Automatic masks range selection for better visualization (#20)

* Update app.py

The range of the mask needs to be changed.

* Automatic masks range selection for better visualization

Co-authored-by: Konstantin Sofiiuk <sofiyuk@gmail.com>

Author: TwistedW

interactive_demo/app.py

@@ -208,6 +208,8 @@ def _save_mask_callback(self):
             mask = self.controller.result_mask
             if mask is None:
                 return
+            if 0 < mask.max() < 256:
+                mask *= 255 // mask.max()
 
             filename = filedialog.asksaveasfilename(parent=self.master, initialfile='{}.png'.format(self.filename), filetypes=[
                 ("PNG image", "*.png"),