image resize in parallel script

images_resize.py

@@ -0,0 +1,65 @@
+import argparse
+from functools import partial
+from multiprocessing import Pool, cpu_count
+import pathlib
+import cv2
+import numpy as np
+import skimage.transform as transform
+
+
+def mp_parallel_map(func, inputs, processes_count=-1):
+    processes_count = processes_count if processes_count > 0 else cpu_count()
+    processes_count = min(processes_count, len(inputs))
+    with Pool(processes=processes_count) as pool:
+        return list(pool.map(func, inputs))
+
+
+def one_true(iterable):
+    it = iter(iterable)
+    return any(it) and not any(it)
+
+
+def read_rescale_write(
+    image_path: pathlib.Path,
+    output_folder: pathlib.Path,
+    num_pixels: int,
+    rescale: float,
+):
+    img = cv2.imread(str(image_path))
+    scale = rescale if rescale else float(num_pixels) / max(img.shape[:2])
+    rescaled_img = transform.rescale(
+        img,
+        scale,
+        channel_axis=2,
+        anti_aliasing=True,
+        preserve_range=True
+    ).astype(np.uint8)
+    cv2.imwrite(str(output_folder / image_path.name), rescaled_img)
+
+
+def get_args():
+    parser = argparse.ArgumentParser()
+    parser.add_argument("-i", "--input", type=pathlib.Path, required=True, help="folder with tif files.")
+    parser.add_argument("-o", "--output", type=pathlib.Path, default=None, help="folder to write to.")
+    parser.add_argument("-p", "--num_pixels", type=int, help="number of pixels for the bigger axis.")
+    parser.add_argument("-r", "--rescale", type=float, help="rescale factor to rescale the image.")
+
+    return parser.parse_args()
+
+
+if __name__ == '__main__':
+    args = get_args()
+
+    if not args.output: args.output: pathlib.Path = args.input
+    args.output.mkdir(exist_ok=True, parents=True)
+
+    assert one_true((args.num_pixels, args.rescale)), "you need to choose either number of "\
+                                                      "pixels or rescale factor but not both"
+
+    p_read_rescale_write = partial(read_rescale_write,
+            output_folder=args.output,
+            num_pixels=args.num_pixels,
+            rescale=args.rescale)
+
+    mp_parallel_map(p_read_rescale_write, list(args.input.glob('*')))
+