From 50c2165f37764dfca581da941e623409a36ee831 Mon Sep 17 00:00:00 2001
From: Raphael <raphael.sturgis@gmail.com>
Date: Mon, 21 Mar 2022 16:52:39 +0100
Subject: [PATCH] slopes greater than 1 for bresenham algorithm
---
skais/tests/utils/test_geometry.py | 7 +++++
skais/utils/geometry.py | 44 ++++++++++++++++++++----------
2 files changed, 37 insertions(+), 14 deletions(-)
diff --git a/skais/tests/utils/test_geometry.py b/skais/tests/utils/test_geometry.py
index 91b0907..7a0b76d 100644
--- a/skais/tests/utils/test_geometry.py
+++ b/skais/tests/utils/test_geometry.py
@@ -18,6 +18,13 @@ class TestGeometry(unittest.TestCase):
self.assertListEqual(result, expected)
+
+ def test_bresenham_inverted_2(self):
+ result = bresenham(16, 4, 3, 9)
+ expected = [(3, 9), (4, 9), (5, 8), (6, 8), (7, 7), (8, 7), (9, 7), (10, 6), (11, 6), (12, 6), (13, 5), (14, 5),
+ (15, 4), (16, 4)]
+ self.assertListEqual(result, expected)
+
def test_bresenham_same_line(self):
result = bresenham(3, 4, 10, 4)
expected = [(3, 4), (4, 4), (5, 4), (6, 4), (7, 4), (8, 4), (9, 4), (10, 4)]
diff --git a/skais/utils/geometry.py b/skais/utils/geometry.py
index 78521b2..885aa42 100644
--- a/skais/utils/geometry.py
+++ b/skais/utils/geometry.py
@@ -3,28 +3,44 @@ def bresenham(x1, y1, x2, y2):
tmp = x2
x2 = x1
x1 = tmp
- if y1 > y2:
+
+
tmp = y2
y2 = y1
y1 = tmp
+
+ dx = int(x2 - x1)
+ dy = int(y2 - y1)
+
+ sx = sy = 1
+ if dx < 0:
+ sx = -1
+ if dy < 0:
+ sy = -1
+
+ x = x1
+ y = y1
pixels = [(x1, y1)]
- if x1 == x2:
- x = x1
- for y in range(y1 + 1, y2 + 1):
+ if abs(dx) > abs(dy): # slope < 1
+ p = (2 * abs(dy)) - abs(dx)
+
+ for x in range(x1 + 1, x2 + 1):
+ if p < 0:
+ p += 2 * abs(dy)
+ else:
+ y += sy
+ p += (2 * abs(dy)) - (2 * abs(dx))
pixels.append((x, y))
- else:
- a = 2*(y2 - y1)
- b = a - 2*(x2 - x1)
- p = a - (x2 - x1)
-
- y = y1
- for x in range(x1+1, x2+1):
+ else: # slope >= 1
+ p = (2 * abs(dx)) - abs(dy)
+ for y in range(y1 + 1, y2 + 1):
if p < 0:
- p += a
+ p += 2 * abs(dx)
else:
- y += 1
- p += b
+ x += sx
+ p += (2 * abs(dx)) - (2 * abs(dy))
pixels.append((x, y))
+
return pixels
--
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