be more stable (in terms of future changes).
I'm not sure if you can simply cast the structures (I'd advise against it). I suggest you use the C API instead of the C++ API.
No, you can not simply cast between GEOS C API type GEOSGeometry and C++ API types from hierarchy rooted at geos::geom::Geometry class.
You can, however, convert your geometries using WKB as an interchange format, between the C API and the C++ API objects.
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
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.
(mingw32, windows xp)
Hello, I am attempting to migrate from Java to c++. I am confused and frustrated about finding, installing, and compiling non-standard c++ libraries. in Java it's so convenient they stuffed every functionality and documentation ever needed in java's standard api. Is there a list of essential c++ library such as Threading, gui, networking, image\ audio processing, xml, etc.etc. in one place? or possibly, offered as a single package?
I tried installing QT library for weeks and it wont even compile. in Java i used to learn by trial-and-error to learn new aspect of functionality, but that would be impossible if i can't fetch and run new api in the first place.
please, i need your suggestion, originally i wanted to break free of Java's abstraction, but now i just want to be able to use c++ before I decided shooting myself in the head.
The C++ standard library is extremely light. It contains nowhere near the functionality offered by the Java runtimes or by the .NET CLR.
The Boost libraries add a whole bunch of functionality to C++, but not much (if any) in the area of user interface.
For UI, there's the question of which platform you're targetting. If it's Win32, then you can use the straight Win32 API (mostly designed for C, but there are some C++ wrappers for parts of it). If you want cross-platform, then you're looking at QT or GTK (although there are others).
But, as Andrew already said: "why do you want to learn C++ anyway?". Don't get me wrong: I program in C++ for a living, and actually enjoy it (although I'm beginning to suspect a case of Stockholm Syndrome). If I had to start again, I'd go with a more modern language and environment (Java or C#; or Ruby or Python).
My advice would be: take it one step at a time.
First, figure out how to include a pre-built library in your code. I'd recommend starting with ZLib (it's got a very easy design to work with and it's also a useful tool to have available). Once you've got the pre-built library working, remove it and try compiling ZLib from the source code. Ask on Stack Overflow if you need help at any point, we'll get you through it.
By the time you get that working, you should have all the knowledge you need to get Qt compiled and installed too.
Threading, XML, Networking, some image generation, encoding and processing - boost provides those. As for XML, there's for example Arabica - it abstracts away platform-specific libraries by wrapping them with a nice standard C++ scent.
The GUI part is a different problem.
There's Qt, wxWidgets, gtk with c++ bindings (gtkmm), native libraries for each platform and their C++ wrappers (WTL is an excellent library for Win32), but as the C++ standard evolved and boost is becoming part of the standard (C++0x coming soon), there are no GUI frameworks that leverage those standard facilities and introduce their own instead. They do their job very well though.