HTTPS page links to HTTP image Description & How to Fix
This issue is an instance of mixed content that occurs when HTML pages load over a secure HTTPS connection but link to resources (images, CSS, or JS) over an insecure HTTP connection.
Mixed content degrades the security and user experience of your HTTPS site.
Some browsers block insecure resource requests by default. If your page depends on these insecure resources, then your page might not work properly when they get blocked.
How to fix
For your own domain, serve all content as HTTPS and fix your links. Often, the HTTPS version of the content already exists and this just requires adding an "s" to links - http:// to https://.
For images hosted on other domains, use the site's HTTPS version if available. If HTTPS is not available, you can try contacting the domain and asking them if they can make the content available via HTTPS.