Added python interface to threshold_image() and partition_pixels().

tools/python/src/image.cpp

@@ -26,6 +26,62 @@ string print_rgb_pixel_repr(const rgb_pixel& p)
     return sout.str();
 }
 
+// ----------------------------------------------------------------------------------------
+
+template <typename T>
+numpy_image<unsigned char> py_threshold_image2(
+    const numpy_image<T>& in_img,
+    typename pixel_traits<T>::basic_pixel_type thresh
+)
+{
+    numpy_image<unsigned char> out_img;
+    threshold_image(in_img, out_img);
+    return out_img;
+}
+
+template <typename T>
+numpy_image<unsigned char> py_threshold_image(
+    const numpy_image<T>& in_img
+)
+{
+    numpy_image<unsigned char> out_img;
+    threshold_image(in_img, out_img);
+    return out_img;
+}
+
+// ----------------------------------------------------------------------------------------
+
+template <typename T>
+typename pixel_traits<T>::basic_pixel_type py_partition_pixels (
+    const numpy_image<T>& img
+)
+{
+    return partition_pixels(img);
+}
+
+template <typename T>
+py::tuple py_partition_pixels2 (
+    const numpy_image<T>& img,
+    int num_thresholds
+)
+{
+    DLIB_CASSERT(1 <= num_thresholds && num_thresholds <= 6);
+
+    typename pixel_traits<T>::basic_pixel_type t1,t2,t3,t4,t5,t6;
+
+    switch(num_thresholds)
+    {
+        case 1: partition_pixels(img,t1); return py::make_tuple(t1);
+        case 2: partition_pixels(img,t1,t2); return py::make_tuple(t1,t2);
+        case 3: partition_pixels(img,t1,t2,t3); return py::make_tuple(t1,t2,t3);
+        case 4: partition_pixels(img,t1,t2,t3,t4); return py::make_tuple(t1,t2,t3,t4);
+        case 5: partition_pixels(img,t1,t2,t3,t4,t5); return py::make_tuple(t1,t2,t3,t4,t5);
+        case 6: partition_pixels(img,t1,t2,t3,t4,t5,t6); return py::make_tuple(t1,t2,t3,t4,t5,t6);
+    }
+    DLIB_CASSERT(false, "This should never happen.");
+}
+
+
 // ----------------------------------------------------------------------------------------
 
