Fix error with loading paletted BMP images using Pillow (#388)

* Create test that fails to load a paletted BMP image in Pillow

* Apply hacky fix to allow loading paletted BMPs

* Swap axes for BGR modes

* Final touches to get it working when PR is made

* Add name to contributors

* Small change

Should force CI to rerun and succeed...

* Remove variable assignments

Not used, caused error in CI

* Reformatted files using black

Believe it is causing issues with getting CI to pass

CONTRIBUTORS.txt

@@ -49,3 +49,6 @@
 
 - Zulko
   Various contribution related to the ffmpeg plugin.
+
+- Addison Elliott
+  Add support for 8-bit paletted BMPs

imageio/core/fetching.py

@@ -161,7 +161,7 @@ def _fetch_file(url, file_name, print_destination=True):
     for tries in range(4):
         try:
             # Checking file size and displaying it alongside the download url
-            remote_file = urlopen(url, timeout=5.)
+            remote_file = urlopen(url, timeout=5.0)
             file_size = int(remote_file.headers["Content-Length"].strip())
             size_str = _sizeof_fmt(file_size)
             print("Try %i. Download from %s (%s)" % (tries + 1, url, size_str))

imageio/plugins/ffmpeg.py

@@ -563,12 +563,16 @@ def _load_infos(self):
                 if self.request._video:
                     ffmpeg_err = (
                         "FFMPEG STDERR OUTPUT:\n"
-                        + self._stderr_catcher.get_text(.1)
+                        + self._stderr_catcher.get_text(0.1)
                         + "\n"
                     )
                     if "darwin" in sys.platform:
                         if "Unknown input format: 'avfoundation'" in ffmpeg_err:
-                            ffmpeg_err += "Try installing FFMPEG using " "home brew to get a version with " "support for cameras."
+                            ffmpeg_err += (
+                                "Try installing FFMPEG using "
+                                "home brew to get a version with "
+                                "support for cameras."
+                            )
                     raise IndexError(
                         "No video4linux camera at %s.\n\n%s"
                         % (self.request._video, ffmpeg_err)

imageio/plugins/pillow.py

@@ -122,6 +122,13 @@ def _open(self, pilmode=None, as_gray=False):
             self._im = factory(self._fp, "")
             if hasattr(Image, "_decompression_bomb_check"):
                 Image._decompression_bomb_check(self._im.size)
+            # Save the raw mode used by the palette for a BMP because it may not be the number of channels
+            # When the data is read, imageio hands the palette to PIL to handle and clears the rawmode argument
+            # However, there is a bug in PIL with handling animated GIFs with a different color palette on each frame.
+            # This issue is resolved by using the raw palette data but the rawmode information is now lost. So we
+            # store the raw mode for later use
+            if self._im.palette and self._im.palette.dirty:
+                self._im.palette.rawmode_saved = self._im.palette.rawmode
             pil_try_read(self._im)
             # Store args
             self._kwargs = dict(
@@ -161,6 +168,8 @@ def _get_data(self, index):
                 while i < index:  # some formats need to be read in sequence
                     i += 1
                     self._seek(i)
+            if self._im.palette and self._im.palette.dirty:
+                self._im.palette.rawmode_saved = self._im.palette.rawmode
             self._im.getdata()[0]
             im = pil_get_frame(self._im, **self._kwargs)
             return im, self._im.info
@@ -556,14 +565,21 @@ def pil_get_frame(im, is_gray=None, as_gray=None, mode=None, dtype=None):
             frame = im.convert("RGBA")
         elif im.palette.mode in ("RGB", "RGBA"):
             # We can do this ourselves. Pillow seems to sometimes screw
-            # this up if a  multi-gif has a pallete for each frame ...
+            # this up if a  multi-gif has a palette for each frame ...
             # Create palette array
             p = np.frombuffer(im.palette.getdata()[1], np.uint8)
+            # Restore the raw mode that was saved to be used to parse the palette
+            if hasattr(im.palette, "rawmode_saved"):
+                im.palette.rawmode = im.palette.rawmode_saved
+            mode = im.palette.rawmode if im.palette.rawmode else im.palette.mode
+            nchannels = len(mode)
             # Shape it.
-            nchannels = len(im.palette.mode)
             p.shape = -1, nchannels
-            if p.shape[1] == 3:
-                p = np.column_stack((p, 255 * np.ones(p.shape[0], p.dtype)))
+            if p.shape[1] == 3 or (p.shape[1] == 4 and mode[-1] == "X"):
+                p = np.column_stack((p[:, :3], 255 * np.ones(p.shape[0], p.dtype)))
+            # Swap the axes if the mode is in BGR and not RGB
+            if mode.startswith("BGR"):
+                p = p[:, [2, 1, 0]] if p.shape[1] == 3 else p[:, [2, 1, 0, 3]]
             # Apply palette
             frame_paletted = np.array(im, np.uint8)
             try:

tests/test_pillow.py

@@ -367,6 +367,15 @@ def test_inside_zipfile():
         imageio.imread(fname + "/" + name)
 
 
+def test_bmp():
+    need_internet()
+    fname = get_remote_file("images/scribble_P_RGB.bmp", test_dir)
+
+    imageio.imread(fname)
+    imageio.imread(fname, pilmode="RGB")
+    imageio.imread(fname, pilmode="RGBA")
+
+
 def test_scipy_imread_compat():
     # https://docs.scipy.org/doc/scipy/reference/generated/scipy.misc.imread.html
     # https://github.com/scipy/scipy/blob/41a3e69ca3141d8bf996bccb5eca5fc7bbc21a51/scipy/misc/pilutil.py#L111
@@ -402,4 +411,5 @@ def test_scipy_imread_compat():
     # test_inside_zipfile()
     # test_png()
     # test_animated_gif()
+    # test_bmp()
     run_tests_if_main()