You can write an Invisible Secret Text Message in an Image File, by following this trick laid down in this post. All you need is the Notepad!

Here’s how it works. How to insert a text box in Google Docs Within Google Docs there is a pop-up version of Google Draw that allows you to insert shapes, text boxes and drawings into your document.

Alt text is added to an image or site's metadata, and generally is only readable to screen readers or other assistive technology, not users directly.