add ndarray-json converter

snippets/ndarray_to_json.py

@@ -0,0 +1,60 @@
+import sys
+
+use_ulab = False
+
+try:
+    from ubinascii import a2b_base64 as b64encode
+    from ubinascii import hexlify
+    import ujson as json
+    from ulab import numpy as np
+    use_ulab = True
+except:
+    from base64 import b64encode
+    import json
+    import numpy as np
+    from numpy.lib.format import dtype_to_descr
+
+def ulab_dtype_to_descr(dtype):
+    desc = '<'
+    if sys.byteorder == 'little':
+        desc = '>'
+
+    if dtype == ord('B'):
+        desc = desc + 'u1'
+    elif dtype == ord('b'):
+        desc = desc + 'i1'
+    elif dtype == ord('H'):
+        desc = desc + 'u2'
+    elif dtype == ord('h'):
+        desc = desc + 'i2'
+    elif dtype == ord('d'):
+        desc = desc + 'f8'
+    elif dtype == ord('f'):
+        desc = desc + 'f4'
+    elif dtype == ord('c'):
+        desc = desc + 'c16'
+        if np.array([1], dtype=np.float).itemsize == 4:
+            desc = desc + 'c8'
+
+    return desc
+
+def ndarray_to_json(obj, b64=False):
+    if not isinstance(obj, np.ndarray):
+         raise TypeError('input argument must be an ndarray')
+
+    if use_ulab:
+        dtype_desciptor = ulab_dtype_to_descr(obj.dtype)
+    else:
+        dtype_desciptor = dtype_to_descr(obj.dtype)
+
+    if not b64:
+        data = hexlify(obj.tobytes())
+
+    return json.dumps({'__numpy__': data, 'dtype': dtype_desciptor, 'shape': obj.shape})
+
+
+dtypes = (np.uint8, np.int8, np.uint16, np.int16, np.float)
+
+for dtype in dtypes:
+    ndarray = np.array([1, 2, 3], dtype=dtype)
+    print(ndarray_to_json(ndarray))