Is it possible to make an image appear as fullscreen in all major e-pub readers (at least when viewed on tablets and smart phones)?
I've been asked to make an E-pub conversion of an image-heavy book with full-page images on some pages and only text on other pages. I'll divide every chapter into one text portion that can flow freely from page to page and then place all of the relevant images at the end of each chapter (with page-break-before:always to guarantee that each image appears on its own). The reading experience would be greatly improved if these images would pop up as fullscreen images. Is this possible for example with javascript?
A second question would be if it's possible to have many thumbnails appear on the same page upon which the user could select which one to view in full-screen mode (kind of like a lightbox). I have a little experience with javascript but I don't know how well supported it is in epub readers and wether the standard web solutions would work.
In short: it is not possible to do what you ask for, and be sure it will work on any possible reading system.
JS is supported only by an handful of RS, essentially iBooks and (to some extent) Readium.
If you need exact placement of images and graphics, craft a FXL EPUB.