Initial public commit

misc/pylib/fontbuild/convertCurves.py

@@ -0,0 +1,102 @@
+#! /usr/bin/env python
+#
+# Copyright 2015 Google Inc. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""
+Converts a cubic bezier curve to a quadratic spline with 
+exactly two off curve points.
+
+"""
+
+import numpy
+from numpy import array,cross,dot
+from fontTools.misc import bezierTools
+from robofab.objects.objectsRF import RSegment
+
+def replaceSegments(contour, segments):
+    while len(contour):
+        contour.removeSegment(0)
+    for s in segments:
+        contour.appendSegment(s.type, [(p.x, p.y) for p in s.points], s.smooth)
+    
+def calcIntersect(a,b,c,d):
+    numpy.seterr(all='raise')
+    e = b-a
+    f = d-c
+    p = array([-e[1], e[0]])
+    try:
+        h = dot((a-c),p) / dot(f,p)
+    except:
+        print a,b,c,d
+        raise
+    return c + dot(f,h)
+
+def simpleConvertToQuadratic(p0,p1,p2,p3):
+    p = [array(i.x,i.y) for i in [p0,p1,p2,p3]]
+    off = calcIntersect(p[0],p[1],p[2],p[3])
+
+# OFFCURVE_VECTOR_CORRECTION = -.015
+OFFCURVE_VECTOR_CORRECTION = 0
+
+def convertToQuadratic(p0,p1,p2,p3):
+    # TODO: test for accuracy and subdivide further if needed
+    p = [(i.x,i.y) for i in [p0,p1,p2,p3]]
+    # if p[0][0] == p[1][0] and p[0][0] == p[2][0] and p[0][0] == p[2][0] and p[0][0] == p[3][0]:
+    #     return (p[0],p[1],p[2],p[3]) 
+    # if p[0][1] == p[1][1] and p[0][1] == p[2][1] and p[0][1] == p[2][1] and p[0][1] == p[3][1]:
+    #     return (p[0],p[1],p[2],p[3])     
+    seg1,seg2 = bezierTools.splitCubicAtT(p[0], p[1], p[2], p[3], .5)
+    pts1 = [array([i[0], i[1]]) for i in seg1]
+    pts2 = [array([i[0], i[1]]) for i in seg2]
+    on1 = seg1[0]
+    on2 = seg2[3]
+    try:
+        off1 = calcIntersect(pts1[0], pts1[1], pts1[2], pts1[3])
+        off2 = calcIntersect(pts2[0], pts2[1], pts2[2], pts2[3])
+    except:
+        return (p[0],p[1],p[2],p[3])
+    off1 = (on1 - off1) * OFFCURVE_VECTOR_CORRECTION + off1
+    off2 = (on2 - off2) * OFFCURVE_VECTOR_CORRECTION + off2
+    return (on1,off1,off2,on2)
+
+def cubicSegmentToQuadratic(c,sid):
+    
+    segment = c[sid]
+    if (segment.type != "curve"):
+        print "Segment type not curve"
+        return
+    
+    #pSegment,junk = getPrevAnchor(c,sid)
+    pSegment = c[sid-1] #assumes that a curve type will always be proceeded by another point on the same contour
+    points = convertToQuadratic(pSegment.points[-1],segment.points[0],
+                                segment.points[1],segment.points[2])
+    return RSegment(
+        'qcurve', [[int(i) for i in p] for p in points[1:]], segment.smooth)
+
+def glyphCurvesToQuadratic(g):
+
+    for c in g:
+        segments = []
+        for i in range(len(c)):
+            s = c[i]
+            if s.type == "curve":
+                try:
+                    segments.append(cubicSegmentToQuadratic(c, i))
+                except Exception:
+                    print g.name, i
+                    raise
+            else:
+                segments.append(s)
+        replaceSegments(c, segments)