From 032d0cd785a979da59e90c1064a868cd252618e4 Mon Sep 17 00:00:00 2001
From: Ralf Gommers <rgommers@Ralf-Gommerss-iMac.local>
Date: Mon, 19 Oct 2009 10:38:44 +0200
Subject: [PATCH 01/16] Change import to form used everywhere else.

---
 scikits/image/color/tests/test_colorconv.py | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/scikits/image/color/tests/test_colorconv.py b/scikits/image/color/tests/test_colorconv.py
index 1d8ecc17..3dbc027d 100644
--- a/scikits/image/color/tests/test_colorconv.py
+++ b/scikits/image/color/tests/test_colorconv.py
@@ -6,7 +6,7 @@
 :license: modified BSD
 """
 
-from os import path
+import os.path
 
 import numpy as np
 from numpy.testing import *
@@ -22,8 +22,8 @@ import colorsys
 
 class TestColorconv(TestCase):
 
-    img_rgb = imread(path.join(data_dir, 'color.png'))
-    img_grayscale = imread(path.join(data_dir, 'camera.png'))
+    img_rgb = imread(os.path.join(data_dir, 'color.png'))
+    img_grayscale = imread(os.path.join(data_dir, 'camera.png'))
 
     def test_rgb2hsv_conversion(self):
         rgb = self.img_rgb.astype("float32")[::16, ::16]
@@ -34,7 +34,7 @@ class TestColorconv(TestCase):
                       )
         assert_almost_equal(hsv, gt)
 
-    def test_rgb2hsv_error_grayscale(self):        
+    def test_rgb2hsv_error_grayscale(self):
         self.assertRaises(ValueError, rgb2hsv, self.img_grayscale)
 
     def test_rgb2hsv_error_one_element(self):

From 6c80fa6a5514f71999f80b768ebffbdf604d617a Mon Sep 17 00:00:00 2001
From: Ralf Gommers <rgommers@Ralf-Gommerss-iMac.local>
Date: Mon, 19 Oct 2009 10:48:09 +0200
Subject: [PATCH 02/16] Add documentation for rgb2hsv.

---
 scikits/image/color/colorconv.py | 36 +++++++++++++++++++++++++-------
 1 file changed, 29 insertions(+), 7 deletions(-)

diff --git a/scikits/image/color/colorconv.py b/scikits/image/color/colorconv.py
index cd3c3b63..c12791cf 100644
--- a/scikits/image/color/colorconv.py
+++ b/scikits/image/color/colorconv.py
@@ -14,9 +14,31 @@ __docformat__ = "restructuredtext en"
 import numpy as np
 
 def rgb2hsv(rgb):
+    """RGB to HSV color space conversion.
 
-    """
-    RGB to HSV color space conversion    
+    Parameters
+    ----------
+    rgb : ndarray
+        The image in RGB format, in a 3-D array of shape (.., .., 3).
+
+    Returns
+    -------
+    out : ndarray
+        The image in HSV format, in a 3-D array of shape (.., .., 3).
+
+    Raises
+    ------
+    ValueError
+        If `rgb` is not a 3-D array of shape (.., .., 3).
+
+    Examples
+    --------
+    >>> import os
+    >>> from scikits.image import data_dir
+    >>> from scikits.image.io import imread
+
+    >>> lena = imread(os.path.join(data_dir, 'lena.png'))
+    >>> lena_hsv = color.rgb2hsv(lena)
     """
 
     if type(rgb) != np.ndarray:
@@ -25,10 +47,10 @@ def rgb2hsv(rgb):
     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)
 
@@ -39,15 +61,15 @@ def rgb2hsv(rgb):
 
     # -- H channel
     # red is max
-    idx = (arr[:,:,0] == out_v) 
+    idx = (arr[:,:,0] == out_v)
     out[idx, 0] = (arr[idx, 1] - arr[idx, 2]) / delta[idx]
 
     # green is max
-    idx = (arr[:,:,1] == out_v) 
+    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) 
+    idx = (arr[:,:,2] == out_v)
     out[idx, 0] = 4. + (arr[idx, 0] - arr[idx, 1] ) / delta[idx]
     out_h = (out[:,:,0] / 6.) % 1.
 

From 1657a4d1b83bd61af4093357c224da07f8f5549f Mon Sep 17 00:00:00 2001
From: Ralf Gommers <rgommers@Ralf-Gommerss-iMac.local>
Date: Mon, 19 Oct 2009 14:34:00 +0200
Subject: [PATCH 03/16] Implement hsv2rgb.

---
 scikits/image/color/colorconv.py            | 60 ++++++++++++++++++++-
 scikits/image/color/tests/test_colorconv.py | 24 +++++++++
 2 files changed, 83 insertions(+), 1 deletion(-)

diff --git a/scikits/image/color/colorconv.py b/scikits/image/color/colorconv.py
index c12791cf..9130738a 100644
--- a/scikits/image/color/colorconv.py
+++ b/scikits/image/color/colorconv.py
@@ -8,7 +8,7 @@
 
 from __future__ import division
 
-__all__ = ["rgb2hsv"]
+__all__ = ['rgb2hsv', 'hsv2rgb']
 __docformat__ = "restructuredtext en"
 
 import numpy as np
@@ -83,3 +83,61 @@ def rgb2hsv(rgb):
 
     return out
 
+
+def hsv2rgb(hsv):
+    """HSV to RGB color space conversion.
+
+    Parameters
+    ----------
+    hsv : ndarray
+        The image in HSV format, in a 3-D array of shape (.., .., 3).
+
+    Returns
+    -------
+    out : ndarray
+        The image in RGB format, in a 3-D array of shape (.., .., 3).
+
+    Raises
+    ------
+    ValueError
+        If `hsv` is not a 3-D array of shape (.., .., 3).
+
+    Examples
+    --------
+    >>> import os
+    >>> from scikits.image import data_dir
+    >>> from scikits.image.io import imread
+
+    >>> lena = imread(os.path.join(data_dir, 'lena.png'))
+    >>> lena_hsv = rgb2hsv(lena)
+    >>> lena_rgb = hsv2rgb(lena_hsv)
+    """
+
+    if type(hsv) != np.ndarray:
+        raise TypeError, "the input array 'hsv' must be a numpy.ndarray"
+
+    if hsv.ndim != 3 or hsv.shape[2] != 3:
+        msg = "the input array 'hsv' must be have a shape == (.,.,3))"
+        raise ValueError, msg
+
+    arr = hsv.astype("float32")
+
+    hi = np.floor(arr[:,:,0] * 6)
+    f = arr[:,:,0] * 6 - hi
+    p = arr[:,:,2] * (1 - arr[:,:,1])
+    q = arr[:,:,2] * (1 - f * arr[:,:,1])
+    t = arr[:,:,2] * (1 - (1 - f) * arr[:,:,1])
+    v = arr[:,:,2]
+
+    hi = np.dstack([hi, hi, hi]).astype("uint8") % 6
+    out = np.choose(hi, [np.dstack((v, t, p)),
+                         np.dstack((q, v, p)),
+                         np.dstack((p, v, t)),
+                         np.dstack((p, q, v)),
+                         np.dstack((t, p, v)),
+                         np.dstack((v, p, q))])
+
+    # remove NaN
+    out[np.isnan(out)] = 0
+
+    return out
diff --git a/scikits/image/color/tests/test_colorconv.py b/scikits/image/color/tests/test_colorconv.py
index 3dbc027d..f40dcec5 100644
--- a/scikits/image/color/tests/test_colorconv.py
+++ b/scikits/image/color/tests/test_colorconv.py
@@ -14,17 +14,20 @@ from numpy.testing import *
 from scikits.image.io import imread
 from scikits.image.color import (
     rgb2hsv,
+    hsv2rgb,
     )
 
 from scikits.image import data_dir
 
 import colorsys
 
+
 class TestColorconv(TestCase):
 
     img_rgb = imread(os.path.join(data_dir, 'color.png'))
     img_grayscale = imread(os.path.join(data_dir, 'camera.png'))
 
