Cyphon OpenCV

cv2.cpp

#include <Python.h>
#include <opencv2/core/core.hpp>
#include <numpy/ndarrayobject.h>
#include <cstdio>

using namespace cv;

static PyObject* opencv_error = 0;

#define ERRWRAP2(expr)                       \
  try {                                      \
    PyAllowThreads allowThreads;             \
    expr;                                    \
  } catch (const cv::Exception& e) {         \
    PyErr_SetString(opencv_error, e.what()); \
    return 0;                                \
  }

static int failmsg(const char* fmt, ...) {
  char str[1000];

  va_list ap;
  va_start(ap, fmt);
  vsnprintf(str, sizeof(str), fmt, ap);
  va_end(ap);

  PyErr_SetString(PyExc_TypeError, str);
  return 0;
}

static PyObject* failmsgp(const char* fmt, ...) {
  char str[1000];

  va_list ap;
  va_start(ap, fmt);
  vsnprintf(str, sizeof(str), fmt, ap);
  va_end(ap);

  PyErr_SetString(PyExc_TypeError, str);
  return 0;
}

class PyAllowThreads {
 public:
  PyAllowThreads() : _state(PyEval_SaveThread()) {}
  ~PyAllowThreads() { PyEval_RestoreThread(_state); }

 private:
  PyThreadState* _state;
};

class PyEnsureGIL {
 public:
  PyEnsureGIL() : _state(PyGILState_Ensure()) {}
  ~PyEnsureGIL() { PyGILState_Release(_state); }

 private:
  PyGILState_STATE _state;
};

static size_t REFCOUNT_OFFSET =
    (size_t) &
    (((PyObject*)0)->ob_refcnt) +
        (0x12345678 != *(const size_t*)"\x78\x56\x34\x12\0\0\0\0\0") *
            sizeof(int);

static inline PyObject* pyObjectFromRefcount(const int* refcount) {
  return (PyObject*)((size_t)refcount - REFCOUNT_OFFSET);
}

static inline int* refcountFromPyObject(const PyObject* obj) {
  return (int*)((size_t)obj + REFCOUNT_OFFSET);
}

enum { ARG_NONE = 0, ARG_MAT = 1, ARG_SCALAR = 2 };

class NumpyAllocator : public MatAllocator {
 public:
  NumpyAllocator() { stdAllocator = Mat::getStdAllocator(); }
  ~NumpyAllocator() {}

  UMatData* allocate(PyObject* o, int dims, const int* sizes, int type,
                     size_t* step) const {
    UMatData* u = new UMatData(this);
    u->data = u->origdata = (uchar*)PyArray_DATA((PyArrayObject*)o);
    npy_intp* _strides = PyArray_STRIDES((PyArrayObject*)o);
    for (int i = 0; i < dims - 1; i++) step[i] = (size_t)_strides[i];
    step[dims - 1] = CV_ELEM_SIZE(type);
    u->size = sizes[0] * step[0];
    u->userdata = o;
    return u;
  }

  UMatData* allocate(int dims0, const int* sizes, int type, void* data,
                     size_t* step, int flags, UMatUsageFlags usageFlags) const {
    if (data != 0) {
      CV_Error(Error::StsAssert, "The data should normally be NULL!");
      // probably this is safe to do in such extreme case
      return stdAllocator->allocate(dims0, sizes, type, data, step, flags,
                                    usageFlags);
    }
    PyEnsureGIL gil;

    int depth = CV_MAT_DEPTH(type);
    int cn = CV_MAT_CN(type);
    const int f = (int)(sizeof(size_t) / 8);
    int typenum =
        depth == CV_8U
            ? NPY_UBYTE
            : depth == CV_8S
                  ? NPY_BYTE
                  : depth == CV_16U
                        ? NPY_USHORT
                        : depth == CV_16S
                              ? NPY_SHORT
                              : depth == CV_32S
                                    ? NPY_INT
                                    : depth == CV_32F
                                          ? NPY_FLOAT
                                          : depth == CV_64F
                                                ? NPY_DOUBLE
                                                : f * NPY_ULONGLONG +
                                                      (f ^ 1) * NPY_UINT;
    int i, dims = dims0;
    cv::AutoBuffer<npy_intp> _sizes(dims + 1);
    for (i = 0; i < dims; i++) _sizes[i] = sizes[i];
    if (cn > 1) _sizes[dims++] = cn;
    PyObject* o = PyArray_SimpleNew(dims, _sizes, typenum);
    if (!o)
      CV_Error_(Error::StsError,
                ("The numpy array of typenum=%d, ndims=%d can not be created",
                 typenum, dims));
    return allocate(o, dims0, sizes, type, step);
  }

  bool allocate(UMatData* u, int accessFlags, UMatUsageFlags usageFlags) const {
    return stdAllocator->allocate(u, accessFlags, usageFlags);
  }

  void deallocate(UMatData* u) const {
    if (u) {
      PyEnsureGIL gil;
      PyObject* o = (PyObject*)u->userdata;
      Py_XDECREF(o);
      delete u;
    }
  }

  const MatAllocator* stdAllocator;
};

NumpyAllocator g_numpyAllocator;

PyObject* fromMatToNDArray(const Mat& m) {
  if (!m.data) Py_RETURN_NONE;
  Mat temp, *p = (Mat*)&m;
  if (!p->u || p->allocator != &g_numpyAllocator) {
    temp.allocator = &g_numpyAllocator;
    ERRWRAP2(m.copyTo(temp));
    p = &temp;
  }
  PyObject* o = (PyObject*)p->u->userdata;
  Py_INCREF(o);
  return o;
}

