When using get_serving_url(user.photoBlobKey) to return an image URL from the GAE Blobstore, the Google Images API returns a JPEG image with quality = 70 and size = 512px as default.
Is there any way to increase the default JPEG quality returned by get_serving_url()?
No there is not.
If you think it’s a useful feature you can add an item to the issue tracker, from there the team will assess the demand for implementing it.