+    # RGB to HSV
     def test_rgb2hsv_conversion(self):
         rgb = self.img_rgb.astype("float32")[::16, ::16]
         hsv = rgb2hsv(rgb).reshape(-1, 3)
@@ -43,6 +46,27 @@ class TestColorconv(TestCase):
     def test_rgb2hsv_error_list(self):
         self.assertRaises(TypeError, rgb2hsv, [self.img_rgb[0,0]])
 
+
+    # HSV to RGB
+    def test_hsv2rgb_conversion(self):
+        rgb = self.img_rgb.astype("float32")[::16, ::16]
+        # create HSV image with colorsys
+        hsv = np.array([colorsys.rgb_to_hsv(pt[0], pt[1], pt[2])
+                        for pt in rgb.reshape(-1, 3)]).reshape(rgb.shape)
+        # convert back to RGB and compare with original.
+        # float32 -> relative precision about 1e-6
+        assert_almost_equal(rgb, hsv2rgb(hsv), decimal=4)
+
+    def test_hsv2rgb_error_grayscale(self):
+        self.assertRaises(ValueError, hsv2rgb, self.img_grayscale)
+
+    def test_hsv2rgb_error_one_element(self):
+        self.assertRaises(ValueError, hsv2rgb, self.img_rgb[0,0])
+
+    def test_hsv2rgb_error_list(self):
+        self.assertRaises(TypeError, hsv2rgb, [self.img_rgb[0,0]])
+
+
 if __name__ == "__main__":
     run_module_suite()
 

From 6097565337daf0efbb5fee23608a79b932c23f0d Mon Sep 17 00:00:00 2001
From: Ralf Gommers <rgommers@Ralf-Gommerss-iMac.local>
Date: Mon, 19 Oct 2009 14:45:33 +0200
Subject: [PATCH 04/16] Add note on loss of precision.

---
 scikits/image/color/colorconv.py            | 18 ++++++++++++++++++
 scikits/image/color/tests/test_colorconv.py |  2 +-
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/scikits/image/color/colorconv.py b/scikits/image/color/colorconv.py
index 9130738a..065f1d31 100644
--- a/scikits/image/color/colorconv.py
+++ b/scikits/image/color/colorconv.py
@@ -31,6 +31,15 @@ def rgb2hsv(rgb):
     ValueError
         If `rgb` is not a 3-D array of shape (.., .., 3).
 
+    Notes
+    -----
+    Conversion between RGB and HSV color spaces results in some loss of
+    precision, due to integer arithmetic and rounding [1]_.
+
+    References
+    ----------
+    .. [1] http://en.wikipedia.org/wiki/HSL_and_HSV
+
     Examples
     --------
     >>> import os
@@ -102,6 +111,15 @@ def hsv2rgb(hsv):
     ValueError
         If `hsv` is not a 3-D array of shape (.., .., 3).
 
+    Notes
+    -----
+    Conversion between RGB and HSV color spaces results in some loss of
+    precision, due to integer arithmetic and rounding [1]_.
+
+    References
+    ----------
+    .. [1] http://en.wikipedia.org/wiki/HSL_and_HSV
+
     Examples
     --------
     >>> import os
diff --git a/scikits/image/color/tests/test_colorconv.py b/scikits/image/color/tests/test_colorconv.py
index f40dcec5..67f641bb 100644
--- a/scikits/image/color/tests/test_colorconv.py
+++ b/scikits/image/color/tests/test_colorconv.py
@@ -54,7 +54,7 @@ class TestColorconv(TestCase):
         hsv = np.array([colorsys.rgb_to_hsv(pt[0], pt[1], pt[2])
                         for pt in rgb.reshape(-1, 3)]).reshape(rgb.shape)
         # convert back to RGB and compare with original.
-        # float32 -> relative precision about 1e-6
+        # relative precision for RGB -> HSV roundtrip is about 1e-6
         assert_almost_equal(rgb, hsv2rgb(hsv), decimal=4)
 
     def test_hsv2rgb_error_grayscale(self):

From 844f14bca0dd07aeb7cbdb140142f891dc22cbab Mon Sep 17 00:00:00 2001
From: Ralf Gommers <rgommers@Ralf-Gommerss-iMac.local>
Date: Mon, 19 Oct 2009 15:14:21 +0200
Subject: [PATCH 05/16] Extract the type and shape checks into a common
 function.

---
 scikits/image/color/colorconv.py | 32 ++++++++++++++------------------
 1 file changed, 14 insertions(+), 18 deletions(-)

diff --git a/scikits/image/color/colorconv.py b/scikits/image/color/colorconv.py
index 065f1d31..4016c65b 100644
--- a/scikits/image/color/colorconv.py
+++ b/scikits/image/color/colorconv.py
@@ -13,6 +13,18 @@ __docformat__ = "restructuredtext en"
 
 import numpy as np
 
+
+def _prepare_colorarray(arr, dtype="float32"):
+    """Check the shape of the array, and give it the requested type"""
+    if type(arr) != np.ndarray:
+        raise TypeError, "the input array must be a numpy.ndarray"
+
+    if arr.ndim != 3 or arr.shape[2] != 3:
+        msg = "the input array must be have a shape == (.,.,3))"
+        raise ValueError, msg
+
+    return arr.astype(dtype)
+
 def rgb2hsv(rgb):
     """RGB to HSV color space conversion.
 
@@ -49,15 +61,7 @@ def rgb2hsv(rgb):
     >>> lena = imread(os.path.join(data_dir, 'lena.png'))
     >>> lena_hsv = color.rgb2hsv(lena)
     """
-
-    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")
+    arr = _prepare_colorarray(rgb)
     out = np.empty_like(arr)
 
     # -- V channel
@@ -130,15 +134,7 @@ def hsv2rgb(hsv):
     >>> lena_hsv = rgb2hsv(lena)
     >>> lena_rgb = hsv2rgb(lena_hsv)
     """
-
-    if type(hsv) != np.ndarray:
-        raise TypeError, "the input array 'hsv' must be a numpy.ndarray"
-
-    if hsv.ndim != 3 or hsv.shape[2] != 3:
-        msg = "the input array 'hsv' must be have a shape == (.,.,3))"
-        raise ValueError, msg
-
-    arr = hsv.astype("float32")
+    arr = _prepare_colorarray(hsv)
 
     hi = np.floor(arr[:,:,0] * 6)
     f = arr[:,:,0] * 6 - hi

From 1a4ae96024aed2826e13cbf712397f3b32233bf5 Mon Sep 17 00:00:00 2001
From: Ralf Gommers <rgommers@Ralf-Gommerss-iMac.local>
Date: Mon, 19 Oct 2009 18:57:31 +0200
Subject: [PATCH 06/16] Add RGB to XYZ bidi conversion.

