[Matplotlib-users] using patch's to get image masks

[Graeme O'K. <gj...@ne...>]

Hi,

is there a way to get an image of a patch? I'd like to use patches to  
display Regions Of Interest and
also use then use them as masks on the image for subsequent region  
based analysis.

regards,

Graeme

===== code snippet ======

#!/usr/bin/env python

import wasabi, ugm
import pylab

#
# 22-frames * 90-slices * 128-y * 128-x
#
dy  = ugm.ugm('dy22.img')

#
# grab the 20th frame
#
vol = dy.vol([20])

#
# returns a series of roi's that are defined as a set of vertices of  
a polygon
# eg.
# roi['cerebellum'] = numarray.array([[x0,y0], [x1,y1], ...., [xN, yN]])
# roi['caudate'] ...
#
roi = wasabi.roi('p2873s0_HAW_emdy22.xml')

pylab.figure()
ax = pylab.gca()
n = 0
col = 'rgbcmyk'
p = []
for fld in roi.keys() :
#
# draw the polygon regions as patches with transparency
#
     p.append(ax.fill(roi[fld][:,0], roi[fld][:,1], col[n],  
alpha=0.5, linewidth=0))
     pylab.hold(True)
     n += 1
#end for
pylab.imshow(vol[45,:,:], cmap = pylab.cm.hot, origin = 'lower')
print p

#
# is there a way to 'get' an array of pixels set in the patches p[0],  
p[1] so that they can be used as masks
# on the image.
#