Backport PR matplotlib#18185: FIX: fix reading from http/https urls via imread

Author: QuLogic

lib/matplotlib/__init__.py

@@ -760,11 +760,18 @@ def is_url(filename):
     return URL_REGEX.match(filename) is not None
 
 
+@functools.lru_cache()
+def _get_ssl_context():
+    import certifi
+    import ssl
+    return ssl.create_default_context(cafile=certifi.where())
+
+
 @contextlib.contextmanager
 def _open_file_or_url(fname):
     if not isinstance(fname, Path) and is_url(fname):
         import urllib.request
-        with urllib.request.urlopen(fname) as f:
+        with urllib.request.urlopen(fname, context=_get_ssl_context()) as f:
             yield (line.decode('utf-8') for line in f)
     else:
         fname = os.path.expanduser(fname)

lib/matplotlib/image.py

@@ -8,7 +8,6 @@
 import logging
 from numbers import Number
 from pathlib import Path
-import urllib.parse
 
 import numpy as np
 import PIL.PngImagePlugin
@@ -1443,9 +1442,12 @@ def imread(fname, format=None):
         - (M, N, 3) for RGB images.
         - (M, N, 4) for RGBA images.
     """
+    # hide imports to speed initial import on systems with slow linkers
+    from urllib import parse
+
     if format is None:
         if isinstance(fname, str):
-            parsed = urllib.parse.urlparse(fname)
+            parsed = parse.urlparse(fname)
             # If the string is a URL (Windows paths appear as if they have a
             # length-1 scheme), assume png.
             if len(parsed.scheme) > 1:
@@ -1468,10 +1470,18 @@ def imread(fname, format=None):
     img_open = (
         PIL.PngImagePlugin.PngImageFile if ext == 'png' else PIL.Image.open)
     if isinstance(fname, str):
-        parsed = urllib.parse.urlparse(fname)
+
+        parsed = parse.urlparse(fname)
         if len(parsed.scheme) > 1:  # Pillow doesn't handle URLs directly.
+            # hide imports to speed initial import on systems with slow linkers
             from urllib import request
-            with urllib.request.urlopen(fname) as response:
+            with request.urlopen(fname,
+                                 context=mpl._get_ssl_context()) as response:
+                import io
+                try:
+                    response.seek(0)
+                except (AttributeError, io.UnsupportedOperation):
+                    response = io.BytesIO(response.read())
                 return imread(response, format=ext)
     with img_open(fname) as image:
         return (_pil_png_to_float_array(image)

lib/matplotlib/testing/conftest.py

@@ -16,6 +16,7 @@ def pytest_configure(config):
         ("markers", "style: Set alternate Matplotlib style temporarily."),
         ("markers", "baseline_images: Compare output against references."),
         ("markers", "pytz: Tests that require pytz to be installed."),
+        ("markers", "network: Tests that reach out to the network."),
         ("filterwarnings", "error"),
     ]:
         config.addinivalue_line(key, value)

lib/matplotlib/tests/test_image.py

@@ -1111,3 +1111,9 @@ def test_exact_vmin():
 
     # check than the RBGA values are the same
     assert np.all(from_image == direct_computation)
+
+
+@pytest.mark.network
+@pytest.mark.flaky
+def test_https_imread_smoketest():
+    v = mimage.imread('https://matplotlib.org/1.5.0/_static/logo2.png')

requirements/testing/travis_all.txt

@@ -1,5 +1,6 @@
 # pip requirements for all the travis builds
 
+certifi
 coverage
 pytest!=4.6.0,!=5.4.0
 pytest-cov

setup.py

@@ -278,6 +278,7 @@ def build_extensions(self):
         "numpy>=1.15",
     ],
     install_requires=[
+        "certifi>=2020.06.20",
         "cycler>=0.10",
         "kiwisolver>=1.0.1",
         "numpy>=1.15",