Python k4a api: Put ctypes structs inside k4atypes.py.

Arrange import methods so that:
1. "import k4a" will expose all visible symbols in the module k4atypes.py.
2. "from k4a import *" will work the same way as "import k4a".

To see all symbols in k4atypes.py, use "import k4a.k4atypes".
This is considered to be a development or debug way of importing symbols.
Users are encouraged to use "import k4a".

src/python/k4a/src/k4a/__init__.py

@@ -1 +1,7 @@
-from .k4atypes import * 
+from ._bindings import *
+
+# We want "import k4a" to import all symbols in k4atypes.py under k4a.<x>.
+from .k4atypes import *
+
+del _bindings
+del k4atypes

src/python/k4a/src/k4a/_bindings/__init__.py

@@ -1,4 +1,19 @@
+import os.path
+import sys
+import ctypes
 
 
+# Load the k4a.dll.
+lib_dir = os.path.join(os.path.dirname(os.path.dirname(__file__)), '_libs')
+try:
+    _k4a_dll = ctypes.CDLL(os.path.join(lib_dir, 'k4a.dll'))
+except Exception as e:
+    try:
+        _k4a_dll = ctypes.CDLL(os.path.join(lib_dir, 'k4a.so'))
+    except Exception as ee:
+        print("Failed to load library", e, ee)
+        sys.exit(1)
 
-
+# Define symbols that will be exported with "from .bindings import *".
+__all__ = [
+]

src/python/k4a/src/k4a/_bindings/_k4a.py

@@ -0,0 +1,90 @@
+'''k4atypes.py
+
+Defines Python _ctypes equivalent functions to those defined in k4a.h. 
+
+Credit given to hexops's github contribution for the
+_ctypes.Structure definitions and _ctypes function bindings.
+https://github.com/hexops/Azure-Kinect-Python
+'''
+
+import ctypes as _ctypes
+
+# Either k4a library is installed, or user is running from the repo
+# Either way, the expectation is that we can import the from k4a.k4atypes.
+try:
+    from k4a.k4atypes import *
+except Exception as e:
+    import os
+    import sys
+    sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.dirname(__file__))))
+    from k4a.k4atypes import *
+
+
+# Map _ctypes symbols to functions in the k4a.dll.
+# The dll should have been loaded in __init__.py which is run when this subpackage is imported.
+
+
+#K4A_EXPORT k4a_result_t k4a_device_open(uint32_t index, k4a_device_t *device_handle);
+k4a_device_open = _k4a_dll.k4a_device_open
+k4a_device_open.restype=k4a_result_t
+k4a_device_open.argtypes=(_ctypes.c_uint32, _ctypes.POINTER(k4a_device_t))
+
+
+#K4A_EXPORT k4a_result_t k4a_device_start_cameras(k4a_device_t device_handle, const k4a_device_configuration_t *config);
+k4a_device_start_cameras = _k4a_dll.k4a_device_start_cameras
+k4a_device_start_cameras.restype=_ctypes.c_int
+k4a_device_start_cameras.argtypes=(k4a_device_t, _ctypes.POINTER(k4a_device_configuration_t))
+
+
+"""
+K4A_EXPORT k4a_result_t k4a_device_get_calibration(k4a_device_t device_handle,
+                                                   const k4a_depth_mode_t depth_mode,
+                                                   const k4a_color_resolution_t color_resolution,
+                                                   k4a_calibration_t *calibration);
+"""
+k4a_device_get_calibration = _k4a_dll.k4a_device_get_calibration
+k4a_device_get_calibration.restype=_ctypes.c_int
+k4a_device_get_calibration.argtypes=(k4a_device_t, _ctypes.c_int, _ctypes.c_int, _ctypes.POINTER(k4a_calibration_t))
+
+
+"""
+K4A_EXPORT k4a_wait_result_t k4a_device_get_capture(k4a_device_t device_handle,
+                                                    k4a_capture_t *capture_handle,
+                                                    int32_t timeout_in_ms);
+"""
+k4a_device_get_capture = _k4a_dll.k4a_device_get_capture
+k4a_device_get_capture.restype=_ctypes.c_int
+k4a_device_get_capture.argtypes=(k4a_device_t, _ctypes.POINTER(k4a_capture_t), _ctypes.c_int32)
+
+
+#K4A_EXPORT void k4a_capture_release(k4a_capture_t capture_handle);
+k4a_capture_release = _k4a_dll.k4a_capture_release
+k4a_capture_release.argtypes=(k4a_capture_t,)
+
+
+#K4A_EXPORT void k4a_image_release(k4a_image_t image_handle);
+k4a_image_release = _k4a_dll.k4a_image_release
+k4a_image_release.argtypes=(k4a_image_t,)
+
+
+#K4A_EXPORT void k4a_device_stop_cameras(k4a_device_t device_handle);
+k4a_device_stop_cameras = _k4a_dll.k4a_device_stop_cameras
+k4a_device_stop_cameras.argtypes=(k4a_device_t,)
+
+
+#K4A_EXPORT void k4a_device_close(k4a_device_t device_handle);
+k4a_device_close = _k4a_dll.k4a_device_close
+k4a_device_close.argtypes=(k4a_device_t,)
+
+
+#K4A_EXPORT k4a_buffer_result_t k4a_device_get_serialnum(k4a_device_t device_handle, char *serial_number, size_t *serial_number_size);
+k4a_device_get_serialnum = _k4a_dll.k4a_device_get_serialnum
+k4a_device_get_capture.restype=k4a_buffer_result_t
+k4a_device_close.argtypes=(k4a_device_t, _ctypes.c_char_p, _ctypes.c_ulonglong)
+
+
+# Define symbols that will be exported with "from _k4a import *".
+__all__ = [
+]
+
+del _ctypes