---
 scikits/image/color/colorconv.py            | 76 ++++++++++++++++++++-
 scikits/image/color/tests/test_colorconv.py | 50 +++++++++++++-
 2 files changed, 121 insertions(+), 5 deletions(-)

diff --git a/scikits/image/color/colorconv.py b/scikits/image/color/colorconv.py
index 4016c65b..28444898 100644
--- a/scikits/image/color/colorconv.py
+++ b/scikits/image/color/colorconv.py
@@ -1,17 +1,31 @@
 #!/usr/bin/env python
 # -*- coding: utf-8 -*-
 
-"""
-:author: Nicolas Pinto, 2009
+"""Functions for converting between color spaces.
+
+Supported color spaces
+----------------------
+- RGB
+- HSV
+- XYZ
+
+Authors
+-------
+- rgb2hsv was written by Nicolas Pinto
+- hsv2rgb was written by Ralf Gommers
+- other functions were originally written by Travis Oliphant and adapted by
+  Ralf Gommers
+
 :license: modified BSD
 """
 
 from __future__ import division
 
-__all__ = ['rgb2hsv', 'hsv2rgb']
+__all__ = ['rgb2hsv', 'hsv2rgb', 'rgb2xyz', 'xyz2rgb']
 __docformat__ = "restructuredtext en"
 
 import numpy as np
+from scipy import linalg
 
 
 def _prepare_colorarray(arr, dtype="float32"):
@@ -155,3 +169,59 @@ def hsv2rgb(hsv):
     out[np.isnan(out)] = 0
 
     return out
+
+
+#---------------------------------------------------------------
+# Primaries for the coordinate systems
+#---------------------------------------------------------------
+cie_primaries = [700, 546.1, 435.8]
+sb_primaries = [1./155 * 1e5, 1./190 * 1e5, 1./225 * 1e5]
+
+#---------------------------------------------------------------
+# Matrices that define conversion between different color spaces
+#---------------------------------------------------------------
+
+# From sRGB specification
+xyz_from_rgb =  [[0.412453, 0.357580, 0.180423],
+                 [0.212671, 0.715160, 0.072169],
+                 [0.019334, 0.119193, 0.950227]]
+
+rgb_from_xyz = linalg.inv(xyz_from_rgb)
+
+#-------------------------------------------------------------
+# The conversion functions that make use of the matrices above
+#-------------------------------------------------------------
+
+def _convert(matrix, arr):
+    """Do the color space conversion.
+
+    Parameters
+    ----------
+    matrix : array_like
+        The 3x3 matrix to use.
+    arr : ndarray
+        The input array.
+
+    Returns
+    -------
+    out : ndarray
+        The converted array.
+    """
+    arr = _prepare_colorarray(arr)
+    arr = np.swapaxes(arr, 0, 2)
+    oldshape = arr.shape
+    arr = np.reshape(arr, (3, -1))
+    out = np.dot(matrix, arr)
+    out.shape = oldshape
+    out = np.swapaxes(out, 2, 0)
+
+    return out
+
+
+def xyz2rgb(xyz):
+    return _convert(rgb_from_xyz, xyz)
+
+def rgb2xyz(rgb):
+    return _convert(xyz_from_rgb, rgb)
+
+
diff --git a/scikits/image/color/tests/test_colorconv.py b/scikits/image/color/tests/test_colorconv.py
index 67f641bb..ff36f2f0 100644
--- a/scikits/image/color/tests/test_colorconv.py
+++ b/scikits/image/color/tests/test_colorconv.py
@@ -1,8 +1,13 @@
 #!/usr/bin/env python
 # -*- coding: utf-8 -*-
 
-"""
-:author: Nicolas Pinto, 2009
+"""Tests for color conversion functions.
+
+Authors
+-------
+- the rgb2hsv test was written by Nicolas Pinto, 2009
+- other tests written by Ralf Gommers, 2009
+
 :license: modified BSD
 """
 
@@ -15,6 +20,8 @@ from scikits.image.io import imread
 from scikits.image.color import (
     rgb2hsv,
     hsv2rgb,
+    rgb2xyz,
+    xyz2rgb
     )
 
 from scikits.image import data_dir
@@ -27,6 +34,13 @@ class TestColorconv(TestCase):
     img_rgb = imread(os.path.join(data_dir, 'color.png'))
     img_grayscale = imread(os.path.join(data_dir, 'camera.png'))
 
+    colbars = np.array([[1, 1, 0, 0, 1, 1, 0, 0],
+                        [1, 1, 1, 1, 0, 0, 0, 0],
+                        [1, 0, 1, 0, 1, 0, 1, 0]])
+    colbars_array = np.swapaxes(colbars.reshape(3, 4, 2), 0, 2)
+    colbars_point75 = colbars * 0.75
+    colbars_point75_array = np.swapaxes(colbars_point75.reshape(3, 4, 2), 0, 2)
+
     # RGB to HSV
     def test_rgb2hsv_conversion(self):
         rgb = self.img_rgb.astype("float32")[::16, ::16]
@@ -67,6 +81,38 @@ class TestColorconv(TestCase):
         self.assertRaises(TypeError, hsv2rgb, [self.img_rgb[0,0]])
 
 
+    # RGB to XYZ
+    def test_rgb2xyz_conversion(self):
+        gt = np.array([[[ 0.950456,  1.      ,  1.088754],
+                        [ 0.538003,  0.787329,  1.06942 ],
+                        [ 0.592876,  0.28484 ,  0.969561],
+                        [ 0.180423,  0.072169,  0.950227]],
+                       [[ 0.770033,  0.927831,  0.138527],
+                        [ 0.35758 ,  0.71516 ,  0.119193],
+                        [ 0.412453,  0.212671,  0.019334],
+                        [ 0.      ,  0.      ,  0.      ]]])
+
+        assert_almost_equal(rgb2xyz(self.colbars_array), gt)
+
+    # stop repeating the "raises" checks for all other functions that are
+    # implemented with color._convert()
+    def test_rgb2xyz_error_grayscale(self):
+        self.assertRaises(ValueError, rgb2xyz, self.img_grayscale)
+
+    def test_rgb2xyz_error_one_element(self):
+        self.assertRaises(ValueError, rgb2xyz, self.img_rgb[0,0])
+
+    def test_rgb2xyz_error_list(self):
+        self.assertRaises(TypeError, rgb2xyz, [self.img_rgb[0,0]])
+
+
+    # XYZ to RGB
+    def test_xyz2rgb_conversion(self):
+        # only roundtrip test, we checked rgb2xyz above already
+        assert_almost_equal(xyz2rgb(rgb2xyz(self.colbars_array)),
+                            self.colbars_array)
+
+
 if __name__ == "__main__":
     run_module_suite()
 

From 5de50145897a49fc36edd377ea1cfab34b4cc6a7 Mon Sep 17 00:00:00 2001
From: Ralf Gommers <rgommers@Ralf-Gommerss-iMac.local>
Date: Mon, 19 Oct 2009 19:39:00 +0200
Subject: [PATCH 07/16] Add docstrings for rgb2xyz and xyz2rgb.

---
 scikits/image/color/colorconv.py | 71 ++++++++++++++++++++++++++++++++
 1 file changed, 71 insertions(+)

diff --git a/scikits/image/color/colorconv.py b/scikits/image/color/colorconv.py
index 28444898..f6f485b3 100644
--- a/scikits/image/color/colorconv.py
+++ b/scikits/image/color/colorconv.py
@@ -219,9 +219,80 @@ def _convert(matrix, arr):
 
 
 def xyz2rgb(xyz):
+    """XYZ to RGB color space conversion.
+
+    Parameters
+    ----------
+    xyz : ndarray
+        The image in XYZ format, in a 3-D array of shape (.., .., 3).
+
+    Returns
+    -------
+    out : ndarray
+        The image in RGB format, in a 3-D array of shape (.., .., 3).
+
+    Raises
+    ------
+    ValueError
+        If `xyz` is not a 3-D array of shape (.., .., 3).
+
+    Notes
+    -----
+    The CIE XYZ color space is derived from the CIE RGB color space. Note
+    however that this function converts to sRGB.
+
+    References
+    ----------
+    .. [1] http://en.wikipedia.org/wiki/CIE_1931_color_space
+
+    Examples
+    --------
+    >>> import os
+    >>> from scikits.image import data_dir
+    >>> from scikits.image.io import imread
+
+    >>> lena = imread(os.path.join(data_dir, 'lena.png'))
+    >>> lena_xyz = rgb2xyz(lena)
+    >>> lena_rgb = xyz2rgb(lena_hsv)
+    """
     return _convert(rgb_from_xyz, xyz)
 
 def rgb2xyz(rgb):
+    """RGB to XYZ color space conversion.
+
+    Parameters
+    ----------
+    rgb : ndarray
+        The image in RGB format, in a 3-D array of shape (.., .., 3).
+
+    Returns
+    -------
+    out : ndarray
+        The image in XYZ format, in a 3-D array of shape (.., .., 3).
+
+    Raises
+    ------
+    ValueError
+        If `rgb` is not a 3-D array of shape (.., .., 3).
+
+    Notes
+    -----
+    The CIE XYZ color space is derived from the CIE RGB color space. Note
+    however that this function converts from sRGB.
+
+    References
+    ----------
+    .. [1] http://en.wikipedia.org/wiki/CIE_1931_color_space
+
+    Examples
+    --------
+    >>> import os
+    >>> from scikits.image import data_dir
+    >>> from scikits.image.io import imread
+
+    >>> lena = imread(os.path.join(data_dir, 'lena.png'))
+    >>> lena_xyz = rgb2xyz(lena)
+    """
     return _convert(xyz_from_rgb, rgb)
 
