icat kitten: Add support for displaying images at http(s) URLs

Fixes #1340

docs/changelog.rst

@@ -6,6 +6,8 @@ Changelog
 0.13.4 [future]
 ---------------------
 
+- icat kitten: Add support for displaying images at http(s) URLs (:iss:`1340`)
+
 - A new option :opt:`strip_trailing_spaces` to optionally remove trailing
   spaces from lines when copying to clipboard.
 

kittens/icat/main.py

@@ -318,6 +318,7 @@ def main(args=sys.argv):
         if len(items) > 1 or (isinstance(items[0], str) and os.path.isdir(items[0])):
             raise SystemExit(f'The --place option can only be used with a single image, not {items}')
         sys.stdout.buffer.write(b'\0337')  # save cursor
+    url_pat = re.compile(r'https?://', flags=re.I)
     for item in items:
         is_tempfile = False
         try:
@@ -326,11 +327,22 @@ def main(args=sys.argv):
                 tf.write(item), tf.close()
                 item = tf.name
                 is_tempfile = True
-            if os.path.isdir(item):
-                for x in scan(item):
-                    process(item, args)
-            else:
+            if url_pat.match(item) is not None:
+                from urllib.request import urlretrieve
+                with NamedTemporaryFile(prefix='url-image-data-', delete=False) as tf:
+                    try:
+                        urlretrieve(item, filename=tf.name)
+                    except Exception as e:
+                        raise SystemExit('Failed to download image at URL: {} with error: {}'.format(item, e))
+                    item = tf.name
+                is_tempfile = True
                 process(item, args, is_tempfile)
+            else:
+                if os.path.isdir(item):
+                    for x in scan(item):
+                        process(item, args)
+                else:
+                    process(item, args, is_tempfile)
         except NoImageMagick as e:
             raise SystemExit(str(e))
         except ConvertFailed as e: