I have a habit of sending html emails to my friends. I usually rely on encryption provided by my protonmail account but occasionally I use less secure accounts as gmail and yahoo.
Would sending the body of the message in the form of an image increase my privacy and resistance to being surveiled? I'm mainly concerned with my email and phone number being scraped from the body of the message. When such a measure applied, would using different type of images, let's say jpeg instead of png, make a difference in their resistance to optical character recognition technology?
P.S. I write my emails in LaTeX, compile them to pdf files, and then I use the following code to create my images:
#!/usr/bin/bash
for f in *.pdf; do
pdftoppm -png -rx 1920 -ry 1080 ./"$f" ./"${f%.pdf}"
done
I think I'd class this as inappropriately paranoid.
Protonmail is great, no problem there. No matter what you do, when you send an email to a gmail account, they unavoidably know your email address, and from that they can index into their monstrous data reserves and link it up with not only your phone number, but pretty much everything about you, regardless of what you do within your email messages.
Technically speaking, for clean text on a plain background, PNG will look better, OCR better, and probably compress better than JPEG, but if you're out to hide stuff, overcompressed jpeg will make quite a mess and be harder to OCR, but also harder to read. However, considering that most text-based CAPTCHAs are now fairly easily defeated, nothing you do like this is likely to present any significant obstacle for the likes of google to read if they really want to.
The one thing you can of course do is to encrypt your messages with PGP or S/MIME. This will work fine in gmail; recipients won't be able to read messages in the web interface, but they will have no problem using an external encryption-capable email client (e.g. Thunderbird, Apple Mail, Outlook). Gmail will still of course see all the metadata relating to such messages, so if you're really that concerned, take the OPSEC route and simply don't ever send email to gmail (or gmail-hosted) addresses, or never include your phone number in messages (though that's probably not much of a defence anyway).