Merge pull request cupy#3559 from pmixer/patch-1

add piece of sample code for image resizing

docs/source/reference/ndimage.rst

@@ -42,4 +42,25 @@ Measurements
 OpenCV mode
 -----------
 :mod:`cupyx.scipy.ndimage` supports additional mode, ``opencv``.
-If it is given, the function performs like `cv2.warpAffine <https://docs.opencv.org/master/da/d54/group__imgproc__transform.html#ga0203d9ee5fcd28d40dbc4a1ea4451983>`_ or `cv2.resize <https://docs.opencv.org/master/da/d54/group__imgproc__transform.html#ga47a974309e9102f5f08231edc7e7529d>`_.
+If it is given, the function performs like `cv2.warpAffine <https://docs.opencv.org/master/da/d54/group__imgproc__transform.html#ga0203d9ee5fcd28d40dbc4a1ea4451983>`_ or `cv2.resize <https://docs.opencv.org/master/da/d54/group__imgproc__transform.html#ga47a974309e9102f5f08231edc7e7529d>`_. Example:
+
+
+.. code:: python
+
+   import cupyx.scipy.ndimage
+   import cupy as cp
+   import cv2
+
+   im = cv2.imread('TODO') # pls fill in your image path
+
+   trans_mat = cp.eye(4)
+   trans_mat[0][0] = trans_mat[1][1] = 0.5
+
+   smaller_shape = (im.shape[0] // 2, im.shape[1] // 2, 3)
+   smaller = cp.zeros(smaller_shape) # preallocate memory for resized image
+
+   cupyx.scipy.ndimage.affine_transform(im, trans_mat, output_shape=smaller_shape,
+                                        output=smaller, mode='opencv')
+
+   cv2.imwrite('smaller.jpg', cp.asnumpy(smaller)) # smaller image saved locally
+