Merge pull request #216 from meerk40t/issue214

Fixes Issue #214

svgelements/svgelements.py

@@ -4787,7 +4787,12 @@ def _real_minmax(self, v):
                 if 0 < r2 < 1:
                     local_extremizers.append(r2)
         else:
-            local_extremizers.append(0.5)
+            c = a[1] - a[0]
+            b = 2 * (a[0] - 2*a[1] + a[2])
+            if b != 0:
+                r0 = -c/b
+                if 0 < r0 < 1:
+                    local_extremizers.append(r0)
         local_extrema = [self.point(t)[v] for t in local_extremizers]
         return min(local_extrema), max(local_extrema)
 

test/test_cubic_bezier.py

@@ -1,16 +1,20 @@
+import random
 import unittest
 from random import *
 
 from svgelements import *
 
 
 def get_random_cubic_bezier():
-    return CubicBezier((random() * 50, random() * 50), (random() * 50, random() * 50),
-                       (random() * 50, random() * 50), (random() * 50, random() * 50))
+    return CubicBezier(
+        (random() * 50, random() * 50),
+        (random() * 50, random() * 50),
+        (random() * 50, random() * 50),
+        (random() * 50, random() * 50),
+    )
 
 
 class TestElementCubicBezierLength(unittest.TestCase):
-
     def test_cubic_bezier_length(self):
         n = 100
         error = 0
@@ -25,18 +29,20 @@ def test_cubic_bezier_length(self):
 
 
 class TestElementCubicBezierPoint(unittest.TestCase):
-
     def test_cubic_bezier_point_start_stop(self):
         import numpy as np
+
         for _ in range(1000):
             b = get_random_cubic_bezier()
             self.assertEqual(b.start, b.point(0))
             self.assertEqual(b.end, b.point(1))
-            self.assertTrue(np.all(np.array([list(b.start), list(b.end)])
-                                   == b.npoint([0, 1])))
+            self.assertTrue(
+                np.all(np.array([list(b.start), list(b.end)]) == b.npoint([0, 1]))
+            )
 
     def test_cubic_bezier_point_implementations_match(self):
         import numpy as np
+
         for _ in range(1000):
             b = get_random_cubic_bezier()
 
@@ -50,3 +56,21 @@ def test_cubic_bezier_point_implementations_match(self):
             for p, p1, p2 in zip(pos, v1, v2):
                 self.assertEqual(b.point(p), Point(p1))
                 self.assertEqual(Point(p1), Point(p2))
+
+    def test_cubic_bounds_issue_214(self):
+        cubic = CubicBezier(0, -2 - 3j, -1 - 4j, -3j)
+        bbox = cubic.bbox()
+        self.assertLess(bbox[1], -3)
+
+    def test_cubic_bounds_issue_214_random(self):
+        for i in range(100):
+            a = random() * 5
+            b = random() * 5
+            c = random() * 5
+            d = a - 3 * b + 3 * c
+            cubic1 = CubicBezier(a, b, c, d)
+            bbox1 = cubic1.bbox()
+            cubic2 = CubicBezier(a, b, c, d + 1e-11)
+            bbox2 = cubic2.bbox()
+            for a, b in zip(bbox1, bbox2):
+                self.assertAlmostEqual(a, b, delta=1e-5)