 

From 94f5eeac25c8c96380d56e25b44c0b283d9589d9 Mon Sep 17 00:00:00 2001
From: Ralf Gommers <rgommers@Ralf-Gommerss-iMac.local>
Date: Tue, 20 Oct 2009 12:10:33 +0200
Subject: [PATCH 08/16] Add description of the API to the module docstring.

This is not all implemented yet, mostly a description of what I want it to look
like in the end. This required figuring out the right matrices based on some of
the random ones in Travis' code. Should not be too difficult.
---
 scikits/image/color/colorconv.py | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/scikits/image/color/colorconv.py b/scikits/image/color/colorconv.py
index f6f485b3..39337b12 100644
--- a/scikits/image/color/colorconv.py
+++ b/scikits/image/color/colorconv.py
@@ -3,6 +3,15 @@
 
 """Functions for converting between color spaces.
 
+The "central" color space in this module is RGB, more specifically the linear
+sRGB color space using D65 as a white-point (IEC 61966-2-1).  This represents a
+standard monitor (w/o gamma correction).
+
+The API consists of functions to convert to and from RGB as defined above, as
+well as a generic function to convert to and from any supported color space
+(which is done through RGB in most cases).
+
+
 Supported color spaces
 ----------------------
 - RGB
@@ -188,6 +197,14 @@ xyz_from_rgb =  [[0.412453, 0.357580, 0.180423],
 
 rgb_from_xyz = linalg.inv(xyz_from_rgb)
 
+# Matrices from Jain. TODO: find complete reference.
+xyz_from_rgbcie = [[0.490, 0.310, 0.200],
+                   [0.177, 0.813, 0.011],
+                   [0.000, 0.010, 0.990]]
+
+rgbcie_from_xyz = linalg.inv(xyz_from_rgbcie)
+
+
 #-------------------------------------------------------------
 # The conversion functions that make use of the matrices above
 #-------------------------------------------------------------

From cf379160224e155dd1ddc0ae23a1c862df8a4e32 Mon Sep 17 00:00:00 2001
From: Ralf Gommers <rgommers@Ralf-Gommerss-iMac.local>
Date: Tue, 20 Oct 2009 13:12:18 +0200
Subject: [PATCH 09/16] Convert matrix lists to arrays, add RGB CIE color
 space.

---
 scikits/image/color/colorconv.py | 89 ++++++++++++++++++++++++++++----
 1 file changed, 80 insertions(+), 9 deletions(-)

diff --git a/scikits/image/color/colorconv.py b/scikits/image/color/colorconv.py
index 39337b12..4b3ed5f4 100644
--- a/scikits/image/color/colorconv.py
+++ b/scikits/image/color/colorconv.py
@@ -16,6 +16,7 @@ Supported color spaces
 ----------------------
 - RGB
 - HSV
+- RGB CIE
 - XYZ
 
 Authors
@@ -183,27 +184,31 @@ def hsv2rgb(hsv):
 #---------------------------------------------------------------
 # Primaries for the coordinate systems
 #---------------------------------------------------------------
-cie_primaries = [700, 546.1, 435.8]
-sb_primaries = [1./155 * 1e5, 1./190 * 1e5, 1./225 * 1e5]
+cie_primaries = np.array([700, 546.1, 435.8])
+sb_primaries = np.array([1./155, 1./190, 1./225]) * 1e5
 
 #---------------------------------------------------------------
 # Matrices that define conversion between different color spaces
 #---------------------------------------------------------------
 
 # From sRGB specification
-xyz_from_rgb =  [[0.412453, 0.357580, 0.180423],
-                 [0.212671, 0.715160, 0.072169],
-                 [0.019334, 0.119193, 0.950227]]
+xyz_from_rgb =  np.array([[0.412453, 0.357580, 0.180423],
+                          [0.212671, 0.715160, 0.072169],
+                          [0.019334, 0.119193, 0.950227]])
 
 rgb_from_xyz = linalg.inv(xyz_from_rgb)
 
-# Matrices from Jain. TODO: find complete reference.
-xyz_from_rgbcie = [[0.490, 0.310, 0.200],
-                   [0.177, 0.813, 0.011],
-                   [0.000, 0.010, 0.990]]
+# From http://en.wikipedia.org/wiki/CIE_1931_color_space
+# Note: Travis' code did not have the divide by 0.17697
+xyz_from_rgbcie = np.array([[0.49, 0.31, 0.20],
+                            [0.17697, 0.81240, 0.01063],
+                            [0.00, 0.01, 0.99]]) / 0.17697
 
 rgbcie_from_xyz = linalg.inv(xyz_from_rgbcie)
 
+# construct matrices to and from rgb:
+rgbcie_from_rgb = np.dot(rgbcie_from_xyz, xyz_from_rgb)
+rgb_from_rgbcie = np.dot(rgb_from_xyz, xyz_from_rgb)
 
 #-------------------------------------------------------------
 # The conversion functions that make use of the matrices above
@@ -312,4 +317,70 @@ def rgb2xyz(rgb):
     """
     return _convert(xyz_from_rgb, rgb)
 
+def rgb2rgbcie(rgb):
+    """RGB to RGB CIE color space conversion.
+
+    Parameters
+    ----------
+    rgb : ndarray
+        The image in RGB format, in a 3-D array of shape (.., .., 3).
+
+    Returns
+    -------
+    out : ndarray
+        The image in RGB CIE format, in a 3-D array of shape (.., .., 3).
+
+    Raises
+    ------
+    ValueError
+        If `rgb` is not a 3-D array of shape (.., .., 3).
+
+    References
+    ----------
+    .. [1] http://en.wikipedia.org/wiki/CIE_1931_color_space
+
+    Examples
+    --------
+    >>> import os
+    >>> from scikits.image import data_dir
+    >>> from scikits.image.io import imread
+
+    >>> lena = imread(os.path.join(data_dir, 'lena.png'))
+    >>> lena_rgbcie = rgb2rgbcie(lena)
+    """
+    return _convert(rgbcie_from_rgb, rgb)
+
+def rgbcie2rgb(rgbcie):
+    """RGB CIE to RGB color space conversion.
+
+    Parameters
+    ----------
+    rgbcie : ndarray
+        The image in RGB CIE format, in a 3-D array of shape (.., .., 3).
+
+    Returns
+    -------
+    out : ndarray
+        The image in RGB format, in a 3-D array of shape (.., .., 3).
+
+    Raises
+    ------
+    ValueError
+        If `rgbcie` is not a 3-D array of shape (.., .., 3).
+
+    References
+    ----------
+    .. [1] http://en.wikipedia.org/wiki/CIE_1931_color_space
+
+    Examples
+    --------
+    >>> import os
+    >>> from scikits.image import data_dir
+    >>> from scikits.image.io import imread
+
+    >>> lena = imread(os.path.join(data_dir, 'lena.png'))
+    >>> lena_rgbcie = rgb2rgbcie(lena)
+    >>> lena_rgb = rgbcie2rgb(lena_hsv)
+    """
+    return _convert(rgb_from_rgbcie, rgbcie)
 

From 57b73a5f5346115e116f810144188472d97aff58 Mon Sep 17 00:00:00 2001
From: Ralf Gommers <rgommers@Ralf-Gommerss-iMac.local>
Date: Wed, 21 Oct 2009 18:10:31 +0200
Subject: [PATCH 10/16] Add NTSC color space.

