Add an image_size attribute to both Connectors and Cables

It is a list containing minimum width and minimum height of the
image cell. To obtain more available space in the image cell,
this size must be set greater than the natural size of the image.

src/wireviz/DataClasses.py

@@ -20,6 +20,7 @@ class Connector:
     pincount: Optional[int] = None
     image: Optional[str] = None
     image_scale: Optional[str] = "FALSE"
+    image_size: List[Any] = field(default_factory=list)
     caption: Optional[str] = None
     notes: Optional[str] = None
     pinlabels: List[Any] = field(default_factory=list)
@@ -96,6 +97,7 @@ class Cable:
     shield: bool = False
     image: Optional[str] = None
     image_scale: Optional[str] = "FALSE"
+    image_size: List[Any] = field(default_factory=list)
     caption: Optional[str] = None
     notes: Optional[str] = None
     colors: List[Any] = field(default_factory=list)

src/wireviz/wv_helper.py

@@ -58,11 +58,22 @@ def nested_html_table(rows):
 def html_image(node):
     if not node.image:
         return None
-    return f'''<tdX{' sides="TLR"' if node.caption else ''}><img scale="{node.image_scale}" src="{node.image}"/>'''
+    return f'''<tdX{' sides="TLR"' if node.caption else ''}{html_size_attr(node.image_size)}>''' \
+           f'''<img scale="{node.image_scale}" src="{node.image}"/>'''
 
 def html_caption(node):
     return f'''<tdX{' sides="LRB"' if node.image else ''}>{html_line_breaks(node.caption)}''' if node.caption else None
 
+def html_size_attr(size):
+    # Return Graphviz HTML attributes to specify minimum size of a TABLE or TD object
+    # size: List of values where only these are used:
+    # - First value is minimum width of object in points, an int value in the range 1-65535. (Default 0 = none)
+    # - Second value is minimum height of the object in points, an int value in the range 1-65535. (Default 0 = none)
+    if not size or not isinstance(size, list):
+        return ''
+    return ((f' width="{size[0]}"' if len(size) > 0 and size[0] else '')
+        + (f' height="{size[1]}"' if len(size) > 1 and size[1] else ''))
+
 
 def expand(yaml_data):
     # yaml_data can be: