Properly converted PDF and ePUB shouldn't be much larger than the pictures alone. It should be possible to create a PDF with no margins at all (but if the aspect ratio is not the same as the screen, you'll see some margin, of coures). With ePub it needs more fiddling, but by adding "@page { margin: 0 }" to the CSS you can probably remove some of it (the rest through standard CSS margins). Wrapping each image in SVG may give you more control with scaling.
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