how to increase container size in html code example

Example 1: how to change the height of an image in html

<img src="smiley.gif" alt="Smiley face" height="42" width="42">

Example 2: how to increase button size in fltter

ButtonTheme(
  minWidth: 200.0,
  height: 100.0,
  child: RaisedButton(
    onPressed: () {},
    child: Text("test"),
  ),
);