feat: common fixed size sequence conversion for Python bindings

modules/core/include/opencv2/core/bindings_utils.hpp

@@ -78,6 +78,41 @@ String testOverloadResolution(const Rect& rect)
                   rect.width, rect.height);
 }
 
+CV_WRAP static inline
+String dumpRect(const Rect& argument)
+{
+    return format("rect: (x=%d, y=%d, w=%d, h=%d)", argument.x, argument.y,
+                  argument.width, argument.height);
+}
+
+CV_WRAP static inline
+String dumpTermCriteria(const TermCriteria& argument)
+{
+    return format("term_criteria: (type=%d, max_count=%d, epsilon=%lf",
+                  argument.type, argument.maxCount, argument.epsilon);
+}
+
+CV_WRAP static inline
+String dumpRotatedRect(const RotatedRect& argument)
+{
+    return format("rotated_rect: (c_x=%f, c_y=%f, w=%f, h=%f, a=%f)",
+                  argument.center.x, argument.center.y, argument.size.width,
+                  argument.size.height, argument.angle);
+}
+
+CV_WRAP static inline
+String dumpRange(const Range& argument)
+{
+    if (argument == Range::all())
+    {
+        return "range: all";
+    }
+    else
+    {
+        return format("range: (s=%d, e=%d)", argument.start, argument.end);
+    }
+}
+
 CV_WRAP static inline
 AsyncArray testAsyncArray(InputArray argument)
 {

modules/python/src2/cv2.cpp

@@ -404,6 +404,63 @@ void pyPopulateArgumentConversionErrors()
     }
 }
 
+struct SafeSeqItem
+{
+    PyObject * item;
+    SafeSeqItem(PyObject *obj, size_t idx) { item = PySequence_GetItem(obj, idx); }
+    ~SafeSeqItem() { Py_XDECREF(item); }
+
+private:
+    SafeSeqItem(const SafeSeqItem&); // = delete
+    SafeSeqItem& operator=(const SafeSeqItem&); // = delete
+};
+
+template <class T>
+class RefWrapper
+{
+public:
+    RefWrapper(T& item) : item_(item) {}
+
+    T& get() CV_NOEXCEPT { return item_; }
+
+private:
+    T& item_;
+};
+
+// In order to support this conversion on 3.x branch - use custom reference_wrapper
+// and C-style array instead of std::array<T, N>
+template <class T, std::size_t N>
+bool parseSequence(PyObject* obj, RefWrapper<T> (&value)[N], const ArgInfo& info)
+{
+    if (!obj || obj == Py_None)
+    {
+        return true;
+    }
+    if (!PySequence_Check(obj))
+    {
+        failmsg("Can't parse '%s'. Input argument doesn't provide sequence "
+                "protocol", info.name);
+        return false;
+    }
+    const std::size_t sequenceSize = PySequence_Size(obj);
+    if (sequenceSize != N)
+    {
+        failmsg("Can't parse '%s'. Expected sequence length %lu, got %lu",
+                info.name, N, sequenceSize);
+        return false;
+    }
+    for (std::size_t i = 0; i < N; ++i)
+    {
+        SafeSeqItem seqItem(obj, i);
+        if (!pyopencv_to(seqItem.item, value[i].get(), info))
+        {
+            failmsg("Can't parse '%s'. Sequence item with index %lu has a "
+                    "wrong type", info.name, i);
+            return false;
+        }
+    }
+    return true;
+}
 } // namespace
 
 typedef std::vector<uchar> vector_uchar;
@@ -777,13 +834,6 @@ static PyObject* pyopencv_from(void*& ptr)
     return PyLong_FromVoidPtr(ptr);
 }
 
-struct SafeSeqItem
-{
-    PyObject * item;
-    SafeSeqItem(PyObject *obj, size_t idx) { item = PySequence_GetItem(obj, idx); }
-    ~SafeSeqItem() { Py_XDECREF(item); }
-};
-
 static bool pyopencv_to(PyObject *o, Scalar& s, const ArgInfo& info)
 {
     if(!o || o == Py_None)
@@ -1108,10 +1158,9 @@ bool pyopencv_to(PyObject* obj, String &value, const ArgInfo& info)
 template<>
 bool pyopencv_to(PyObject* obj, Size& sz, const ArgInfo& info)
 {
-    CV_UNUSED(info);
-    if(!obj || obj == Py_None)
-        return true;
-    return PyArg_ParseTuple(obj, "ii", &sz.width, &sz.height) > 0;
+    RefWrapper<int> values[] = {RefWrapper<int>(sz.width),
+                                RefWrapper<int>(sz.height)};
+    return parseSequence(obj, values, info);
 }
 