Also a typo in rgbcie fixed.
---
 scikits/image/color/colorconv.py            | 85 ++++++++++++++++++++-
 scikits/image/color/tests/test_colorconv.py | 51 +++++++++++--
 2 files changed, 129 insertions(+), 7 deletions(-)

diff --git a/scikits/image/color/colorconv.py b/scikits/image/color/colorconv.py
index 4b3ed5f4..e431e083 100644
--- a/scikits/image/color/colorconv.py
+++ b/scikits/image/color/colorconv.py
@@ -18,6 +18,7 @@ Supported color spaces
 - HSV
 - RGB CIE
 - XYZ
+- NTSC
 
 Authors
 -------
@@ -31,7 +32,8 @@ Authors
 
 from __future__ import division
 
-__all__ = ['rgb2hsv', 'hsv2rgb', 'rgb2xyz', 'xyz2rgb']
+__all__ = ['rgb2hsv', 'hsv2rgb', 'rgb2xyz', 'xyz2rgb', 'rgb2rgbcie', 'rgbcie2rgb',
+           'rgb2ntsc', 'ntsc2rgb']
 __docformat__ = "restructuredtext en"
 
 import numpy as np
@@ -208,7 +210,19 @@ rgbcie_from_xyz = linalg.inv(xyz_from_rgbcie)
 
 # construct matrices to and from rgb:
 rgbcie_from_rgb = np.dot(rgbcie_from_xyz, xyz_from_rgb)
-rgb_from_rgbcie = np.dot(rgb_from_xyz, xyz_from_rgb)
+rgb_from_rgbcie = np.dot(rgb_from_xyz, xyz_from_rgbcie)
+
+# from Travis' code. "Matrices from Jain". TODO: find reference.
+ntsc_from_xyz = np.array([[1.910, -0.533, -0.288],
+                          [-0.985, 2.000, -0.028],
+                          [0.058, -0.118, 0.896]])
+
+xyz_from_ntsc = linalg.inv(ntsc_from_xyz)
+
+# construct matrices to and from rgb:
+ntsc_from_rgb = np.dot(ntsc_from_xyz, xyz_from_rgb)
+rgb_from_ntsc = np.dot(rgb_from_xyz, xyz_from_ntsc)
+
 
 #-------------------------------------------------------------
 # The conversion functions that make use of the matrices above
@@ -384,3 +398,70 @@ def rgbcie2rgb(rgbcie):
     """
     return _convert(rgb_from_rgbcie, rgbcie)
 
+def rgb2ntsc(rgb):
+    """RGB to NTSC color space conversion.
+
+    Parameters
+    ----------
+    rgb : ndarray
+        The image in RGB format, in a 3-D array of shape (.., .., 3).
+
+    Returns
+    -------
+    out : ndarray
+        The image in NTSC format, in a 3-D array of shape (.., .., 3).
+
+    Raises
+    ------
+    ValueError
+        If `rgb` is not a 3-D array of shape (.., .., 3).
+
+    References
+    ----------
+    .. [1] http://en.wikipedia.org/wiki/NTSC
+
+    Examples
+    --------
+    >>> import os
+    >>> from scikits.image import data_dir
+    >>> from scikits.image.io import imread
+
+    >>> lena = imread(os.path.join(data_dir, 'lena.png'))
+    >>> lena_ntsc = rgb2ntsc(lena)
+    """
+    return _convert(ntsc_from_rgb, rgb)
+
+def ntsc2rgb(ntsc):
+    """NTSC to RGB color space conversion.
+
+    Parameters
+    ----------
+    ntsc : ndarray
+        The image in NTSC format, in a 3-D array of shape (.., .., 3).
+
+    Returns
+    -------
+    out : ndarray
+        The image in RGB format, in a 3-D array of shape (.., .., 3).
+
+    Raises
+    ------
+    ValueError
+        If `ntsc` is not a 3-D array of shape (.., .., 3).
+
+    References
+    ----------
+    .. [1] http://en.wikipedia.org/wiki/NTSC
+
+    Examples
+    --------
+    >>> import os
+    >>> from scikits.image import data_dir
+    >>> from scikits.image.io import imread
+
+    >>> lena = imread(os.path.join(data_dir, 'lena.png'))
+    >>> lena_ntsc = rgb2ntsc(lena)
+    >>> lena_rgb = ntsc2rgb(lena_hsv)
+    """
+    return _convert(rgb_from_ntsc, ntsc)
+
diff --git a/scikits/image/color/tests/test_colorconv.py b/scikits/image/color/tests/test_colorconv.py
index ff36f2f0..842e1acc 100644
--- a/scikits/image/color/tests/test_colorconv.py
+++ b/scikits/image/color/tests/test_colorconv.py
@@ -18,10 +18,10 @@ from numpy.testing import *
 
 from scikits.image.io import imread
 from scikits.image.color import (
-    rgb2hsv,
-    hsv2rgb,
-    rgb2xyz,
-    xyz2rgb
+    rgb2hsv, hsv2rgb,
+    rgb2xyz, xyz2rgb,
+    rgb2rgbcie, rgbcie2rgb,
+    rgb2ntsc, ntsc2rgb
     )
 
 from scikits.image import data_dir
@@ -91,7 +91,6 @@ class TestColorconv(TestCase):
                         [ 0.35758 ,  0.71516 ,  0.119193],
                         [ 0.412453,  0.212671,  0.019334],
                         [ 0.      ,  0.      ,  0.      ]]])
-
         assert_almost_equal(rgb2xyz(self.colbars_array), gt)
 
     # stop repeating the "raises" checks for all other functions that are
@@ -113,6 +112,48 @@ class TestColorconv(TestCase):
                             self.colbars_array)
 
 
+    # RGB to RGB CIE
+    def test_rgb2rgbcie_conversion(self):
+        gt = np.array([[[ 0.1488856 ,  0.18288098,  0.19277574],
+                        [ 0.01163224,  0.16649536,  0.18948516],
+                        [ 0.12259182,  0.03308008,  0.17298223],
+                        [-0.01466154,  0.01669446,  0.16969164]],
+                       [[ 0.16354714,  0.16618652,  0.0230841 ],
+                        [ 0.02629378,  0.1498009 ,  0.01979351],
+                        [ 0.13725336,  0.01638562,  0.00329059],
+                        [ 0.        ,  0.        ,  0.        ]]])
+        assert_almost_equal(rgb2rgbcie(self.colbars_array), gt)
+
+
+    # RGB CIE to RGB
+    def test_rgbcie2rgb_conversion(self):
+        # only roundtrip test, we checked rgb2rgbcie above already
+        assert_almost_equal(rgbcie2rgb(rgb2rgbcie(self.colbars_array)),
+                            self.colbars_array)
+
+
+    # RGB to NTSC
+    def test_rgb2ntsc_conversion(self):
+        gt = np.array([[[ 0.96880981,  1.03331573,  0.91265003],
+                        [ 0.29994641,  1.01478128,  0.89649967],
+                        [ 0.70133987, -0.04145057,  0.86950234],
+                        [ 0.03247648, -0.05998501,  0.85335198]],
+                       [[ 0.93633333,  1.09330074,  0.05929805],
+                        [ 0.26746994,  1.0747663 ,  0.04314769],
+                        [ 0.66886339,  0.01853444,  0.01615036],
+                        [ 0.        ,  0.        ,  0.        ]]])
+        assert_almost_equal(rgb2ntsc(self.colbars_array), gt)
+
+
+    # NTSC to RGB
+    def test_ntsc2rgb_conversion(self):
+        # only roundtrip test, we checked rgb2ntsc above already
+        assert_almost_equal(ntsc2rgb(rgb2ntsc(self.colbars_array)),
+                            self.colbars_array)
+
+
+
+
 if __name__ == "__main__":
     run_module_suite()
 

From 64f65e01607c3e26011843b3713945759a9a9812 Mon Sep 17 00:00:00 2001
From: Ralf Gommers <rgommers@Ralf-Gommerss-iMac.local>
Date: Thu, 22 Oct 2009 01:14:02 +0200
Subject: [PATCH 11/16] Clean up the colorconv module docstring.

