Add spiral example

examples/helper/spiral

@@ -0,0 +1,32 @@
+#! /usr/bin/env python3
+import numpy as np
+from com.dtmilano.android.viewclient import ViewClient
+
+def toint(n):
+    return n.item()
+
+def npint(a):
+    return np.round(a).astype(int)
+
+def spiral(t):
+    a = 0.5  # Controls the tightness of the spiral
+    b = 0.5  # Controls the spacing between turns
+    g = 40 # Factor
+    dx = 400 # Delta x
+    dy = 600 # Delta y
+    x = g * a * t * np.cos(t + b) + dx
+    y = g * a * t * np.sin(t + b) + dy
+    return list(zip(map(toint, npint(x)), map(toint, npint(y))))
+
+# get helper
+helper = ViewClient.view_client_helper()
+
+# generate values for the parameter t
+t = np.linspace(0, 4 * np.pi, 100)
+
+# calculate (x, y) coordinates
+segments = spiral(t)
+
+# assume google keep is open so we can see it drawing
+# see spiral.gif
+helper.ui_device.swipe(segments=segments, segment_steps=3)