CLI brother_ql print: use click.File() to allow input from stdin

brother_ql/cli.py

@@ -120,7 +120,7 @@ def env(ctx, *args, **kwargs):
     print("\n##################\n")
 
 @cli.command('print', short_help='Print a label')
-@click.argument('images', nargs=-1, metavar='IMAGE [IMAGE] ...')
+@click.argument('images', nargs=-1, type=click.File('rb'), metavar='IMAGE [IMAGE] ...')
 @click.option('-l', '--label', type=click.Choice(label_sizes), envvar='BROTHER_QL_LABEL', help='The label (size, type - die-cut or endless). Run `brother_ql info labels` for a full list including ideal pixel dimensions.')
 @click.option('-r', '--rotate', type=click.Choice(('auto', '0', '90', '180', '270')), default='auto', help='Rotate the image (counterclock-wise) by this amount of degrees.')
 @click.option('-t', '--threshold', type=float, default=70.0, help='The threshold value (in percent) to discriminate between black and white pixels.')

brother_ql/conversion.py

@@ -79,10 +79,11 @@ def convert(qlr, images, label,  **kwargs):
     for image in images:
         if isinstance(image, Image.Image):
             im = image
-        elif isinstance(image, str):
-            im = Image.open(image)
         else:
-            raise NotImplementedError("The image argument needs to be an Image() instance or the filename to an image.")
+            try:
+                im = Image.open(image)
+            except:
+                raise NotImplementedError("The image argument needs to be an Image() instance, the filename to an image, or a file handle.")
 
         if im.mode.endswith('A'):
             # place in front of white background and get red of transparency