Implement 6 transformations as static methods

Author: ima18h

variations.py

@@ -16,3 +16,33 @@ def transform(self):
     def linear(x, y):
         return x, y
 
+    @staticmethod
+    def handkerchief(x, y):
+        r = np.sqrt(x**2 + y**2)
+        theta = np.arctan2(x, y)
+        return r * np.sin(theta + r), r * np.cos(theta - r)
+
+    @staticmethod
+    def swirl(x, y):
+        r = np.sqrt(x ** 2 + y ** 2)
+        return x * np.sin(r**2) - y * np.cos(r**2), x * np.cos(r**2) + y * np.sin(r**2)
+
+    @staticmethod
+    def disc(x, y):
+        r = np.sqrt(x ** 2 + y ** 2)
+        theta = np.arctan2(x, y)
+        c = theta / np.pi
+        return c * np.sin(np.pi * r), c * np.cos(np.pi * r)
+
+    @staticmethod
+    def eyefish(x, y):
+        r = np.sqrt(x ** 2 + y ** 2)
+        c = 2 / (r + 1)
+        return c * x, c * y
+
+    @staticmethod
+    def horseshoe(x, y):
+        r = np.sqrt(x ** 2 + y ** 2)
+        c = 1 / r
+        return c * ((x-y) * (x+y)), c * 2 * x*y
+