 void bind_image_classes(py::module& m)
@@ -37,4 +93,55 @@ void bind_image_classes(py::module& m)
         .def_readwrite("red", &rgb_pixel::red)
         .def_readwrite("green", &rgb_pixel::green)
         .def_readwrite("blue", &rgb_pixel::blue);
+
+    const char* docs = "Thresholds img and returns the result.  Pixels in img with grayscale values >= partition_pixels(img) \n" 
+              "have an output value of 255 and all others have a value of 0.";
+    m.def("threshold_image", &py_threshold_image<unsigned char>, py::arg("img") );
+    m.def("threshold_image", &py_threshold_image<uint16_t>, py::arg("img") );
+    m.def("threshold_image", &py_threshold_image<uint32_t>, py::arg("img") );
+    m.def("threshold_image", &py_threshold_image<float>, py::arg("img") );
+    m.def("threshold_image", &py_threshold_image<double>, py::arg("img") );
+    m.def("threshold_image", &py_threshold_image<rgb_pixel>,docs, py::arg("img") );
+
+    docs = "Thresholds img and returns the result.  Pixels in img with grayscale values >= thresh \n"
+              "have an output value of 255 and all others have a value of 0.";
+    m.def("threshold_image", &py_threshold_image2<unsigned char>, py::arg("img"), py::arg("thresh") );
+    m.def("threshold_image", &py_threshold_image2<uint16_t>, py::arg("img"), py::arg("thresh") );
+    m.def("threshold_image", &py_threshold_image2<uint32_t>, py::arg("img"), py::arg("thresh") );
+    m.def("threshold_image", &py_threshold_image2<float>, py::arg("img"), py::arg("thresh") );
+    m.def("threshold_image", &py_threshold_image2<double>, py::arg("img"), py::arg("thresh") );
+    m.def("threshold_image", &py_threshold_image2<rgb_pixel>,docs, py::arg("img"), py::arg("thresh") );
+
+
+    docs = 
+"Finds a threshold value that would be reasonable to use with \n\
+threshold_image(img, threshold).  It does this by finding the threshold that \n\
+partitions the pixels in img into two groups such that the sum of absolute \n\
+deviations between each pixel and the mean of its group is minimized.";
+    m.def("partition_pixels", &py_partition_pixels<rgb_pixel>, py::arg("img") );
+    m.def("partition_pixels", &py_partition_pixels<unsigned char>, py::arg("img") );
+    m.def("partition_pixels", &py_partition_pixels<uint16_t>, py::arg("img") );
+    m.def("partition_pixels", &py_partition_pixels<uint32_t>, py::arg("img") );
+    m.def("partition_pixels", &py_partition_pixels<float>, py::arg("img") );
+    m.def("partition_pixels", &py_partition_pixels<double>,docs, py::arg("img") );
+
+    docs = 
+"This version of partition_pixels() finds multiple partitions rather than just \n\
+one partition.  It does this by first partitioning the pixels just as the \n\
+above partition_pixels(img) does.  Then it forms a new image with only pixels \n\
+>= that first partition value and recursively partitions this new image. \n\
+However, the recursion is implemented in an efficient way which is faster than \n\
+explicitly forming these images and calling partition_pixels(), but the \n\
+output is the same as if you did.  For example, suppose you called \n\
+[t1,t2,t2] = partition_pixels(img).  Then we would have: \n\
+   - t1 == partition_pixels(img) \n\
+   - t2 == partition_pixels(an image with only pixels with values >= t1 in it) \n\
+   - t3 == partition_pixels(an image with only pixels with values >= t2 in it)" ;
+    m.def("partition_pixels", &py_partition_pixels2<rgb_pixel>, py::arg("img"), py::arg("num_thresholds") );
+    m.def("partition_pixels", &py_partition_pixels2<unsigned char>, py::arg("img"), py::arg("num_thresholds") );
+    m.def("partition_pixels", &py_partition_pixels2<uint16_t>, py::arg("img"), py::arg("num_thresholds") );
+    m.def("partition_pixels", &py_partition_pixels2<uint32_t>, py::arg("img"), py::arg("num_thresholds") );
+    m.def("partition_pixels", &py_partition_pixels2<float>, py::arg("img"), py::arg("num_thresholds") );
+    m.def("partition_pixels", &py_partition_pixels2<double>,docs, py::arg("img"), py::arg("num_thresholds") );
 }
+

tools/python/test/test_numpy_returns.py

@@ -26,6 +26,22 @@ def get_test_face_chip():
     rgb_img, shape = get_test_image_and_shape()
     return dlib.get_face_chip(rgb_img, shape)
 
+def test_partition_pixels():
+    truth = (102, 159, 181);
+    img, shape = get_test_image_and_shape()
+
+    assert(dlib.partition_pixels(img) == truth[0])
+    assert(dlib.partition_pixels(img,3) == truth)
+
+    # Call all these versions of this mainly to make sure binding to
+    # various image types works.
+    assert(dlib.partition_pixels(img[:,:,0]) == 125)
+    assert(dlib.partition_pixels(img[:,:,0].astype('float32')) == 125)
+    assert(dlib.partition_pixels(img[:,:,0].astype('float64')) == 125)
+    assert(dlib.partition_pixels(img[:,:,0].astype('uint16')) == 125)
+    assert(dlib.partition_pixels(img[:,:,0].astype('uint32')) == 125)
+
+
 # The tests below will be skipped if Numpy is not installed
 @pytest.mark.skipif(not utils.is_numpy_installed(), reason="requires numpy")
 def test_get_face_chip():
@@ -63,4 +79,4 @@ def test_regression_issue_1220_get_face_chips():
     count = sys.getrefcount(face_chips)
     assert count == 2
     count = sys.getrefcount(face_chips[0])
-    assert count == 2
+    assert count == 2