title: make subplots from an astronomical fits image
body: <p>I have a set of <code>RGB</code> Images and I made a <code>RGB</code> fits image with <code>aplpy</code> and I also overlaid some contours on the image but I would like to cut the image and make small fits images where I would see the peaks of contour.</p>
  
  <pre><code>import aplpy
  import atpy
  from pyavm import AVM
  import asciitable
  import matplotlib
  import matplotlib.pyplot as plt
  from matplotlib.colors import LogNorm,BoundaryNorm
  import montage_wrapper
  from astropy.io import fits
  import pyfits
  from astropy import wcs
  fitsfile = 'rgb.fits'
  fitsfile_2d = 'rgb_2d.fits'
  pngfile = 'rgb_arcsinh_contour.png'
  
  figfile = 'rgb.png'
  w = wcs.WCS(naxis=2)
  
  # Set up an "Airy's zenithal" projection
  # Vector properties may be set with Python lists, or Numpy arrays
  w.wcs.crpix = [5.70000000E+03, 3.05000000E+03]
  w.wcs.cdelt = np.array([-6.611111263E-05, 6.611111263E-05])
  w.wcs.crval = [23.166667, -7.666667]
  w.wcs.ctype = ["RA---TAN", "DEC--TAN"]
  w.wcs.cunit =["deg","deg"]
  
  # Print out all of the contents of the WCS object
  w.wcs.print_contents()
  
  # Some pixel coordinates of interest.
  pixcrd = np.array([[0,0],[24,38],[45,98]], np.float_)
  
  # Convert pixel coordinates to world coordinates
  world = w.wcs_pix2world(pixcrd, 1)
  print world
  
  # Convert the same coordinates back to pixel coordinates.
  pixcrd2 = w.wcs_world2pix(world, 1)
  print pixcrd2
  
  # These should be the same as the original pixel coordinates, modulo
  # some floating-point error.
  assert np.max(np.abs(pixcrd - pixcrd2)) &lt; 1e-6
  
  # Now, write out the WCS object as a FITS header
  header = w.to_header()
  hdu = pyfits.open(fitsfile)
  # header is an astropy.io.fits.Header object.  We can use it to create a new
  # PrimaryHDU and write it to a file.
  hdu = fits.PrimaryHDU(header=header)
  
  
  # make rgb image
  aplpy.make_rgb_image(fitsfile, pngfile,
                       vmin_r=-0.005, vmax_r=0.2,
                       vmin_g=-0.02, vmax_g=0.1,
                       vmin_b=-0.02,vmax_b=0.04,
                       embed_avm_tags=False)
  
  # make a figure
  img = aplpy.FITSFigure(fitsfile_2d)
  img.show_rgb(pngfile)
  img.set_nan_color('white')
  standard_setup(img)  
  </code></pre>
  
  <p>How could I produce subplots from given coordinates of the image with a given size ?</p>