Is http://epubmaker.pglaf.org the same app the White Washers use for uploaded files? 

Some people at Distributed Proofreaders think the results are different between the http://epubmaker.pglaf.org/ results and the WW results published at PG.  I don't believe it but thought I'd ask here before submitting an opinion to the DP forum.

Specifically what they are claiming is that the oversized image (greater than 800 x 1200px or 128KB) reduction for the epub and mobi formats is different.

I can't answer the question, but as I recall the discussion it was about whether out-of-line (linked) images are included in the epub and mobi output files, not whether large images are reduced in size when included.

That is, some are saying that when the text includes a small image, which is linked to a larger version that the user can click on in a web browser, the epub/mobi files do not contain the larger images at all; only the smaller in-line ones. Others are saying the files contain both. And some are contending that it's different when we use ebookmaker.pglaf.org to generate the files, vs whatever the White Washers are doing to generate them.

But they are also talking about two different situations. One with the linked files, and another where @media queries are used to simply hide one file or the other depending on whether we're in a browser or in the epub/mobi version.

So it's really very confusing, to me.

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Walt