 template<>
@@ -1123,10 +1172,9 @@ PyObject* pyopencv_from(const Size& sz)
 template<>
 bool pyopencv_to(PyObject* obj, Size_<float>& sz, const ArgInfo& info)
 {
-    CV_UNUSED(info);
-    if(!obj || obj == Py_None)
-        return true;
-    return PyArg_ParseTuple(obj, "ff", &sz.width, &sz.height) > 0;
+    RefWrapper<float> values[] = {RefWrapper<float>(sz.width),
+                                  RefWrapper<float>(sz.height)};
+    return parseSequence(obj, values, info);
 }
 
 template<>
@@ -1138,10 +1186,10 @@ PyObject* pyopencv_from(const Size_<float>& sz)
 template<>
 bool pyopencv_to(PyObject* obj, Rect& r, const ArgInfo& info)
 {
-    CV_UNUSED(info);
-    if(!obj || obj == Py_None)
-        return true;
-    return PyArg_ParseTuple(obj, "iiii", &r.x, &r.y, &r.width, &r.height) > 0;
+    RefWrapper<int> values[] = {RefWrapper<int>(r.x), RefWrapper<int>(r.y),
+                                RefWrapper<int>(r.width),
+                                RefWrapper<int>(r.height)};
+    return parseSequence(obj, values, info);
 }
 
 template<>
@@ -1153,10 +1201,10 @@ PyObject* pyopencv_from(const Rect& r)
 template<>
 bool pyopencv_to(PyObject* obj, Rect2d& r, const ArgInfo& info)
 {
-    CV_UNUSED(info);
-    if(!obj || obj == Py_None)
-        return true;
-    return PyArg_ParseTuple(obj, "dddd", &r.x, &r.y, &r.width, &r.height) > 0;
+    RefWrapper<double> values[] = {
+        RefWrapper<double>(r.x), RefWrapper<double>(r.y),
+        RefWrapper<double>(r.width), RefWrapper<double>(r.height)};
+    return parseSequence(obj, values, info);
 }
 
 template<>
@@ -1168,44 +1216,17 @@ PyObject* pyopencv_from(const Rect2d& r)
 template<>
 bool pyopencv_to(PyObject* obj, Range& r, const ArgInfo& info)
 {
-    CV_UNUSED(info);
-    if(!obj || obj == Py_None)
-        return true;
-    while (PySequence_Check(obj))
+    if (!obj || obj == Py_None)
     {
-        if (2 != PySequence_Size(obj))
-        {
-            failmsg("Range value for argument '%s' is longer than 2", info.name);
-            return false;
-        }
-        {
-            SafeSeqItem item_wrap(obj, 0);
-            PyObject *item = item_wrap.item;
-            if (PyInt_Check(item)) {
-                r.start = (int)PyInt_AsLong(item);
-            } else {
-                failmsg("Range.start value for argument '%s' is not integer", info.name);
-                break;
-            }
-        }
-        {
-            SafeSeqItem item_wrap(obj, 1);
-            PyObject *item = item_wrap.item;
-            if (PyInt_Check(item)) {
-                r.end = (int)PyInt_AsLong(item);
-            } else {
-                failmsg("Range.end value for argument '%s' is not integer", info.name);
-                break;
-            }
-        }
         return true;
     }
-    if(PyObject_Size(obj) == 0)
+    if (PyObject_Size(obj) == 0)
     {
         r = Range::all();
         return true;
     }
-    return PyArg_ParseTuple(obj, "ii", &r.start, &r.end) > 0;
+    RefWrapper<int> values[] = {RefWrapper<int>(r.start), RefWrapper<int>(r.end)};
+    return parseSequence(obj, values, info);
 }
 
 template<>
@@ -1217,64 +1238,42 @@ PyObject* pyopencv_from(const Range& r)
 template<>
 bool pyopencv_to(PyObject* obj, Point& p, const ArgInfo& info)
 {
-    CV_UNUSED(info);
-    if(!obj || obj == Py_None)
-        return true;
-    if(PyComplex_Check(obj))
-    {
-        p.x = saturate_cast<int>(PyComplex_RealAsDouble(obj));
-        p.y = saturate_cast<int>(PyComplex_ImagAsDouble(obj));
-        return true;
-    }
-    return PyArg_ParseTuple(obj, "ii", &p.x, &p.y) > 0;
+    RefWrapper<int> values[] = {RefWrapper<int>(p.x), RefWrapper<int>(p.y)};
+    return parseSequence(obj, values, info);
 }
 
