Extract patches from an image

import os
from optparse import OptionParser
import cPickle
import skimage
import numpy as np
from scipy import misc
from distutils.dir_util import mkpath

def loadImage(imgpath):
    try:
    	im = misc.imread(imgpath)
    	return im
    except:
    	print "Can't open image. Check image again: " + imgpath

def extractPatches(im, outpath, window_shape=(13,13, 3),stride=3):
    nr, nc, ncolor = im.shape
    patches = skimage.util.view_as_windows(im, window_shape, stride)
    nR, nC, t, H, W, C = patches.shape
    nWindow = nR * nC
    patches =  np.reshape(patches, (nWindow, H, W, C))
    patches = patches.astype(np.float16, copy=False)
    #pathces = np.asarray(patches, dtype=np.float16)
    return patches

if __name__ == '__main__':
    parser = OptionParser()
    parser.add_option('-i', '--imgpath', dest='imgpath', help='path of input image')
    parser.add_option('-o', '--outpath', dest='outpath', help="path of output")
    (options, args) = parser.parse_args()

    im = loadImage(options.imgpath)
    patches = extractPatches(im, options.outpath)

    if not os.path.isdir(options.outpath):
        mkpath(options.outpath)

    imname = os.path.basename(options.imgpath).split('.')[0]
    outfile = options.outpath + imname + "_patches.dump"

    f = open(outfile, 'wb')
    cPickle.dump(patches, f, protocol=2)
    f.close()

Thanks for this! You saved me a few hours of headache.