Simplify output handling for binary morphology.

skimage/morphology/binary.py

@@ -3,46 +3,15 @@ import numpy as np
 from scipy import ndimage
 
 
-def _convolve(image, selem, out, cval):
-
-    # determine the smallest integer dtype which does not overflow
-    selem = selem != 0
-    selem_sum = np.sum(selem)
-    if selem_sum < 2 ** 8:
-        out_dtype = np.uint8
-    else:
-        out_dtype = np.intp
-
-    if out is None:
-        out = np.zeros_like(image, dtype=out_dtype)
-    else:
-        warnings.warn('Parameter `out` is deprecated and it does not equal '
-                      'the output image if the sum of the structuring element '
-                      'overflows the dtype of `out`.')
-        iinfo = np.iinfo(out.dtype)
-        if iinfo.max - iinfo.min < selem_sum:
-            raise ValueError('Sum of structuring (=%d) element results in '
-                             'overflow for dtype of `out`. You must raise the '
-                             'bit-depth.')
-
-    conv = ndimage.convolve(image > 0, selem, output=out,
-                            mode='constant', cval=cval)
-
-    if conv is not None:
-        out = conv
-
-    return out, selem_sum
-
-
 def binary_erosion(image, selem, out=None):
     """Return fast binary morphological erosion of an image.
 
     This function returns the same result as greyscale erosion but performs
     faster for binary images.
 
-    Morphological erosion sets a pixel at (i,j) to the minimum over all pixels
-    in the neighborhood centered at (i,j). Erosion shrinks bright regions and
-    enlarges dark regions.
+    Morphological erosion sets a pixel at ``(i,j)`` to the minimum over all
+    pixels in the neighborhood centered at ``(i,j)``. Erosion shrinks bright
+    regions and enlarges dark regions.
 
     Parameters
     ----------
@@ -50,20 +19,20 @@ def binary_erosion(image, selem, out=None):
         Image array.
     selem : ndarray
         The neighborhood expressed as a 2-D array of 1's and 0's.
-    out : ndarray
+    out : ndarray of bool
         The array to store the result of the morphology. If None is
         passed, a new array will be allocated.
 
     Returns
     -------
-    eroded : bool array
+    eroded : ndarray of bool
         The result of the morphological erosion.
 
     """
-
-    out, selem_sum = _convolve(image, selem, out, 1)
-    return np.array(np.equal(out, selem_sum, out=out), dtype=np.bool,
-                    copy=False)
+    selem = (selem != 0)
+    selem_sum = np.sum(selem)
+    out = ndimage.convolve(image > 0, selem, mode='constant', cval=1)
+    return np.equal(out, selem_sum, out=out)
 
 
 def binary_dilation(image, selem, out=None):
@@ -83,19 +52,19 @@ def binary_dilation(image, selem, out=None):
         Image array.
     selem : ndarray
         The neighborhood expressed as a 2-D array of 1's and 0's.
-    out : ndarray
+    out : ndarray of bool
         The array to store the result of the morphology. If None, is
         passed, a new array will be allocated.
 
     Returns
     -------
-    dilated : bool array
+    dilated : ndarray of bool
         The result of the morphological dilation.
 
     """
-
-    out, _ = _convolve(image, selem, out, 0)
-    return np.array(np.not_equal(out, 0, out=out), dtype=np.bool, copy=False)
+    selem = (selem != 0)
+    out = ndimage.convolve(image > 0, selem, mode='constant', cval=0)
+    return np.not_equal(out, 0, out=out)
 
 
 def binary_opening(image, selem, out=None):
@@ -115,17 +84,16 @@ def binary_opening(image, selem, out=None):
         Image array.
     selem : ndarray
         The neighborhood expressed as a 2-D array of 1's and 0's.
-    out : ndarray
+    out : ndarray of bool
         The array to store the result of the morphology. If None
         is passed, a new array will be allocated.
 
     Returns
     -------
-    opening : bool array
+    opening : ndarray of bool
         The result of the morphological opening.
 
     """
-
     eroded = binary_erosion(image, selem)
     out = binary_dilation(eroded, selem, out=out)
     return out
@@ -148,13 +116,13 @@ def binary_closing(image, selem, out=None):
         Image array.
     selem : ndarray
         The neighborhood expressed as a 2-D array of 1's and 0's.
-    out : ndarray
+    out : ndarray of bool
         The array to store the result of the morphology. If None,
         is passed, a new array will be allocated.
 
     Returns
     -------
-    closing : bool array
+    closing : ndarray of bool
         The result of the morphological closing.
 
     """

skimage/morphology/tests/test_binary.py

@@ -17,27 +17,6 @@ def test_non_square_image():
     testing.assert_array_equal(binary_res, grey_res)
 
 
-def test_selem_overflow():
-    strel = np.ones((17, 17), dtype=np.uint8)
-    img = np.zeros((20, 20))
-    img[2:19, 2:19] = 1
-    binary_res = binary.binary_erosion(img, strel)
-    grey_res = img_as_bool(grey.erosion(img, strel))
-    testing.assert_array_equal(binary_res, grey_res)
-
-
-def test_selem_overflow_exception():
-    strel = np.ones((17, 17), dtype=np.uint8)
-    img = np.zeros((20, 20))
-    img[2:19, 2:19] = 1
-    out = np.zeros((20, 20), dtype=np.uint8)
-    testing.assert_raises(ValueError, binary.binary_erosion, img, strel, out)
-    out = np.zeros((20, 20), dtype=np.uint16)
-    binary_res = binary.binary_erosion(img, strel, out=out)
-    grey_res = img_as_bool(grey.erosion(img, strel))
-    testing.assert_array_equal(binary_res, grey_res)
-
-
 def test_binary_erosion():
     strel = selem.square(3)
     binary_res = binary.binary_erosion(bw_lena, strel)