-template<>
+template <>
 bool pyopencv_to(PyObject* obj, Point2f& p, const ArgInfo& info)
 {
-    CV_UNUSED(info);
-    if(!obj || obj == Py_None)
-        return true;
-    if (PyComplex_Check(obj))
-    {
-        p.x = saturate_cast<float>(PyComplex_RealAsDouble(obj));
-        p.y = saturate_cast<float>(PyComplex_ImagAsDouble(obj));
-        return true;
-    }
-    return PyArg_ParseTuple(obj, "ff", &p.x, &p.y) > 0;
+    RefWrapper<float> values[] = {RefWrapper<float>(p.x),
+                                  RefWrapper<float>(p.y)};
+    return parseSequence(obj, values, info);
 }
 
 template<>
 bool pyopencv_to(PyObject* obj, Point2d& p, const ArgInfo& info)
 {
-    CV_UNUSED(info);
-    if(!obj || obj == Py_None)
-        return true;
-    if(PyComplex_Check(obj))
-    {
-        p.x = PyComplex_RealAsDouble(obj);
-        p.y = PyComplex_ImagAsDouble(obj);
-        return true;
-    }
-    return PyArg_ParseTuple(obj, "dd", &p.x, &p.y) > 0;
+    RefWrapper<double> values[] = {RefWrapper<double>(p.x),
+                                   RefWrapper<double>(p.y)};
+    return parseSequence(obj, values, info);
 }
 
 template<>
 bool pyopencv_to(PyObject* obj, Point3f& p, const ArgInfo& info)
 {
-    CV_UNUSED(info);
-    if(!obj || obj == Py_None)
-        return true;
-    return PyArg_ParseTuple(obj, "fff", &p.x, &p.y, &p.z) > 0;
+    RefWrapper<float> values[] = {RefWrapper<float>(p.x),
+                                  RefWrapper<float>(p.y),
+                                  RefWrapper<float>(p.z)};
+    return parseSequence(obj, values, info);
 }
 
 template<>
 bool pyopencv_to(PyObject* obj, Point3d& p, const ArgInfo& info)
 {
-    CV_UNUSED(info);
-    if(!obj || obj == Py_None)
-        return true;
-    return PyArg_ParseTuple(obj, "ddd", &p.x, &p.y, &p.z) > 0;
+    RefWrapper<double> values[] = {RefWrapper<double>(p.x),
+                                   RefWrapper<double>(p.y),
+                                   RefWrapper<double>(p.z)};
+    return parseSequence(obj, values, info);
 }
 
 template<>
@@ -1297,74 +1296,66 @@ PyObject* pyopencv_from(const Point3f& p)
 
 static bool pyopencv_to(PyObject* obj, Vec4d& v, ArgInfo& info)
 {
-    CV_UNUSED(info);
-    if (!obj)
-        return true;
-    return PyArg_ParseTuple(obj, "dddd", &v[0], &v[1], &v[2], &v[3]) > 0;
+    RefWrapper<double> values[] = {RefWrapper<double>(v[0]), RefWrapper<double>(v[1]),
+                                   RefWrapper<double>(v[2]), RefWrapper<double>(v[3])};
+    return parseSequence(obj, values, info);
 }
 
 static bool pyopencv_to(PyObject* obj, Vec4f& v, ArgInfo& info)
 {
-    CV_UNUSED(info);
-    if (!obj)
-        return true;
-    return PyArg_ParseTuple(obj, "ffff", &v[0], &v[1], &v[2], &v[3]) > 0;
+    RefWrapper<float> values[] = {RefWrapper<float>(v[0]), RefWrapper<float>(v[1]),
+                                  RefWrapper<float>(v[2]), RefWrapper<float>(v[3])};
+    return parseSequence(obj, values, info);
 }
 
 static bool pyopencv_to(PyObject* obj, Vec4i& v, ArgInfo& info)
 {
-    CV_UNUSED(info);
-    if (!obj)
-        return true;
-    return PyArg_ParseTuple(obj, "iiii", &v[0], &v[1], &v[2], &v[3]) > 0;
+    RefWrapper<int> values[] = {RefWrapper<int>(v[0]), RefWrapper<int>(v[1]),
+                                RefWrapper<int>(v[2]), RefWrapper<int>(v[3])};
+    return parseSequence(obj, values, info);
 }
 
