It is possible to use an image in a hyperlink, such as
The gif would contain the text, look like a button, is lossless, and would have no transparency. This works on all Previewer modes. The image class would of course be centered. The point is that it won't resize with increasing font size.
Is this ever done? Is it suitable for e-books, or more like plaid slacks?
This will work. I don't know if it would necessarily be obvious to a reader that they could interact with the book in this way, but that would of course depend entirely on the way it is presented and the reading audience.
It is actually possible to scale images relative to text size in Kindle Format 8 (KF8) only. This can be done by setting the height in em units. So for example, the following CSS would make the image approximately the height of one line of text:
For images sized to 1em should work very well. In cases with very wide images, or larger em lengths, there may be some interaction issues when the image becomes wider than the screen width minus margin. I have yet to investigate that far enough to recommend it. Definitely test, test, test, and then test some more if you do want to try this technique. And do your testing on actual Kindles/reader apps, rather than relying on Kindle Previewer.
Thanks for that, I wasn't aware of this KF8 ability. Definitely something to salt away, could be very handy in the right situation.
Even though an image could (I think) be contrived such that one could hardly resist clicking on it, I have abandoned the idea. Its the pseudo-pushbutton's plaid slacks to the Kindle's bowler, it just looks out of place.