Added barnsley_fern.py

Python/fractals/barnsley_fern.py

@@ -0,0 +1,42 @@
+import random
+from PIL import Image
+
+
+class BarnsleyFern(object):
+    def __init__(self, img_width, img_height, paint_color=(0, 150, 0),
+                 bg_color=(255, 255, 255)):
+        self.img_width, self.img_height = img_width, img_height
+        self.paint_color = paint_color
+        self.x, self.y = 0, 0
+        self.age = 0
+
+        self.fern = Image.new('RGB', (img_width, img_height), bg_color)
+        self.pix = self.fern.load()
+        self.pix[self.scale(0, 0)] = paint_color
+
+    def scale(self, x, y):
+        h = (x + 2.182)*(self.img_width - 1)/4.8378
+        k = (9.9983 - y)*(self.img_height - 1)/9.9983
+        return h, k
+
+    def transform(self, x, y):
+        rand = random.uniform(0, 100)
+        if rand < 1:
+            return 0, 0.16*y
+        elif 1 <= rand < 86:
+            return 0.85*x + 0.04*y, -0.04*x + 0.85*y + 1.6
+        elif 86 <= rand < 93:
+            return 0.2*x - 0.26*y, 0.23*x + 0.22*y + 1.6
+        else:
+            return -0.15*x + 0.28*y, 0.26*x + 0.24*y + 0.44
+
+    def iterate(self, iterations):
+        for _ in range(iterations):
+            self.x, self.y = self.transform(self.x, self.y)
+            self.pix[self.scale(self.x, self.y)] = self.paint_color
+        self.age += iterations
+
+fern = BarnsleyFern(500, 500)
+fern.iterate(1000000)
+fern.fern.show()
+