Avoid Windows path prefix for ImageMagick

beets/art.py

@@ -124,15 +124,23 @@ def check_art_similarity(log, item, imagepath, compare_threshold):
             is_windows = platform.system() == "Windows"
 
             # Converting images to grayscale tends to minimize the weight
-            # of colors in the diff score.
+            # of colors in the diff score. So we first convert both images
+            # to grayscale and then pipe them into the `compare` command.
+            # On Windows, ImageMagick doesn't support the magic \\?\ prefix
+            # on paths, so we pass `prefix=False` to `syspath`.
+            convert_cmd = [b'convert', syspath(imagepath, prefix=False),
+                           syspath(art, prefix=False),
+                           b'-colorspace', b'gray', b'MIFF:-']
+            compare_cmd = [b'compare', b'-metric', b'PHASH', b'-', b'null:']
+            log.debug(u'comparing images with pipeline {} | {}',
+                      convert_cmd, compare_cmd)
             convert_proc = subprocess.Popen(
-                [b'convert', syspath(imagepath), syspath(art),
-                 b'-colorspace', b'gray', b'MIFF:-'],
+                convert_cmd,
                 stdout=subprocess.PIPE,
                 close_fds=not is_windows,
             )
             compare_proc = subprocess.Popen(
-                [b'compare', b'-metric', b'PHASH', b'-', b'null:'],
+                compare_cmd,
                 stdin=convert_proc.stdout,
                 stdout=subprocess.PIPE,
                 stderr=subprocess.PIPE,

docs/changelog.rst

@@ -10,6 +10,8 @@ Some fixes for Windows:
 
 * Queries are now detected as paths when they contain backslashes (in
   addition to forward slashes). This only applies on Windows.
+* :doc:`/plugins/embedart`: Image similarity comparison with ImageMagick
+  should now work on Windows.
 
 Fixes: