Update app.py

app.py

@@ -25,7 +25,8 @@ def image_download_button(pil_image, filename: str, fmt: str, label="Download"):
     mime = "image/png"
 
     buf = BytesIO()
-    pil_image.save(buf, format=pil_format)
+    pil_image.save(buf, format='PNG')
+
     
     return st.download_button(
         label=label,