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One of the (many) advantages of compressing a scanned page with DjVu is that it de-duplicates characters:
…bitonal image compression that takes advantage of repetitions of nearly identical shapes on the page (such as characters) to efficiently compress text images.
Unfortunately, the PDF export feature of DjView (and its command-line counterpart ddvju
) throws away that advantage and renders a single image for each page. The result is that the PDF is usually 2 times as large as the DjVu file.
Seeing as the PDF format is more than capable of storing a picture once and displaying it many times in a page, I was wondering if there are any tools that generate an optimized PDF, preserving the DjVu compressed structure.
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Awesome! That's exactly what I needed. Using DjVuToy I can convert a 27MB DjVu into a 30MB PDF of the same resolution, as opposed to the 56MB PDF created by standard DjVu tools. This is a big size difference for many users. For anybody who is wondering where to get it, go to the author's homepage, click on the sticky blog post, and follow the link to the author's shared folder on Baidu. I opened it in a VM, because that's my policy with strange software, but it works well and seems legit.
– Tobia – 2018-01-15T10:36:54.720