epub converter: fix colors

- add rgba
- fix converting to nearest white if not white

src/util/color_reader.py

@@ -44,9 +44,10 @@ def get_hex_color_name(color):
 
 def str2color_name(s: str):
     if 'rgb' in s:
-        s = s.replace('rgb', '').replace('(', '').replace(')', '')
+        rgb_str = 'rgba' if ('rgba' in s) else 'rgb'
+        s = s.replace(rgb_str, '').replace('(', '').replace(')', '')
         try:
-            rgb = [int(x) for x in s.split(',')]
+            rgb = [int(x) for x in s.split(',')[:3]]
             rgb = tuple(rgb)
         except ValueError:
             return ''
@@ -57,6 +58,11 @@ def str2color_name(s: str):
 
     elif '#' in s:
         name = get_hex_color_name(s)
+        if (name == 'white') and (s.lower() not in ['#ffffff', '#fff']):
+            return 'gray'
+        if name == 'grey':
+            return 'gray'
+
         return name
 
     elif s in html4_hex_to_names.items():