1 files changed, 20 insertions, 0 deletions
diff --git a/Lib/fontTools/varLib/models.py b/Lib/fontTools/varLib/models.py
index 8ea1432a..653b75ff 100644
--- a/Lib/fontTools/varLib/models.py
+++ b/Lib/fontTools/varLib/models.py
@@ -339,6 +339,26 @@ class VariationModel(object):
 		return self.interpolateFromDeltasAndScalars(deltas, scalars)
 
 
+def piecewiseLinearMap(v, mapping):
+	keys = mapping.keys()
+	if not keys:
+		return v
+	if v in keys:
+		return mapping[v]
+	k = min(keys)
+	if v < k:
+		return v + mapping[k] - k
+	k = max(keys)
+	if v > k:
+		return v + mapping[k] - k
+	# Interpolate
+	a = max(k for k in keys if k < v)
+	b = min(k for k in keys if k > v)
+	va = mapping[a]
+	vb = mapping[b]
+	return va + (vb - va) * (v - a) / (b - a)
+
+
 def main(args):
 	from fontTools import configLogger