From 7ac3ae990fbd35fed011b50e3d545301e10eb229 Mon Sep 17 00:00:00 2001
From: Mihail Shinder <mihail@shinder.ml>
Date: Fri, 19 Nov 2021 10:34:00 +0200
Subject: [PATCH] Add unregistered CommandViewer

---
 src/PIL/ImageShow.py | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/src/PIL/ImageShow.py b/src/PIL/ImageShow.py
index cd0737c36..e6ea256f6 100644
--- a/src/PIL/ImageShow.py
+++ b/src/PIL/ImageShow.py
@@ -258,6 +258,26 @@ except ImportError:
 else:
     register(IPythonViewer)
 
+class CommandViewer(Viewer):
+    """
+    The viewer that use commands.
+    Should be suitable for any OS
+    """
+
+    def get_command(self, file, **options):
+        """
+        Substitute ``{}`` specifiers in ``command``
+        :param options: kwargs that should have 'command' in it
+        """
+
+        if not "command" in options:
+            raise TypeError("CommandViewer missing required keyword-only argument 'command'")
+        command = options["command"]
+        if not isinstance(command, str):
+            raise TypeError(f"'command' must be 'str' not '{type(command)}'")
+        values = {'file': file, **options}
+        return command.format(values)
+
 
 if __name__ == "__main__":