Remove use of deprecated Pillow function

Fixes #170 by removing use of `PIL.Image.getdata()`.

Rather than using the suggested replacement of `get_flattened_data` which would,
require checking the version of Pillow, this uses `PIL.Image.tobytes()`,
which is available on all versions of Pillow.

`.tobytes` is also significantly faster, as it doesn't require Python list
iteration. Since the image is explicitly converted to "RGBA" format, the
bytes representation is just a linear list of the pixel values anyway.

Author: brianhelba

pixelmatch/contrib/PIL.py

@@ -79,12 +79,7 @@ def from_PIL_to_raw_data(pil_img: Image) -> MutableImageSequence:
     :param pil_img:
     :return:
     """
-    # getdata() returns ImagingCore which is iterable at runtime
-    return [
-        item
-        for sublist in pil_img.convert("RGBA").getdata()  # type: ignore[attr-defined]
-        for item in sublist
-    ]
+    return list(pil_img.convert("RGBA").tobytes())
 
 
 def to_PIL_from_raw_data(

test_pixelmatch.py

@@ -19,7 +19,7 @@ def pil_to_flatten_data(img):
     """
     Convert data from [(R1, G1, B1, A1), (R2, G2, B2, A2)] to [R1, G1, B1, A1, R2, G2, B2, A2]
     """
-    return [x for p in img.convert("RGBA").getdata() for x in p]
+    return list(img.convert("RGBA").tobytes())
 
 
 testdata = [