 static bool pyopencv_to(PyObject* obj, Vec3d& v, ArgInfo& info)
 {
-    CV_UNUSED(info);
-    if (!obj)
-        return true;
-    return PyArg_ParseTuple(obj, "ddd", &v[0], &v[1], &v[2]) > 0;
+    RefWrapper<double> values[] = {RefWrapper<double>(v[0]),
+                                   RefWrapper<double>(v[1]),
+                                   RefWrapper<double>(v[2])};
+    return parseSequence(obj, values, info);
 }
 
 static bool pyopencv_to(PyObject* obj, Vec3f& v, ArgInfo& info)
 {
-    CV_UNUSED(info);
-    if (!obj)
-        return true;
-    return PyArg_ParseTuple(obj, "fff", &v[0], &v[1], &v[2]) > 0;
+    RefWrapper<float> values[] = {RefWrapper<float>(v[0]),
+                                  RefWrapper<float>(v[1]),
+                                  RefWrapper<float>(v[2])};
+    return parseSequence(obj, values, info);
 }
 
 static bool pyopencv_to(PyObject* obj, Vec3i& v, ArgInfo& info)
 {
-    CV_UNUSED(info);
-    if (!obj)
-        return true;
-    return PyArg_ParseTuple(obj, "iii", &v[0], &v[1], &v[2]) > 0;
+    RefWrapper<int> values[] = {RefWrapper<int>(v[0]), RefWrapper<int>(v[1]),
+                                RefWrapper<int>(v[2])};
+    return parseSequence(obj, values, info);
 }
 
 static bool pyopencv_to(PyObject* obj, Vec2d& v, ArgInfo& info)
 {
-    CV_UNUSED(info);
-    if (!obj)
-        return true;
-    return PyArg_ParseTuple(obj, "dd", &v[0], &v[1]) > 0;
+    RefWrapper<double> values[] = {RefWrapper<double>(v[0]),
+                                   RefWrapper<double>(v[1])};
+    return parseSequence(obj, values, info);
 }
 
 static bool pyopencv_to(PyObject* obj, Vec2f& v, ArgInfo& info)
 {
-    CV_UNUSED(info);
-    if (!obj)
-        return true;
-    return PyArg_ParseTuple(obj, "ff", &v[0], &v[1]) > 0;
+    RefWrapper<float> values[] = {RefWrapper<float>(v[0]),
+                                  RefWrapper<float>(v[1])};
+    return parseSequence(obj, values, info);
 }
 
 static bool pyopencv_to(PyObject* obj, Vec2i& v, ArgInfo& info)
 {
-    CV_UNUSED(info);
-    if (!obj)
-        return true;
-    return PyArg_ParseTuple(obj, "ii", &v[0], &v[1]) > 0;
+    RefWrapper<int> values[] = {RefWrapper<int>(v[0]), RefWrapper<int>(v[1])};
+    return parseSequence(obj, values, info);
 }
 
 template<>
@@ -1705,12 +1696,54 @@ template<> struct pyopencvVecConverter<RotatedRect>
 };
 
 template<>
-bool pyopencv_to(PyObject *obj, TermCriteria& dst, const ArgInfo& info)
+bool pyopencv_to(PyObject* obj, TermCriteria& dst, const ArgInfo& info)
 {
-    CV_UNUSED(info);
-    if(!obj)
+    if (!obj || obj == Py_None)
+    {
         return true;
-    return PyArg_ParseTuple(obj, "iid", &dst.type, &dst.maxCount, &dst.epsilon) > 0;
+    }
+    if (!PySequence_Check(obj))
+    {
+        failmsg("Can't parse '%s' as TermCriteria."
+                "Input argument doesn't provide sequence protocol",
+                info.name);
+        return false;
+    }
+    const std::size_t sequenceSize = PySequence_Size(obj);
+    if (sequenceSize != 3) {
+        failmsg("Can't parse '%s' as TermCriteria. Expected sequence length 3, "
+                "got %lu",
+                info.name, sequenceSize);
+        return false;
+    }
+    {
+        const String typeItemName = format("'%s' criteria type", info.name);
+        const ArgInfo typeItemInfo(typeItemName.c_str(), false);
+        SafeSeqItem typeItem(obj, 0);
+        if (!pyopencv_to(typeItem.item, dst.type, typeItemInfo))
+        {
+            return false;
+        }
+    }
+    {
+        const String maxCountItemName = format("'%s' max count", info.name);
+        const ArgInfo maxCountItemInfo(maxCountItemName.c_str(), false);
+        SafeSeqItem maxCountItem(obj, 1);
+        if (!pyopencv_to(maxCountItem.item, dst.maxCount, maxCountItemInfo))
+        {
+            return false;
+        }
+    }
+    {
+        const String epsilonItemName = format("'%s' epsilon", info.name);
+        const ArgInfo epsilonItemInfo(epsilonItemName.c_str(), false);
+        SafeSeqItem epsilonItem(obj, 2);
+        if (!pyopencv_to(epsilonItem.item, dst.epsilon, epsilonItemInfo))
+        {
+            return false;
+        }
+    }
+    return true;
 }
 