---
 scikits/image/color/colorconv.py | 38 +++++++++++++++++++++-----------
 1 file changed, 25 insertions(+), 13 deletions(-)

diff --git a/scikits/image/color/colorconv.py b/scikits/image/color/colorconv.py
index e431e083..aa757ddd 100644
--- a/scikits/image/color/colorconv.py
+++ b/scikits/image/color/colorconv.py
@@ -4,8 +4,9 @@
 """Functions for converting between color spaces.
 
 The "central" color space in this module is RGB, more specifically the linear
-sRGB color space using D65 as a white-point (IEC 61966-2-1).  This represents a
-standard monitor (w/o gamma correction).
+sRGB color space using D65 as a white-point [1]_.  This represents a
+standard monitor (w/o gamma correction). For a good FAQ on color spaces see
+[2]_.
 
 The API consists of functions to convert to and from RGB as defined above, as
 well as a generic function to convert to and from any supported color space
@@ -14,20 +15,31 @@ well as a generic function to convert to and from any supported color space
 
 Supported color spaces
 ----------------------
-- RGB
-- HSV
-- RGB CIE
-- XYZ
-- NTSC
+* RGB : Red Green Blue.
+        Here the sRGB standard [1]_.
+* HSV : Hue, Saturation, Value.
+        Uniquely defined when related to sRGB [3]_.
+* RGB CIE : Red Green Blue.
+        The original RGB CIE standard from 1931 [4]_. Primary colors are 700 nm
+        (red), 546.1 nm (blue) and 435.8 nm (green).
+* XYZ CIE : XYZ
+        Derived from the RGB CIE color space. Chosen such that
+        ``x == y == z == 1/3`` at the whitepoint, and all color matching
+        functions are greater than zero everywhere.
+* NTSC
 
-Authors
--------
-- rgb2hsv was written by Nicolas Pinto
-- hsv2rgb was written by Ralf Gommers
-- other functions were originally written by Travis Oliphant and adapted by
-  Ralf Gommers
+:author: Nicolas Pinto (rgb2hsv)
+:author: Ralf Gommers (hsv2rgb)
+:author: Travis Oliphant (XYZ and RGB CIE functions)
 
 :license: modified BSD
+
+References
+----------
+.. [1] Official specification of sRGB, IEC 61966-2-1:1999.
+.. [2] http://www.poynton.com/ColorFAQ.html
+.. [3] http://en.wikipedia.org/wiki/HSL_and_HSV
+.. [4] http://en.wikipedia.org/wiki/CIE_1931_color_space
 """
 
 from __future__ import division

From d7b49ef950065c22c5d07c78e07da670a4d65525 Mon Sep 17 00:00:00 2001
From: Ralf Gommers <rgommers@Ralf-Gommerss-iMac.local>
Date: Thu, 22 Oct 2009 01:18:02 +0200
Subject: [PATCH 12/16] Remove NTSC color space.

Reason: it was not clear exactly what this was and what it was for. The color
space used for NTSC video is YIQ, not RGB NTSC.
---
 scikits/image/color/colorconv.py            | 85 +--------------------
 scikits/image/color/tests/test_colorconv.py | 25 +-----
 2 files changed, 4 insertions(+), 106 deletions(-)

diff --git a/scikits/image/color/colorconv.py b/scikits/image/color/colorconv.py
index aa757ddd..effb7dc6 100644
--- a/scikits/image/color/colorconv.py
+++ b/scikits/image/color/colorconv.py
@@ -26,7 +26,6 @@ Supported color spaces
         Derived from the RGB CIE color space. Chosen such that
         ``x == y == z == 1/3`` at the whitepoint, and all color matching
         functions are greater than zero everywhere.
-* NTSC
 
 :author: Nicolas Pinto (rgb2hsv)
 :author: Ralf Gommers (hsv2rgb)
@@ -44,8 +43,9 @@ References
 
 from __future__ import division
 
-__all__ = ['rgb2hsv', 'hsv2rgb', 'rgb2xyz', 'xyz2rgb', 'rgb2rgbcie', 'rgbcie2rgb',
-           'rgb2ntsc', 'ntsc2rgb']
+__all__ = ['rgb2hsv', 'hsv2rgb', 'rgb2xyz', 'xyz2rgb', 'rgb2rgbcie',
+           'rgbcie2rgb']
+
 __docformat__ = "restructuredtext en"
 
 import numpy as np
@@ -224,17 +224,6 @@ rgbcie_from_xyz = linalg.inv(xyz_from_rgbcie)
 rgbcie_from_rgb = np.dot(rgbcie_from_xyz, xyz_from_rgb)
 rgb_from_rgbcie = np.dot(rgb_from_xyz, xyz_from_rgbcie)
 
-# from Travis' code. "Matrices from Jain". TODO: find reference.
-ntsc_from_xyz = np.array([[1.910, -0.533, -0.288],
-                          [-0.985, 2.000, -0.028],
-                          [0.058, -0.118, 0.896]])
-
-xyz_from_ntsc = linalg.inv(ntsc_from_xyz)
-
-# construct matrices to and from rgb:
-ntsc_from_rgb = np.dot(ntsc_from_xyz, xyz_from_rgb)
-rgb_from_ntsc = np.dot(rgb_from_xyz, xyz_from_ntsc)
-
 
 #-------------------------------------------------------------
 # The conversion functions that make use of the matrices above
@@ -409,71 +398,3 @@ def rgbcie2rgb(rgbcie):
     >>> lena_rgb = rgbcie2rgb(lena_hsv)
     """
     return _convert(rgb_from_rgbcie, rgbcie)
-
-def rgb2ntsc(rgb):
-    """RGB to NTSC color space conversion.
-
-    Parameters
-    ----------
-    rgb : ndarray
-        The image in RGB format, in a 3-D array of shape (.., .., 3).
-
-    Returns
-    -------
-    out : ndarray
-        The image in NTSC format, in a 3-D array of shape (.., .., 3).
-
-    Raises
-    ------
-    ValueError
-        If `rgb` is not a 3-D array of shape (.., .., 3).
-
-    References
-    ----------
-    .. [1] http://en.wikipedia.org/wiki/NTSC
-
-    Examples
-    --------
-    >>> import os
-    >>> from scikits.image import data_dir
-    >>> from scikits.image.io import imread
-
-    >>> lena = imread(os.path.join(data_dir, 'lena.png'))
-    >>> lena_ntsc = rgb2ntsc(lena)
-    """
-    return _convert(ntsc_from_rgb, rgb)
-
-def ntsc2rgb(ntsc):
-    """NTSC to RGB color space conversion.
-
-    Parameters
-    ----------
-    ntsc : ndarray
-        The image in NTSC format, in a 3-D array of shape (.., .., 3).
-
-    Returns
-    -------
-    out : ndarray
-        The image in RGB format, in a 3-D array of shape (.., .., 3).
-
-    Raises
-    ------
-    ValueError
-        If `ntsc` is not a 3-D array of shape (.., .., 3).
-
-    References
-    ----------
-    .. [1] http://en.wikipedia.org/wiki/NTSC
-
-    Examples
-    --------
-    >>> import os
-    >>> from scikits.image import data_dir
-    >>> from scikits.image.io import imread
-
-    >>> lena = imread(os.path.join(data_dir, 'lena.png'))
-    >>> lena_ntsc = rgb2ntsc(lena)
-    >>> lena_rgb = ntsc2rgb(lena_hsv)
-    """
-    return _convert(rgb_from_ntsc, ntsc)
-
diff --git a/scikits/image/color/tests/test_colorconv.py b/scikits/image/color/tests/test_colorconv.py
index 842e1acc..5fcfe053 100644
--- a/scikits/image/color/tests/test_colorconv.py
+++ b/scikits/image/color/tests/test_colorconv.py
@@ -20,8 +20,7 @@ from scikits.image.io import imread
 from scikits.image.color import (
     rgb2hsv, hsv2rgb,
     rgb2xyz, xyz2rgb,
-    rgb2rgbcie, rgbcie2rgb,
-    rgb2ntsc, ntsc2rgb
+    rgb2rgbcie, rgbcie2rgb
     )
 
