Request for help with Image color space conversion

[ttest]

Hello,

I'm working on an image processing project using the Python Imaging
Library along with numpy.  Right now, I'm trying to build a speedy
script for converting whole images between the RGB and the HSV (a.k.a.
HSB) color spaces.  Unfortunately, the code I've made so far runs
dreadfully slow with even moderate-sized images.

I'm under the impression that the crux of the problem is the fact that
PIL's point method operates on only one band at a time, and to do a
proper color space conversion, you need information about all three
bands in a particular problem.  This has forced me to do an awkward
work-around where the image data is loaded into a numpy array
(1600x1200x3), and a dinky for-loop run runs through the array picking
up RGB values, converting to HSV, and dumping the results back into
another array.

How can I make this more efficient?

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from PIL import Image
from PIL import TiffImagePlugin
from scipy.misc import pilutil
import numpy
import colorsys

def myrgbtohsv(r,g,b):
    '''A wrapper for the colorsys function rgb_to_hsv
    that takes r,g,b values between 0 and 255
    (standard pixel value range in most of my single-band imaging
operations)
    and returns the corresponding 255-scaled h,s,v values'''
    tr = r/255.0
    tg = g/255.0
    tb = b/255.0
    ur,ug,ub = colorsys.rgb_to_hsv(tr,tg,tb)
    pr = int(round(ur,0))*255
    pg = int(round(ug,0))*255
    pb = int(round(ub,0))*255
    return pr,pg,pb

def rgbarrtohsvarr(pilarray):
    '''Takes an 3d numpy ndarray loaded with a RGB PIL image and
converts
    a copy of the contents to 255-scaled HSV array.

    Returns the converted copy of the array.
    '''
    arrt = pilarray.copy()
    r,c,d = arrt.shape
    hsvarray = numpy.zeros((r,c,d))

    print out
    for i in range(0,r):
        for j in range(0,c):
            localrgb = (arrt[i,j,0],arrt[i,j,1],arrt[i,j,2])
            (lh,ls,lv) = rgbtohsv(localrgb)
            hsvarray[i,j,0],hsvarray[i,j,1],hsvarray[i,j,2]= lh,ls,lv

    return hsvarray

im = Image.open(r'C:\test.tif')
arr = pilutil.fromimage(im)
out = rgbarrtohsvarr(arr)

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