[varLib.mutator] Implement IUP

Lib/fontTools/varLib/mutator.py

@@ -11,6 +11,94 @@ from fontTools.varLib import _GetCoordinates, _SetCoordinates
 from fontTools.varLib.models import VariationModel, supportScalar, normalizeLocation
 import os.path
 
+
+def _iup_segment(coords, rc1, rd1, rc2, rd2):
+	# rc1 = reference coord 1
+	# rd1 = reference delta 1
+	out_arrays = [None, None]
+	for j in 0,1:
+		out_arrays[j] = out = []
+		x1, x2, d1, d2 = rc1[j], rc2[j], rd1[j], rd2[j]
+
+
+		if x1 == x2:
+			n = len(coords)
+			if d1 == d2:
+				out.extend([d1]*n)
+			else:
+				out.extend([0]*n)
+			continue
+
+		if x1 > x2:
+			x1, x2 = x2, x1
+			d1, d2 = d2, d1
+
+		# x1 < x2
+		scale = (d2 - d1) / (x2 - x1)
+		for pair in coords:
+			x = pair[j]
+
+			if x <= x1:
+				d = d1
+			elif x >= x2:
+				d = d2
+			else:
+				# Interpolate
+				d = d1 + (x - x1) * scale
+
+			out.append(d)
+
+	return zip(*out_arrays)
+
+def _iup_contour(delta, coords):
+	assert len(delta) == len(coords)
+	if None not in delta:
+		return delta
+
+	n = len(delta)
+	# indices of points with explicit deltas
+	indices = [i for i,v in enumerate(delta) if v is not None]
+	if not indices:
+		# All deltas are None.  Return 0,0 for all.
+		return [(0,0)]*n
+
+	out = []
+	it = iter(indices)
+	start = next(it)
+	if start != 0:
+		# Initial segment that wraps around
+		i1, i2, ri1, ri2 = 0, start, start, indices[-1]
+		out.extend(_iup_segment(coords[i1:i2], coords[ri1], delta[ri1], coords[ri2], delta[ri2]))
+	out.append(delta[start])
+	for end in it:
+		if end - start > 1:
+			i1, i2, ri1, ri2 = start+1, end, start, end
+			out.extend(_iup_segment(coords[i1:i2], coords[ri1], delta[ri1], coords[ri2], delta[ri2]))
+		out.append(delta[end])
+		start = end
+	if start != n-1:
+		# Final segment that wraps around
+		i1, i2, ri1, ri2 = start+1, n, start, indices[0]
+		out.extend(_iup_segment(coords[i1:i2], coords[ri1], delta[ri1], coords[ri2], delta[ri2]))
+
+	assert len(delta) == len(out), (len(delta), len(out))
+	return out
+
+def _iup_delta(delta, coords, ends):
+	assert sorted(ends) == ends and len(coords) == (ends[-1]+1 if ends else 0) + 4
+	n = len(coords)
+	ends = ends + [n-4, n-3, n-2, n-1]
+	out = []
+	start = 0
+	for end in ends:
+		end += 1
+		contour = _iup_contour(delta[start:end], coords[start:end])
+		out.extend(contour)
+		start = end
+
+	return out
+
+
 def main(args=None):
 
 	if args is None:
@@ -59,6 +147,7 @@ def main(args=None):
 				if origCoords is None:
 					origCoords,control = _GetCoordinates(varfont, glyphname)
 					endPts = control[1] if control[0] >= 1 else list(range(len(control[1])))
+				delta = _iup_delta(delta, origCoords, endPts)
 				# TODO Do IUP / handle None items
 			coordinates += GlyphCoordinates(delta) * scalar
 		_SetCoordinates(varfont, glyphname, coordinates)