Hello, I use your plugin and find it useful.
However, I am in the process of making my entire site encrypted and have secured a Third Party SSL cert and everything is good there. I have worked through my plugins and your plugin has one little bug. It still loads the http:// version of default.png for default images even after clearing cache and re-indexing. If I go to https location of the file, it finds it and loads, Here is what Chrome sees when I inspect the image:
As you can see the src is pulling the standard http, but the srcset is correctly identifying https as what it should be using. Can you please fix this and release a patch so your plugin is 100% ssl compatible?