"... the user should be in charge of this..."
As a user, I choose textmode. I use a text-only browser as an HTML reader, works great for EPUB. No graphical fonts, no Javascript, no CSS, no color. Often I will save to .txt so I can read with less(1).
As a user, I choose textmode. I use a text-only browser as an HTML reader, works great for EPUB. No graphical fonts, no Javascript, no CSS, no color. Often I will save to .txt so I can read with less(1).
Mostly, ebooks are perfectly fine to use without images, but not 100% of the time.
Below is a quick and dirty script I use to make a single HTML file from an EPUB file. It outputs a _script_ that when run will output the HTML files in the EPUB as a single file to stdout. It is not perfect, e.g., sometimes the order of the HTML files may need to be adjusted, but I rarely bother. I open the HTML file in links and optionally save as .txt. I don't care for UTF-8 or other non-ASCII characters.
EPUB to single HTML file.
#!/bin/sh
test ${#1} -ge 1||exec echo usage: $0 1.epub;
printf "(\n"
for x in ${1-*.epub};do
echo printf \'\\n\\n,,,,,,,,,,,,,,,,,,,,, "$x" ,,,,,,,,,,,,,,,,,,,,,,,\\n\\n\'
7z l $x|sed -n "s/.* /7z x -so $x /;/nav.xhtml/d;/[tx]ml$/p"|sort -n
done
echo ")|tr -cd '[\\\12\40-\176]'"