Support image.bgcolor to enable adapting to image colors

docs/syntax.md

@@ -424,6 +424,7 @@ image:
   src: <path>        # path to the image file
   # optional parameters:
   caption: <str>     # text to display below the image
+  bgcolor: <color>   # Background color of entry in diagram component box
   width: <int>       # range: 1~65535; unit: points
   height: <int>      # range: 1~65535; unit: points
   # if only one dimension (width/height) is specified, the image is scaled proportionally.

src/wireviz/DataClasses.py

@@ -75,6 +75,7 @@ class Image:
     width: Optional[int] = None
     height: Optional[int] = None
     fixedsize: Optional[bool] = None
+    bgcolor: Optional[Color] = None
     # Contents of the text cell <td> just below the image cell:
     caption: Optional[MultilineHypertext] = None
     # See also HTML doc at https://graphviz.org/doc/info/shapes.html#html

src/wireviz/wv_gv_html.py

@@ -59,11 +59,12 @@ def html_image(image):
      <td{html}</td>
     </tr></table>
    '''
-    return f'''<tdX{' sides="TLR"' if image.caption else ''}{html}'''
+    return f'''<tdX{' sides="TLR"' if image.caption else ''}{html_bgcolor_attr(image.bgcolor)}{html}'''
 
 def html_caption(image):
     from wireviz.DataClasses import Image
-    return f'<tdX sides="BLR">{html_line_breaks(image.caption)}' if image and image.caption else None
+    return (f'<tdX sides="BLR"{html_bgcolor_attr(image.bgcolor)}>{html_line_breaks(image.caption)}'
+                if image and image.caption else None)
 
 def html_size_attr(image):
     from wireviz.DataClasses import Image