import numpy as np
import holoviews as hv
from holoviews import opts

hv.extension('matplotlib')

data = np.sin(np.mgrid[0:100,0:100][1]/10.0)
data[np.arange(40, 60), np.arange(20, 40)] = -1
data[np.arange(40, 50), np.arange(70, 80)] = -3    
(hv.Image(data) * hv.Box(-0.2, 0, 0.25 ) * hv.Box(-0, 0, (0.4,0.9))).opts(
    opts.Box(color='red', linewidth=5),
    opts.Image(cmap='gray'))

data = np.sin(np.mgrid[0:100,0:100][1]/10.0)
data[np.arange(30, 70), np.arange(30, 70)] = -3
box = hv.Box(-0, 0, 0.25, aspect=3, orientation=-np.pi/4)

(hv.Image(data) * box).opts(
    opts.Box(color='purple', linewidth=5),
    opts.Image(cmap='gray'))