Google: Text In An Image Alt Attribute Within An H1 Is Within The H1

Google's John Mueller said on Twitter that text within an image's alt attribute is generally seen as text "as a part of the page where the image is embedded." If that text is within an H1 tag, then Google will also see it as part of the H1.

It is a bit of a confusing response, here it is within the context:

We tend to see text in image alt attributes as a part of the page where the image is embedded (as well as context for the image); if that's an image within a "h1", then that would be a part of the "h1". — 🍌 John 🍌 (@JohnMu) February 14, 2020

Just a little tidbit for you.

Forum discussion at Twitter.