Added some functions for converting a numpy array into a pointer and its

dimensions.

dlib/python/numpy.h

+// Copyright (C) 2014  Davis E. King (davis@dlib.net)
+// License: Boost Software License   See LICENSE.txt for the full license.
+#ifndef DLIB_PYTHON_NuMPY_H__
+#define DLIB_PYTHON_NuMPY_H__
+
+#include <boost/python.hpp>
+#include <dlib/error.h>
+#include <dlib/algs.h>
+#include <dlib/string.h>
+
+// ----------------------------------------------------------------------------------------
+
+template <typename T>
+void validate_numpy_array_type (
+    boost::python::object& obj
+)
+{
+    using namespace boost::python;
+    const char ch = extract<char>(obj.attr("dtype").attr("char"));
+
+    if (dlib::is_same_type<T,double>::value && ch != 'd')
+        throw dlib::error("Expected numpy.ndarray of float64");
+    if (dlib::is_same_type<T,float>::value && ch != 'f')
+        throw dlib::error("Expected numpy.ndarray of float32");
+    if (dlib::is_same_type<T,dlib::int32>::value && ch != 'i')
+        throw dlib::error("Expected numpy.ndarray of int32");
+    if (dlib::is_same_type<T,unsigned char>::value && ch != 'B')
+        throw dlib::error("Expected numpy.ndarray of uint8");
+}
+
+// ----------------------------------------------------------------------------------------
+
+template <typename T, int dims>
+void get_numpy_ndarray_parts (
+    boost::python::object& obj,
+    T*& data,
+    long (&shape)[dims]
+)
+/*!
+    ensures
+        - extracts the pointer to the data from the given numpy ndarray.  Stores the shape
+          of the array into #shape.
+!*/
+{
+    Py_buffer pybuf;
+    if (PyObject_GetBuffer(obj.ptr(), &pybuf, PyBUF_ND | PyBUF_WRITABLE ))
+        throw dlib::error("Expected contiguous and writable numpy.ndarray.");
+
+    try
+    {
+        validate_numpy_array_type<T>(obj);
+        data = (T*)pybuf.buf;
+
+        if (pybuf.ndim > dims)
+            throw dlib::error("Expected array with " + dlib::cast_to_string(dims) + " dimensions.");
+
+        for (int i = 0; i < dims; ++i)
+        {
+            if (i < pybuf.ndim)
+                shape[i] = pybuf.shape[i];
+            else
+                shape[i] = 1;
+        }
+    }
+    catch(...)
+    {
+        PyBuffer_Release(&pybuf);
+        throw;
+    }
+    PyBuffer_Release(&pybuf);
+}
+
+// ----------------------------------------------------------------------------------------
+
+template <typename T, int dims>
+void get_numpy_ndarray_parts (
+    const boost::python::object& obj,
+    const T*& data,
+    long (&shape)[dims]
+)
+/*!
+    ensures
+        - extracts the pointer to the data from the given numpy ndarray.  Stores the shape
+          of the array into #shape.
+!*/
+{
+    Py_buffer pybuf;
+    if (PyObject_GetBuffer(obj.ptr(), &pybuf, PyBUF_ND ))
+        throw dlib::error("Expected contiguous numpy.ndarray.");
+
+    try
+    {
+        validate_numpy_array_type<T>(obj);
+        data = (const T*)pybuf.buf;
+
+        if (pybuf.ndim > dims)
+            throw dlib::error("Expected array with " + dlib::cast_to_string(dims) + " dimensions.");
+
+        for (int i = 0; i < dims; ++i)
+        {
+            if (i < pybuf.ndim)
+                shape[i] = pybuf.shape[i];
+            else
+                shape[i] = 1;
+        }
+    }
+    catch(...)
+    {
+        PyBuffer_Release(&pybuf);
+        throw;
+    }
+    PyBuffer_Release(&pybuf);
+}
+
+// ----------------------------------------------------------------------------------------
+
+#endif // DLIB_PYTHON_NuMPY_H__
+