 from scikits.image import data_dir
@@ -132,28 +131,6 @@ class TestColorconv(TestCase):
                             self.colbars_array)
 
 
-    # RGB to NTSC
-    def test_rgb2ntsc_conversion(self):
-        gt = np.array([[[ 0.96880981,  1.03331573,  0.91265003],
-                        [ 0.29994641,  1.01478128,  0.89649967],
-                        [ 0.70133987, -0.04145057,  0.86950234],
-                        [ 0.03247648, -0.05998501,  0.85335198]],
-                       [[ 0.93633333,  1.09330074,  0.05929805],
-                        [ 0.26746994,  1.0747663 ,  0.04314769],
-                        [ 0.66886339,  0.01853444,  0.01615036],
-                        [ 0.        ,  0.        ,  0.        ]]])
-        assert_almost_equal(rgb2ntsc(self.colbars_array), gt)
-
-
-    # NTSC to RGB
-    def test_ntsc2rgb_conversion(self):
-        # only roundtrip test, we checked rgb2ntsc above already
-        assert_almost_equal(ntsc2rgb(rgb2ntsc(self.colbars_array)),
-                            self.colbars_array)
-
-
-
-
 if __name__ == "__main__":
     run_module_suite()
 

From caede7762b9a7a23ac80d051dfed3871c93a1de4 Mon Sep 17 00:00:00 2001
From: Ralf Gommers <rgommers@Ralf-Gommerss-iMac.local>
Date: Thu, 22 Oct 2009 11:45:57 +0200
Subject: [PATCH 13/16] Add a function to convert from any color space directly
 to any other space.

---
 scikits/image/color/colorconv.py            | 54 ++++++++++++++++++++-
 scikits/image/color/tests/test_colorconv.py | 22 ++++++++-
 2 files changed, 73 insertions(+), 3 deletions(-)

diff --git a/scikits/image/color/colorconv.py b/scikits/image/color/colorconv.py
index effb7dc6..8fccf6ba 100644
--- a/scikits/image/color/colorconv.py
+++ b/scikits/image/color/colorconv.py
@@ -43,8 +43,8 @@ References
 
 from __future__ import division
 
-__all__ = ['rgb2hsv', 'hsv2rgb', 'rgb2xyz', 'xyz2rgb', 'rgb2rgbcie',
-           'rgbcie2rgb']
+__all__ = ['convert_colorspace', 'rgb2hsv', 'hsv2rgb', 'rgb2xyz', 'xyz2rgb',
+           'rgb2rgbcie', 'rgbcie2rgb']
 
 __docformat__ = "restructuredtext en"
 
@@ -52,6 +52,56 @@ import numpy as np
 from scipy import linalg
 
 
+def convert_colorspace(arr, fromspace, tospace):
+    """Convert an image array to a new color space.
+
+    Parameters
+    ----------
+    arr : ndarray
+        The image to convert.
+    fromspace : str
+        The color space to convert from. Valid color space strings are
+        ['RGB', 'HSV', 'RGB CIE', 'XYZ']. Value may also be specified as lower
+        case.
+    tospace : str
+        The color space to convert to. Valid color space strings are
+        ['RGB', 'HSV', 'RGB CIE', 'XYZ']. Value may also be specified as lower
+        case.
+
+    Returns
+    -------
+    newarr : ndarray
+        The converted image.
+
+    Notes
+    -----
+    Conversion occurs through the "central" RGB color space, i.e. conversion
+    from XYZ to HSV is implemented as XYZ -> RGB -> HSV instead of directly.
+
+    Examples
+    --------
+    >>> import os
+    >>> from scikits.image import data_dir
+    >>> from scikits.image.io import imread
+
+    >>> lena = imread(os.path.join(data_dir, 'lena.png'))
+    >>> lena_hsv = convert_colorspace(lena, 'RGB', 'HSV')
+    """
+    fromdict = {'RGB':lambda im: im, 'HSV':hsv2rgb, 'RGB CIE':rgbcie2rgb,
+                'XYZ':xyz2rgb}
+    todict = {'RGB':lambda im:im, 'HSV':rgb2hsv, 'RGB CIE':rgb2rgbcie,
+              'XYZ':rgb2xyz}
+
+    fromspace = fromspace.upper()
+    tospace = tospace.upper()
+    if not fromspace in fromdict.keys():
+        raise ValueError, 'fromspace needs to be one of %s'%fromdict.keys()
+    if not tospace in todict.keys():
+        raise ValueError, 'tospace needs to be one of %s'%todict.keys()
+
+    return todict[tospace](fromdict[fromspace](arr))
+
+
 def _prepare_colorarray(arr, dtype="float32"):
     """Check the shape of the array, and give it the requested type"""
     if type(arr) != np.ndarray:
diff --git a/scikits/image/color/tests/test_colorconv.py b/scikits/image/color/tests/test_colorconv.py
index 5fcfe053..9473b456 100644
--- a/scikits/image/color/tests/test_colorconv.py
+++ b/scikits/image/color/tests/test_colorconv.py
@@ -20,7 +20,8 @@ from scikits.image.io import imread
 from scikits.image.color import (
     rgb2hsv, hsv2rgb,
     rgb2xyz, xyz2rgb,
-    rgb2rgbcie, rgbcie2rgb
+    rgb2rgbcie, rgbcie2rgb,
+    convert_colorspace
     )
 
 from scikits.image import data_dir
@@ -130,6 +131,25 @@ class TestColorconv(TestCase):
         assert_almost_equal(rgbcie2rgb(rgb2rgbcie(self.colbars_array)),
                             self.colbars_array)
 
+    def test_convert_colorspace(self):
+        colspaces = ['HSV', 'RGB CIE', 'XYZ']
+        colfuncs_from = [hsv2rgb, rgbcie2rgb, xyz2rgb]
+        colfuncs_to = [rgb2hsv, rgb2rgbcie, rgb2xyz]
+
+        assert_almost_equal(convert_colorspace(self.colbars_array, 'RGB',
+                                               'RGB'), self.colbars_array)
+        for i, space in enumerate(colspaces):
+            gt = colfuncs_from[i](self.colbars_array)
+            assert_almost_equal(convert_colorspace(self.colbars_array, space,
+                                                  'RGB'), gt)
+            gt = colfuncs_to[i](self.colbars_array)
+            assert_almost_equal(convert_colorspace(self.colbars_array, 'RGB',
+                                                   space), gt)
+
+        self.assertRaises(ValueError, convert_colorspace, self.colbars_array,
+                                                           'nokey', 'XYZ')
+        self.assertRaises(ValueError, convert_colorspace, self.colbars_array,
+                                                           'RGB', 'nokey')
 
 if __name__ == "__main__":
     run_module_suite()

From 91b0d6380012e0731a89a6bab7552fd97f127ed6 Mon Sep 17 00:00:00 2001
From: Ralf Gommers <rgommers@Ralf-Gommerss-iMac.local>
Date: Fri, 23 Oct 2009 10:35:27 +0200
Subject: [PATCH 14/16] Remove explicit checks of image type and NaN, and
 correct dtype descriptor.

