Set fill and stroke opacity from color alpha

Thanks Chris Buergi for the initial patch.

CHANGELOG.rst

@@ -8,6 +8,8 @@ Unreleased
 
 - dropped support for Python 3.6 and added official support for Python 3.10.
 - improved support for scientific notation in paths (#277)
+- if some path has a color with alpha value, it also sets the default fill or
+  stroke opacity of the resulting object.
 
 1.1.0 (2021-04-10)
 ------------------

svglib/svglib.py

@@ -368,7 +368,7 @@ def convertColor(self, svgAttr):
             if color is None:
                 # Test if text is a predefined color constant
                 try:
-                    color = getattr(colors, text)
+                    color = getattr(colors, text).clone()
                 except AttributeError:
                     pass
         if color is None:
@@ -1386,6 +1386,18 @@ def applyStyleOnShape(self, shape, node, only_explicit=False):
                     if svgAttrValue == '':
                         if only_explicit:
                             continue
+                        if (
+                            svgAttrName == 'fill-opacity'
+                            and getattr(shape, 'fillColor', None) is not None
+                            and getattr(shape.fillColor, 'alpha', 1) != 1
+                        ):
+                            svgAttrValue = shape.fillColor.alpha
+                        elif (
+                            svgAttrName == 'stroke-opacity'
+                            and getattr(shape, 'strokeColor', None) is not None
+                            and getattr(shape.strokeColor, 'alpha', 1) != 1
+                        ):
+                            svgAttrValue = shape.strokeColor.alpha
                         else:
                             svgAttrValue = defaults[index]
                     if svgAttrValue == "currentColor":

tests/test_basic.py

@@ -436,6 +436,22 @@ def test_fillopacity(self):
         ''')))
         assert drawing.contents[0].contents[0].fillColor == colors.Color(0, 0, 0, 0)
 
+    def test_fillcolor_alpha_set_fillopacity(self):
+        converter = svglib.Svg2RlgShapeConverter(None)
+        node = etree.XML('<polygon fill="#ff000080"/>')
+        poly = Polygon()
+        converter.applyStyleOnShape(poly, node)
+        assert poly.fillOpacity == 128 / 255
+        assert poly.strokeOpacity == 1
+
+    def test_strokecolor_alpha_set_strokeopacity(self):
+        converter = svglib.Svg2RlgShapeConverter(None)
+        node = etree.XML('<polygon stroke="#cccccca0"/>')
+        poly = Polygon()
+        converter.applyStyleOnShape(poly, node)
+        assert poly.fillOpacity == 1
+        assert poly.strokeOpacity == 160 / 255
+
     def test_fillrule(self):
         converter = svglib.Svg2RlgShapeConverter(None)
         node = etree.XML('<polygon fill-rule="evenodd"/>')