rename radial gradient Paint.Affine attribute to Transform

as suggested by Peter Constable in
https://github.com/PeterConstable/OT_Drafts/blob/master/COLR_V1/COLRv1formats_rev3.md#paintformat3-table-conicalradial-gradient

Lib/fontTools/colorLib/builder.py

@@ -423,7 +423,7 @@ def buildRadialGradientPaint(
     c1: _PointTuple,
     r0: _ScalarInput,
     r1: _ScalarInput,
-    affine: Optional[_AffineInput] = None,
+    transform: Optional[_AffineInput] = None,
 ) -> ot.Paint:
 
     self = ot.Paint()
@@ -435,9 +435,9 @@ def buildRadialGradientPaint(
         setattr(self, f"y{i}", _to_variable_int(y))
         setattr(self, f"r{i}", _to_variable_int(r))
 
-    if affine is not None and not isinstance(affine, ot.Affine2x2):
-        affine = buildAffine2x2(*affine)
-    self.Affine = affine
+    if transform is not None and not isinstance(transform, ot.Affine2x2):
+        transform = buildAffine2x2(*transform)
+    self.Transform = transform
 
     return self
 

Lib/fontTools/ttLib/tables/otData.py

@@ -1640,6 +1640,6 @@ otData = [
 		('VarInt16', 'x1', None, None, ''),
 		('VarInt16', 'y1', None, None, ''),
 		('VarUInt16', 'r1', None, None, ''),
-		('LOffsetTo(Affine2x2)', 'Affine', None, None, 'Offset (from beginning of Paint table) to Affine2x2 subtable.'),
+		('LOffsetTo(Affine2x2)', 'Transform', None, None, 'Offset (from beginning of Paint table) to Affine2x2 subtable.'),
 	]),
 ]

Tests/colorLib/builder_test.py

@@ -337,7 +337,7 @@ def test_buildRadialGradientPaint():
     assert (gradient.x1, gradient.y1) == c1
     assert gradient.r0 == r0
     assert gradient.r1 == r1
-    assert gradient.Affine is None
+    assert gradient.Transform is None
 
     gradient = builder.buildRadialGradientPaint({"stops": color_stops}, c0, c1, r0, r1)
     assert gradient.ColorLine.Extend == builder.ExtendMode.PAD
@@ -345,14 +345,14 @@ def test_buildRadialGradientPaint():
 
     matrix = builder.buildAffine2x2(2.0, 0.0, 0.0, 2.0)
     gradient = builder.buildRadialGradientPaint(
-        color_line, c0, c1, r0, r1, affine=matrix
+        color_line, c0, c1, r0, r1, transform=matrix
     )
-    assert gradient.Affine == matrix
+    assert gradient.Transform == matrix
 
     gradient = builder.buildRadialGradientPaint(
-        color_line, c0, c1, r0, r1, affine=(2.0, 0.0, 0.0, 2.0)
+        color_line, c0, c1, r0, r1, transform=(2.0, 0.0, 0.0, 2.0)
     )
-    assert gradient.Affine == matrix
+    assert gradient.Transform == matrix
 
 
 def test_buildLayerV1Record():

Tests/ttLib/tables/C_O_L_R_test.py

@@ -268,12 +268,12 @@ COLR_V1_XML = [
     '          <x1 value="10"/>',
     '          <y1 value="11"/>',
     '          <r1 value="12"/>',
-    "          <Affine>",
+    "          <Transform>",
     '            <xx value="-13.0"/>',
     '            <xy value="14.0"/>',
     '            <yx value="15.0"/>',
     '            <yy value="-17.0"/>',
-    "          </Affine>",
+    "          </Transform>",
     "        </Paint>",
     "      </LayerV1Record>",
     "    </LayerV1List>",