added rgb2hsv color conversion

scikits/image/color/colorconv.py

@@ -0,0 +1,63 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+
+"""
+:author: Nicolas Pinto, 2009
+:license: modified BSD
+"""
+
+from __future__ import division
+
+__all__ = ["rgb2hsv"]
+__docformat__ = "restructuredtext en"
+
+import numpy as np
+
+def rgb2hsv(rgb):
+
+    """
+    RGB to HSV color space conversion    
+    """
+
+    if type(rgb) != np.ndarray:
+        raise TypeError, "the input array 'rgb' must be a numpy.ndarray"
+
+    if rgb.ndim != 3 or rgb.shape[2] != 3:
+        msg = "the input array 'rgb' must be have a shape == (.,.,3))"
+        raise ValueError, msg
+              
+    arr = rgb.astype("float32")
+    out = np.empty_like(arr)
+    
+    # -- V channel
+    out_v = arr.max(-1)
+
+    # -- S channel
+    delta = arr.ptp(-1)
+    out_s = delta / out_v
+    out_s[delta==0] = 0
+
+    # -- H channel
+    # red is max
+    idx = (arr[:,:,0] == out_v) 
+    out[idx, 0] = (arr[idx, 1] - arr[idx, 2]) / delta[idx]
+
+    # green is max
+    idx = (arr[:,:,1] == out_v) 
+    out[idx, 0] = 2. + (arr[idx, 2] - arr[idx, 0] ) / delta[idx]
+
+    # blue is max
+    idx = (arr[:,:,2] == out_v) 
+    out[idx, 0] = 4. + (arr[idx, 0] - arr[idx, 1] ) / delta[idx]
+    out_h = (out[:,:,0] / 6.) % 1.
+
+    # -- output
+    out[:,:,0] = out_h
+    out[:,:,1] = out_s
+    out[:,:,2] = out_v
+
+    # remove NaN
+    out[np.isnan(out)] = 0
+
+    return out
+

scikits/image/color/tests/test_colorconv.py

@@ -0,0 +1,48 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+
+"""
+:author: Nicolas Pinto, 2009
+:license: modified BSD
+"""
+
+from os import path
+
+import numpy as np
+from numpy.testing import *
+
+from scikits.image.io import imread
+from scikits.image.color import (
+    rgb2hsv,
+    )
+
+from scikits.image import data
+
+import colorsys
+
+class TestColorconv(TestCase):
+
+    img_rgb = imread(path.join(data.MY_PATH, 'color.png'))
+    img_grayscale = imread(path.join(data.MY_PATH, 'camera.png'))
+
+    def test_rgb2hsv_conversion(self):
+        rgb = self.img_rgb.astype("float32")[::16, ::16]
+        hsv = rgb2hsv(rgb).reshape(-1, 3)
+        # ground truth from colorsys
+        gt = np.array([colorsys.rgb_to_hsv(pt[0], pt[1], pt[2])
+                       for pt in rgb.reshape(-1, 3)]
+                      )
+        assert_almost_equal(hsv, gt)
+
+    def test_rgb2hsv_error_grayscale(self):        
+        self.assertRaises(ValueError, rgb2hsv, self.img_grayscale)
+
+    def test_rgb2hsv_error_one_element(self):
+        self.assertRaises(ValueError, rgb2hsv, self.img_rgb[0,0])
+
+    def test_rgb2hsv_error_list(self):
+        self.assertRaises(TypeError, rgb2hsv, [self.img_rgb[0,0]])
+
+if __name__ == "__main__":
+    run_module_suite()
+