 template<>
@@ -1720,12 +1753,54 @@ PyObject* pyopencv_from(const TermCriteria& src)
 }
 
 template<>
-bool pyopencv_to(PyObject *obj, RotatedRect& dst, const ArgInfo& info)
+bool pyopencv_to(PyObject* obj, RotatedRect& dst, const ArgInfo& info)
 {
-    CV_UNUSED(info);
-    if(!obj)
+    if (!obj || obj == Py_None)
+    {
         return true;
-    return PyArg_ParseTuple(obj, "(ff)(ff)f", &dst.center.x, &dst.center.y, &dst.size.width, &dst.size.height, &dst.angle) > 0;
+    }
+    if (!PySequence_Check(obj))
+    {
+        failmsg("Can't parse '%s' as RotatedRect."
+                "Input argument doesn't provide sequence protocol",
+                info.name);
+        return false;
+    }
+    const std::size_t sequenceSize = PySequence_Size(obj);
+    if (sequenceSize != 3)
+    {
+        failmsg("Can't parse '%s' as RotatedRect. Expected sequence length 3, got %lu",
+                info.name, sequenceSize);
+        return false;
+    }
+    {
+        const String centerItemName = format("'%s' center point", info.name);
+        const ArgInfo centerItemInfo(centerItemName.c_str(), false);
+        SafeSeqItem centerItem(obj, 0);
+        if (!pyopencv_to(centerItem.item, dst.center, centerItemInfo))
+        {
+            return false;
+        }
+    }
+    {
+        const String sizeItemName = format("'%s' size", info.name);
+        const ArgInfo sizeItemInfo(sizeItemName.c_str(), false);
+        SafeSeqItem sizeItem(obj, 1);
+        if (!pyopencv_to(sizeItem.item, dst.size, sizeItemInfo))
+        {
+            return false;
+        }
+    }
+    {
+        const String angleItemName = format("'%s' angle", info.name);
+        const ArgInfo angleItemInfo(angleItemName.c_str(), false);
+        SafeSeqItem angleItem(obj, 2);
+        if (!pyopencv_to(angleItem.item, dst.angle, angleItemInfo))
+        {
+            return false;
+        }
+    }
+    return true;
 }
 
 template<>

modules/python/test/test_misc.py

@@ -3,6 +3,7 @@ from __future__ import print_function
 
 import ctypes
 from functools import partial
+from collections import namedtuple
 
 import numpy as np
 import cv2 as cv
@@ -378,6 +379,84 @@ class Arguments(NewOpenCVTests):
             with self.assertRaises((TypeError), msg=get_no_exception_msg(not_convertible)):
                 _ = cv.utils.dumpString(not_convertible)
 