Mat fromNDArrayToMat(PyObject* o) {
  cv::Mat m;
  bool allowND = true;
  if (!PyArray_Check(o)) {
    failmsg("argument is not a numpy array");
    if (!m.data) m.allocator = &g_numpyAllocator;
  } else {
    PyArrayObject* oarr = (PyArrayObject*)o;

    bool needcopy = false, needcast = false;
    int typenum = PyArray_TYPE(oarr), new_typenum = typenum;
    int type = typenum == NPY_UBYTE
                   ? CV_8U
                   : typenum == NPY_BYTE
                         ? CV_8S
                         : typenum == NPY_USHORT
                               ? CV_16U
                               : typenum == NPY_SHORT
                                     ? CV_16S
                                     : typenum == NPY_INT
                                           ? CV_32S
                                           : typenum == NPY_INT32
                                                 ? CV_32S
                                                 : typenum == NPY_FLOAT
                                                       ? CV_32F
                                                       : typenum == NPY_DOUBLE
                                                             ? CV_64F
                                                             : -1;

    if (type < 0) {
      if (typenum == NPY_INT64 || typenum == NPY_UINT64 || type == NPY_LONG) {
        needcopy = needcast = true;
        new_typenum = NPY_INT;
        type = CV_32S;
      } else {
        failmsg("Argument data type is not supported");
        m.allocator = &g_numpyAllocator;
        return m;
      }
    }

#ifndef CV_MAX_DIM
    const int CV_MAX_DIM = 32;
#endif

    int ndims = PyArray_NDIM(oarr);
    if (ndims >= CV_MAX_DIM) {
      failmsg("Dimensionality of argument is too high");
      if (!m.data) m.allocator = &g_numpyAllocator;
      return m;
    }

    int size[CV_MAX_DIM + 1];
    size_t step[CV_MAX_DIM + 1];
    size_t elemsize = CV_ELEM_SIZE1(type);
    const npy_intp* _sizes = PyArray_DIMS(oarr);
    const npy_intp* _strides = PyArray_STRIDES(oarr);
    bool ismultichannel = ndims == 3 && _sizes[2] <= CV_CN_MAX;

    for (int i = ndims - 1; i >= 0 && !needcopy; i--) {
      // these checks handle cases of
      //  a) multi-dimensional (ndims > 2) arrays, as well as simpler 1- and
      //  2-dimensional cases
      //  b) transposed arrays, where _strides[] elements go in non-descending
      //  order
      //  c) flipped arrays, where some of _strides[] elements are negative
      if ((i == ndims - 1 && (size_t)_strides[i] != elemsize) ||
          (i < ndims - 1 && _strides[i] < _strides[i + 1]))
        needcopy = true;
    }

    if (ismultichannel && _strides[1] != (npy_intp)elemsize * _sizes[2])
      needcopy = true;

    if (needcopy) {
      if (needcast) {
        o = PyArray_Cast(oarr, new_typenum);
        oarr = (PyArrayObject*)o;
      } else {
        oarr = PyArray_GETCONTIGUOUS(oarr);
        o = (PyObject*)oarr;
      }

      _strides = PyArray_STRIDES(oarr);
    }

    for (int i = 0; i < ndims; i++) {
      size[i] = (int)_sizes[i];
      step[i] = (size_t)_strides[i];
    }

    // handle degenerate case
    if (ndims == 0) {
      size[ndims] = 1;
      step[ndims] = elemsize;
      ndims++;
    }

    if (ismultichannel) {
      ndims--;
      type |= CV_MAKETYPE(0, size[2]);
    }

    if (ndims > 2 && !allowND) {
      failmsg("%s has more than 2 dimensions");
    } else {
      m = Mat(ndims, size, type, PyArray_DATA(oarr), step);
      m.u = g_numpyAllocator.allocate(o, ndims, size, type, step);
      m.addref();

      if (!needcopy) {
        Py_INCREF(o);
      }
    }
    m.allocator = &g_numpyAllocator;
  }
  return m;
}

module.h

#pragma once

#include "opencv2/core.hpp"
#include "opencv2/highgui.hpp"

using namespace cv;

void display_image(const Mat &img) {
  cv::imshow("", img);
  cv::waitKey(0);
}

module.pyx

import numpy as np
cimport numpy as np
from cpython.ref cimport PyObject

# Declares OpenCV's cv::Mat class
cdef extern from "opencv2/core/core.hpp":
    cdef cppclass Mat:
        pass

# Declares the official wrapper conversion functions + NumPy's import_array() function
cdef extern from "cv2.cpp":
  void import_array()
  PyObject* fromMatToNDArray(const Mat&)
  Mat fromNDArrayToMat(PyObject* o)

# Function to be called at initialization
cdef void *init():
  import_array()

# Python to C++ conversion
cdef Mat array2cvmat(object array):
  cdef PyObject* pyobject = <PyObject*> array
  cdef Mat mat = fromNDArrayToMat(pyobject)
  return <Mat> mat

cdef extern from "object_detection.h":
  void display_image(const Mat &)

def show_me(image):
  init()
  display_image(array2cvmat(image))

setup.py

#======== setup.py ===========
# Usage: python3 setup.py build_ext --inplace
from distutils.core import setup
from distutils.extension import Extension
from Cython.Distutils import build_ext
from Cython.Build import cythonize
import numpy
import subprocess

proc_libs = subprocess.check_output("pkg-config --libs opencv".split())
proc_incs = subprocess.check_output("pkg-config --cflags opencv".split())
libs = [lib for lib in str(proc_libs, "utf-8").split()]
incs = [numpy.get_include()]
incs.extend([inc for inc in str(proc_incs, "utf-8").split()])

setup(
  cmdclass = {'build_ext': build_ext},
  ext_modules = cythonize(Extension("module",
    sources = ["module.pyx"],
    language = "c++",
    include_dirs=incs,
    extra_link_args=libs
    )
  )
)