diff --git a/PIL/ImageShow.py b/PIL/ImageShow.py
index 23e0126a7..c8eeb2145 100644
--- a/PIL/ImageShow.py
+++ b/PIL/ImageShow.py
@@ -71,6 +71,7 @@ class Viewer(object):
             base = Image.getmodebase(image.mode)
         if base != image.mode and image.mode != "1" and image.mode != "RGBA":
             image = image.convert(base)
+        image.info['showing'] = True
 
         return self.show_image(image, **options)
 
diff --git a/PIL/PngImagePlugin.py b/PIL/PngImagePlugin.py
index 5e5eb14c7..0bcbd060f 100644
--- a/PIL/PngImagePlugin.py
+++ b/PIL/PngImagePlugin.py
@@ -687,6 +687,9 @@ def _save(im, fp, filename, chunk=putchunk, check=0):
             mode = "%s;%d" % (mode, bits)
 
     # encoder options
+    if (im.info.get('showing', False)):
+        im.encoderinfo['compress_level'] = 1
+        im.info.pop('showing', None)
     im.encoderconfig = (im.encoderinfo.get("optimize", False),
                         im.encoderinfo.get("compress_level", -1),
                         im.encoderinfo.get("compress_type", -1),