how to increase contrast of image in python code example

Example 1: change colorbar size and place python

plt.colorbar(im,fraction=0.046, pad=0.04)

Example 2: how to increase button size in fltter

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