Fixed database typo and removed unnecessary class identifier.

venv/Lib/site-packages/skimage/util/compare.py

@@ -0,0 +1,60 @@
+import numpy as np
+from ..util import img_as_float
+from itertools import product
+
+
+def compare_images(image1, image2, method='diff', *, n_tiles=(8, 8)):
+    """
+    Return an image showing the differences between two images.
+
+    .. versionadded:: 0.16
+
+    Parameters
+    ----------
+    image1, image2 : 2-D array
+        Images to process, must be of the same shape.
+    method : string, optional
+        Method used for the comparison.
+        Valid values are {'diff', 'blend', 'checkerboard'}.
+        Details are provided in the note section.
+    n_tiles : tuple, optional
+        Used only for the `checkerboard` method. Specifies the number
+        of tiles (row, column) to divide the image.
+
+    Returns
+    -------
+    comparison : 2-D array
+        Image showing the differences.
+
+    Notes
+    -----
+    ``'diff'`` computes the absolute difference between the two images.
+    ``'blend'`` computes the mean value.
+    ``'checkerboard'`` makes tiles of dimension `n_tiles` that display
+    alternatively the first and the second image.
+    """
+    if image1.shape != image2.shape:
+        raise ValueError('Images must have the same shape.')
+
+    img1 = img_as_float(image1)
+    img2 = img_as_float(image2)
+
+    if method == 'diff':
+        comparison = np.abs(img2 - img1)
+    elif method == 'blend':
+        comparison = 0.5 * (img2 + img1)
+    elif method == 'checkerboard':
+        shapex, shapey = img1.shape
+        mask = np.full((shapex, shapey), False)
+        stepx = int(shapex / n_tiles[0])
+        stepy = int(shapey / n_tiles[1])
+        for i, j in product(range(n_tiles[0]), range(n_tiles[1])):
+            if (i + j) % 2 == 0:
+                mask[i * stepx:(i + 1)*stepx, j * stepy:(j + 1) * stepy] = True
+        comparison = np.zeros_like(img1)
+        comparison[mask] = img1[mask]
+        comparison[~mask] = img2[~mask]
+    else:
+        raise ValueError('Wrong value for `method`. '
+                         'Must be either "diff", "blend" or "checkerboard".')
+    return comparison