Fix from picosvg #76

src/nanoemoji/color_glyph.py

@@ -198,22 +198,22 @@ def _parse_radial_gradient(grad_el, shape_bbox, view_box, upem):
 }
 
 
-def _color_stop(stop_el) -> ColorStop:
+def _color_stop(stop_el, shape_opacity=1.0) -> ColorStop:
     offset = _number_or_percentage(stop_el.attrib.get("offset", "0"))
     color = Color.fromstring(stop_el.attrib.get("stop-color", "black"))
     opacity = _number_or_percentage(stop_el.attrib.get("stop-opacity", "1"))
-    color = color._replace(alpha=color.alpha * opacity)
+    color = color._replace(alpha=color.alpha * opacity * shape_opacity)
     return ColorStop(stopOffset=offset, color=color)
 
 
-def _common_gradient_parts(el):
+def _common_gradient_parts(el, shape_opacity=1.0):
     spread_method = el.attrib.get("spreadMethod", "pad").upper()
     if spread_method not in Extend.__members__:
         raise ValueError(f"Unknown spreadMethod {spread_method}")
 
     return {
         "extend": Extend.__members__[spread_method],
-        "stops": tuple(_color_stop(stop) for stop in el),
+        "stops": tuple(_color_stop(stop, shape_opacity) for stop in el),
     }
 
 
@@ -237,7 +237,7 @@ def _paint(self, shape):
             el = self.picosvg.resolve_url(shape.fill, "*")
 
             grad_type, grad_type_parser = _GRADIENT_INFO[etree.QName(el).localname]
-            grad_args = _common_gradient_parts(el)
+            grad_args = _common_gradient_parts(el, shape.opacity)
             try:
                 grad_args.update(
                     grad_type_parser(

tests/color_glyph_test.py

@@ -217,6 +217,32 @@ def _round_gradient_coordinates(paint, prec=6):
                 )
             },
         ),
+        # Shape with opacity, should apply to gradient colors
+        # See https://github.com/googlefonts/picosvg/issues/76
+        (
+            "gradient_opacity.svg",
+            {
+                PaintLinearGradient(
+                    stops=(
+                        ColorStop(stopOffset=0.1, color=Color.fromstring("blue", alpha=0.4)),
+                        ColorStop(stopOffset=0.9, color=Color.fromstring("cyan", alpha=0.4 * 0.8)),
+                    ),
+                    p0=Point(200.0, 800.0),
+                    p1=Point(800.0, 800.0),
+                ),
+                PaintRadialGradient(
+                    stops=(
+                        ColorStop(stopOffset=0.1, color=Color.fromstring("red", alpha=0.5),),
+                        ColorStop(stopOffset=0.9, color=Color.fromstring("yellow", alpha=0.5 * 0.8),),
+                    ),
+                    c0=Point(x=500.0, y=400.0),
+                    c1=Point(x=500.0, y=400.0),
+                    r0=0.0,
+                    r1=300.0,
+                    affine2x2=(1.0, 0.0, 0.0, -0.333333),
+                )
+            },
+        ),
     ],
 )
 def test_paint_from_shape(svg_in, expected_paints):