LibCVC

An experimental pure-C binding to OpenCV 4. Intended to be used with libffi. Incomplete. Pre-alpha quality.

License: MIT.

Building

Install OpenCV v 4.0.1 or later
Checkout the repositiry
Build libcvc.so:

$ mkdir build && cd build
$ cmake ..
$ make

Rename it to libcvc.so.0.1 (yes, I know, but this is not important at this point).
Either copy libcvc.so.0.1 to /usr/local/lib64 or export LD_LIBRARY_PATH=$(pwd):$LD_LIBRARY_PATH.

An anticipatory FAQ

Why this binding is necessary?

Since the OpenCV 4.0 release, the official C API had been completely stripped off the project. As a result, developers working with all those scripting languages out there lost access to OpenCV.

OpenCV has got official Python and Java bindings, wasn't that enough?

There is also PyPy, and IronPython, and Ruby (with its variants), Tcl, Lua, Common Lisp and many others -- none of them has access to OpenCV via the official bindings.

Why pure C?

Because it is the only practical way of making libraries callable via libffi.

Why libffi?

Libffi is a de-facto standard and is available in virtually all scripting languages.

But most of the scripting lagnuages support C++ extensions (like RCpp). So, why C/libffi?

These C++ extensions are invariably implementation-specific, not language-specific. One cannot just take a CPython extension and use it with IronPython, for example. The same applies to Common Lisp and many other languages. libffi closes this gap by allowing developers to do exactly that: share extension libraries between implementations.

How complete is LibCVC?

It is very far from being complete. It might be considered somewhat usable at this point, depending on the task at hand.

However -- 100% completeness in terms of API coverage is not a goal. The reason is that OpenCV API contains numerous C++ specific artifacts that make no sense in other languages. Therefore, the goal is to achieve semantic completeness instead. For example, among all variadic OpenCV functions or methods solving the same problem, usually only the most specific one is wrapped.

Which languages/projects use LibCVC?

There is a Common Lisp wrapper - https://github.com/mikeivanov/see

Other Projects

There is yet another project that includes pure C bindings to OpenCV -- GoCV. Although a couple of technical ideas were borrowed from GoCV, it is a completely separate effort with different goals.

mikeivanov/libcvc