how to use 'extent' in matplotlib.pyplot.imshow

Question

I managed to plot my data and would like to add a background image (map) to it. Data is plotted by the long/lat values and I have the long/lat values for the image\'s three

Answer 1

Here's an example based on http://matplotlib.org/examples/pylab_examples/image_demo3.html showing use of extent.

#!/usr/bin/env python
from pylab import *
try:
    from PIL import Image
except ImportError, exc:
    raise SystemExit("PIL must be installed to run this example")

import matplotlib.cbook as cbook

datafile = cbook.get_sample_data('ada.png')
h = Image.open(datafile)
dpi = rcParams['figure.dpi']
figsize = h.size[0]/dpi, h.size[1]/dpi

figure(figsize=figsize)
ax = axes([0,0,1,1], frameon=False)
ax.set_axis_off()
ax.set_xlim(0,2)
ax.set_ylim(0,2)
im = imshow(h, origin='upper',extent=[-2,4,-2,4])  # axes zoom in on portion of image
im2 = imshow(h, origin='upper',extent=[0,.5,0,.5]) # image is a small inset on axes

show()

If you don't set your axis limits, they become your extents & then don't seem to have any effect.