---
 scikits/image/color/colorconv.py            | 29 +++++++++------------
 scikits/image/color/tests/test_colorconv.py |  9 -------
 2 files changed, 13 insertions(+), 25 deletions(-)

diff --git a/scikits/image/color/colorconv.py b/scikits/image/color/colorconv.py
index 8fccf6ba..d0ac2fbf 100644
--- a/scikits/image/color/colorconv.py
+++ b/scikits/image/color/colorconv.py
@@ -57,7 +57,7 @@ def convert_colorspace(arr, fromspace, tospace):
 
     Parameters
     ----------
-    arr : ndarray
+    arr : array_like
         The image to convert.
     fromspace : str
         The color space to convert from. Valid color space strings are
@@ -102,10 +102,9 @@ def convert_colorspace(arr, fromspace, tospace):
     return todict[tospace](fromdict[fromspace](arr))
 
 
-def _prepare_colorarray(arr, dtype="float32"):
-    """Check the shape of the array, and give it the requested type"""
-    if type(arr) != np.ndarray:
-        raise TypeError, "the input array must be a numpy.ndarray"
+def _prepare_colorarray(arr, dtype=np.float32):
+    """Check the shape of the array, and give it the requested type."""
+    arr = np.asanyarray(arr)
 
     if arr.ndim != 3 or arr.shape[2] != 3:
         msg = "the input array must be have a shape == (.,.,3))"
@@ -113,12 +112,13 @@ def _prepare_colorarray(arr, dtype="float32"):
 
     return arr.astype(dtype)
 
+
 def rgb2hsv(rgb):
     """RGB to HSV color space conversion.
 
     Parameters
     ----------
-    rgb : ndarray
+    rgb : array_like
         The image in RGB format, in a 3-D array of shape (.., .., 3).
 
     Returns
@@ -190,7 +190,7 @@ def hsv2rgb(hsv):
 
     Parameters
     ----------
-    hsv : ndarray
+    hsv : array_like
         The image in HSV format, in a 3-D array of shape (.., .., 3).
 
     Returns
@@ -231,7 +231,7 @@ def hsv2rgb(hsv):
     t = arr[:,:,2] * (1 - (1 - f) * arr[:,:,1])
     v = arr[:,:,2]
 
-    hi = np.dstack([hi, hi, hi]).astype("uint8") % 6
+    hi = np.dstack([hi, hi, hi]).astype(np.uint8) % 6
     out = np.choose(hi, [np.dstack((v, t, p)),
                          np.dstack((q, v, p)),
                          np.dstack((p, v, t)),
@@ -239,9 +239,6 @@ def hsv2rgb(hsv):
                          np.dstack((t, p, v)),
                          np.dstack((v, p, q))])
 
-    # remove NaN
-    out[np.isnan(out)] = 0
-
     return out
 
 
@@ -286,7 +283,7 @@ def _convert(matrix, arr):
     ----------
     matrix : array_like
         The 3x3 matrix to use.
-    arr : ndarray
+    arr : array_like
         The input array.
 
     Returns
@@ -310,7 +307,7 @@ def xyz2rgb(xyz):
 
     Parameters
     ----------
-    xyz : ndarray
+    xyz : array_like
         The image in XYZ format, in a 3-D array of shape (.., .., 3).
 
     Returns
@@ -349,7 +346,7 @@ def rgb2xyz(rgb):
 
     Parameters
     ----------
-    rgb : ndarray
+    rgb : array_like
         The image in RGB format, in a 3-D array of shape (.., .., 3).
 
     Returns
@@ -387,7 +384,7 @@ def rgb2rgbcie(rgb):
 
     Parameters
     ----------
-    rgb : ndarray
+    rgb : array_like
         The image in RGB format, in a 3-D array of shape (.., .., 3).
 
     Returns
@@ -420,7 +417,7 @@ def rgbcie2rgb(rgbcie):
 
     Parameters
     ----------
-    rgbcie : ndarray
+    rgbcie : array_like
         The image in RGB CIE format, in a 3-D array of shape (.., .., 3).
 
     Returns
diff --git a/scikits/image/color/tests/test_colorconv.py b/scikits/image/color/tests/test_colorconv.py
index 9473b456..ac861555 100644
--- a/scikits/image/color/tests/test_colorconv.py
+++ b/scikits/image/color/tests/test_colorconv.py
@@ -57,9 +57,6 @@ class TestColorconv(TestCase):
     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]])
-
 
     # HSV to RGB
     def test_hsv2rgb_conversion(self):
@@ -77,9 +74,6 @@ class TestColorconv(TestCase):
     def test_hsv2rgb_error_one_element(self):
         self.assertRaises(ValueError, hsv2rgb, self.img_rgb[0,0])
 
-    def test_hsv2rgb_error_list(self):
-        self.assertRaises(TypeError, hsv2rgb, [self.img_rgb[0,0]])
-
 
     # RGB to XYZ
     def test_rgb2xyz_conversion(self):
@@ -101,9 +95,6 @@ class TestColorconv(TestCase):
     def test_rgb2xyz_error_one_element(self):
         self.assertRaises(ValueError, rgb2xyz, self.img_rgb[0,0])
 
-    def test_rgb2xyz_error_list(self):
-        self.assertRaises(TypeError, rgb2xyz, [self.img_rgb[0,0]])
-
 
     # XYZ to RGB
     def test_xyz2rgb_conversion(self):

From a93e5f9e6c195985385f936b281654619e601eb4 Mon Sep 17 00:00:00 2001
From: Ralf Gommers <rgommers@Ralf-Gommerss-iMac.local>
Date: Fri, 23 Oct 2009 10:51:53 +0200
Subject: [PATCH 15/16] Add color spaces work to contributors file.

---
 CONTRIBUTORS.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/CONTRIBUTORS.txt b/CONTRIBUTORS.txt
index 0f56ce4d..45836e7f 100644
--- a/CONTRIBUTORS.txt
+++ b/CONTRIBUTORS.txt
@@ -17,5 +17,5 @@
   OpenCV functions and better OSX library loader
 
 - Ralf Gommers
-  Image IO and plots in documentation
+  Image IO, color spaces and plots in documentation
 

From 04f01ffce4994452809cd58276ccf7ba3173217a Mon Sep 17 00:00:00 2001
From: Ralf Gommers <rgommers@Ralf-Gommerss-iMac.local>
Date: Fri, 23 Oct 2009 15:06:27 +0200
Subject: [PATCH 16/16] Add note on assumed data range.

---
 scikits/image/color/colorconv.py | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/scikits/image/color/colorconv.py b/scikits/image/color/colorconv.py
index d0ac2fbf..d7c5f4d2 100644
--- a/scikits/image/color/colorconv.py
+++ b/scikits/image/color/colorconv.py
@@ -133,6 +133,8 @@ def rgb2hsv(rgb):
 
     Notes
     -----
+    The conversion assumes an input data range of [0, 1] for all color components.
+
     Conversion between RGB and HSV color spaces results in some loss of
     precision, due to integer arithmetic and rounding [1]_.
 
@@ -205,6 +207,8 @@ def hsv2rgb(hsv):
 
     Notes
     -----
+    The conversion assumes an input data range of [0, 1] for all color components.
+
     Conversion between RGB and HSV color spaces results in some loss of
     precision, due to integer arithmetic and rounding [1]_.