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-rw-r--r--gerber/rs274x.py33
-rw-r--r--gerber/utils.py6
2 files changed, 38 insertions, 1 deletions
diff --git a/gerber/rs274x.py b/gerber/rs274x.py
index 7b3a3b9..86785bc 100644
--- a/gerber/rs274x.py
+++ b/gerber/rs274x.py
@@ -21,6 +21,7 @@
import copy
import json
import re
+import sys
try:
from cStringIO import StringIO
@@ -30,6 +31,7 @@ except(ImportError):
from .gerber_statements import *
from .primitives import *
from .cam import CamFile, FileSettings
+from .utils import sq_distance
def read(filename):
@@ -548,7 +550,7 @@ class GerberParser(object):
else:
i = 0 if stmt.i is None else stmt.i
j = 0 if stmt.j is None else stmt.j
- center = (start[0] + i, start[1] + j)
+ center = self._find_center(start, end, (i, j))
if self.region_mode == 'off':
self.primitives.append(Arc(start, end, center, self.direction, self.apertures[self.aperture], quadrant_mode=self.quadrant_mode, level_polarity=self.level_polarity, units=self.settings.units))
else:
@@ -579,6 +581,35 @@ class GerberParser(object):
self.primitives.append(primitive)
self.x, self.y = x, y
+
+ def _find_center(self, start, end, offsets):
+ """
+ In single quadrant mode, the offsets are always positive, which means there are 4 possible centers.
+ The correct center is the only one that results in an arc with sweep angle of less than or equal to 90 degrees
+ """
+
+ if self.quadrant_mode == 'single-quadrant':
+
+ # The Gerber spec says single quadrant only has one possible center, and you can detect
+ # based on the angle. But for real files, this seems to work better - there is usually
+ # only one option that makes sense for the center (since the distance should be the same
+ # from start and end). Find the center that makes the most sense
+ sqdist_diff_min = sys.maxint
+ center = None
+ for factors in [(1, 1), (1, -1), (-1, 1), (-1, -1)]:
+
+ test_center = (start[0] + offsets[0] * factors[0], start[1] + offsets[1] * factors[1])
+
+ sqdist_start = sq_distance(start, test_center)
+ sqdist_end = sq_distance(end, test_center)
+
+ if abs(sqdist_start - sqdist_end) < sqdist_diff_min:
+ center = test_center
+ sqdist_diff_min = abs(sqdist_start - sqdist_end)
+
+ return center
+ else:
+ return (start[0] + offsets[0], start[1] + offsets[1])
def _evaluate_aperture(self, stmt):
self.aperture = stmt.d
diff --git a/gerber/utils.py b/gerber/utils.py
index 72bf2d1..41d264a 100644
--- a/gerber/utils.py
+++ b/gerber/utils.py
@@ -297,3 +297,9 @@ def nearly_equal(point1, point2, ndigits = 6):
'''Are the points nearly equal'''
return round(point1[0] - point2[0], ndigits) == 0 and round(point1[1] - point2[1], ndigits) == 0
+
+def sq_distance(point1, point2):
+
+ diff1 = point1[0] - point2[0]
+ diff2 = point1[1] - point2[1]
+ return diff1 * diff1 + diff2 * diff2