EPUB export: "Preserve Appearance" — function?

Forum|Forum|3 years ago
April 10, 2022
3 replies
608 views

The Object pane, under the Reflowable EPUB Export menu, leads off with a checkbox item, "Preserve Appearance from Layout." If you uncheck it, the "Use SVG as" option at the bottom is enabled.

I know a few things about EPUB export. I have experimented with this box checked and unchecked. I have searched the web and come up only with some vague, hand-waving discussion. And I am completely mystified as to what this option is supposed to control.

In hard technical terms and real effect, what does this export option do, besides enable/disable the SVG option?

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Frans v.d. Geest

Community Expert

James Gifford—NitroPressAuthor

Legend

Thanks! Pretty old, but it has some good clues. I think "Preserve Appearance" devolves to two settings in the advanced/individual settings, Rasterize Container and Rasterize Contents, but I need to do further experimenting.

This discussion seems to be concerned primarily with how the option affects the final file size, with "Preserve" bulking up the exported file with multiple copies of images. I don't know if that's changed since 2011, but my current workfile was 638k with "Use original image," 650k with "Preserve" and 638k with neither checked. Either the discussion was incorrect or the export process—bug?—has been fixed since then.

ETA: Wow, using Rasterize Container/Content on any images individually DOES bloat the file size.So I don't think either is connected (directly) to "Preserve."

In any case, I resolved my problem with that one image by unchecking both Preserve and Use Original, so that the rest of the images are handled the way I want, and then using Rasterize Container for that one cropped instance. Worked perfectly.

There is also an interesting... occurrence with scaling and border size. If you assign, say, a 1pt border to images in either ID object style or CSS, it varies widely with the various scaling options. I *suspect* that something like "rasterize container" is doing this (rasterize border and content image, then scale) and "rasterize contents" might leave the border at the defined width... but experimentation hilarity yet to ensue.

Still boggled that no one, including Big A, has ever discerned/defined exactly what this option does...

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James Gifford—NitroPressAuthor

Legend

Found a very slight/partial answer through serendipity.

This option is mutually exclusive with "Use Existing Image" although both can be deselected.
When I cropped a large image to allow a caption to fit onto the same page, with "Existing Image" checked, the frame remained the same size and the full image was oddly distorted within it. (Not squeezed vertically, but squeezed horizontally!)
When I switched to "Preserve Appearance," the cropped image and frame appeared correctly.
When I uncheck both, the cropped image and frame appear correctly.

So "Use Original Image" tends to let the image push the formatting around... but it's still not clear "Preserve Appearance" does anything but force-uncheck that and disable the SVG option setting. I'm leaning towards it being a menu-only control and having no actual function in the export.

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James Gifford—NitroPressAuthor

Legend

So, not even a wandering Dev can answer this question? 🙂

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