+    def test_parse_to_rect_convertible(self):
+        Rect = namedtuple('Rect', ('x', 'y', 'w', 'h'))
+        try_to_convert = partial(self._try_to_convert, cv.utils.dumpRect)
+        for convertible in ((1, 2, 4, 5), [5, 3, 10, 20], np.array([10, 20, 23, 10]),
+                            Rect(10, 30, 40, 55), tuple(np.array([40, 20, 24, 20])),
+                            list(np.array([20, 40, 30, 35]))):
+            expected = 'rect: (x={}, y={}, w={}, h={})'.format(*convertible)
+            actual = try_to_convert(convertible)
+            self.assertEqual(expected, actual,
+                             msg=get_conversion_error_msg(convertible, expected, actual))
+
+    def test_parse_to_rect_not_convertible(self):
+        for not_convertible in (np.empty(shape=(4, 1)), (), [], np.array([]), (12, ),
+                                [3, 4, 5, 10, 123], {1: 2, 3:4, 5:10, 6:30},
+                                '1234', np.array([1, 2, 3, 4], dtype=np.float32),
+                                np.array([[1, 2], [3, 4], [5, 6], [6, 8]]), (1, 2, 5, 1.5)):
+            with self.assertRaises((TypeError), msg=get_no_exception_msg(not_convertible)):
+                _ = cv.utils.dumpRect(not_convertible)
+
+    def test_parse_to_rotated_rect_convertible(self):
+        RotatedRect = namedtuple('RotatedRect', ('center', 'size', 'angle'))
+        try_to_convert = partial(self._try_to_convert, cv.utils.dumpRotatedRect)
+        for convertible in (((2.5, 2.5), (10., 20.), 12.5), [[1.5, 10.5], (12.5, 51.5), 10],
+                            RotatedRect((10, 40), np.array([10.5, 20.5]), 5),
+                            np.array([[10, 6], [50, 50], 5.5], dtype=object)):
+            center, size, angle = convertible
+            expected = 'rotated_rect: (c_x={:.6f}, c_y={:.6f}, w={:.6f},' \
+                       ' h={:.6f}, a={:.6f})'.format(center[0], center[1],
+                                                     size[0], size[1], angle)
+            actual = try_to_convert(convertible)
+            self.assertEqual(expected, actual,
+                             msg=get_conversion_error_msg(convertible, expected, actual))
+
+    def test_parse_to_rotated_rect_not_convertible(self):
+        for not_convertible in ([], (), np.array([]), (123, (45, 34), 1), {1: 2, 3: 4}, 123,
+                                np.array([[123, 123, 14], [1, 3], 56], dtype=object), '123'):
+            with self.assertRaises((TypeError), msg=get_no_exception_msg(not_convertible)):
+                _ = cv.utils.dumpRotatedRect(not_convertible)
+
+    def test_parse_to_term_criteria_convertible(self):
+        TermCriteria = namedtuple('TermCriteria', ('type', 'max_count', 'epsilon'))
+        try_to_convert = partial(self._try_to_convert, cv.utils.dumpTermCriteria)
+        for convertible in ((1, 10, 1e-3), [2, 30, 1e-1], np.array([10, 20, 0.5], dtype=object),
+                            TermCriteria(0, 5, 0.1)):
+            expected = 'term_criteria: (type={}, max_count={}, epsilon={:.6f}'.format(*convertible)
+            actual = try_to_convert(convertible)
+            self.assertEqual(expected, actual,
+                             msg=get_conversion_error_msg(convertible, expected, actual))
+
+    def test_parse_to_term_criteria_not_convertible(self):
+        for not_convertible in ([], (), np.array([]), [1, 4], (10,), (1.5, 34, 0.1),
+                                {1: 5, 3: 5, 10: 10}, '145'):
+            with self.assertRaises((TypeError), msg=get_no_exception_msg(not_convertible)):
+                _ = cv.utils.dumpTermCriteria(not_convertible)
+
+    def test_parse_to_range_convertible_to_all(self):
+        try_to_convert = partial(self._try_to_convert, cv.utils.dumpRange)
+        for convertible in ((), [], np.array([])):
+            expected = 'range: all'
+            actual = try_to_convert(convertible)
+            self.assertEqual(expected, actual,
+                             msg=get_conversion_error_msg(convertible, expected, actual))
+
+    def test_parse_to_range_convertible(self):
+        Range = namedtuple('Range', ('start', 'end'))
+        try_to_convert = partial(self._try_to_convert, cv.utils.dumpRange)
+        for convertible in ((10, 20), [-1, 3], np.array([10, 24]), Range(-4, 6)):
+            expected = 'range: (s={}, e={})'.format(*convertible)
+            actual = try_to_convert(convertible)
+            self.assertEqual(expected, actual,
+                             msg=get_conversion_error_msg(convertible, expected, actual))
+
+    def test_parse_to_range_not_convertible(self):
+        for not_convertible in ((1, ), [40, ], np.array([1, 4, 6]), {'a': 1, 'b': 40},
+                                (1.5, 13.5), [3, 6.7], np.array([6.3, 2.1]), '14, 4'):
+            with self.assertRaises((TypeError), msg=get_no_exception_msg(not_convertible)):
+                _ = cv.utils.dumpRange(not_convertible)
+
 
 class SamplesFindFile(NewOpenCVTests):