The width and the height can be specified as pixel values (eg "23" or "23px") or percentages (eg "23%"). They are both optional; if not provided the browser will use CSS rules to size the image.
! External Images and the ''_canonical_uri'' field
When used to display tiddler-based images, the image widget operates in two distinct modes:
* If the ''_canonical_uri'' field is present then it is used as the ''src'' attribute of the generated `<img>` element and the ''text'' field is ignored
* Without the ''_canonical_uri'' field, the image widget generates an `<img>` element that embeds the image data directly using a `data:` URI.