univurshul wrote:How large are the files sizes of the djvu completed ebooks vs. a conventionally built PDF?
If we're talking a file created from scanned images, a djvu file will be significantly smaller in size. Djvu was made specifically for scanned images and makes use of jb2 compression, whereas the best compression for a pdf is Group4. In addition, minidjvu will create a shared dictionary for multiple images, which reduces the file size further. I know that isn't an in-depth explanation, but it should give you enough to start exploring with Google.
A while ago I scanned a 545 page book, completely bitonal (black and white) except for the front cover which was full color. The pdf version of it was 37.5 MB, excluding
the cover and ocr. The djvu version was 12.8 MB, including
cover and ocr. Later I remade the djvu with minidjvu, which came to 6.2 MB, including cover and ocr. So, quite significant.
On the other hand, if the book is not scanned but created from another computer program like Scribus or OpenOffice, djvu shouldn't even be an option. Djvu is a container for compressed images, unlike pdf's which can also represent images from document data (such as put this text in this font in this size here).
univurshul wrote:High resolution?
Non-issue. Both djvu and pdf can contain images at whatever resolution they want as far as I am aware.
univurshul wrote:Faster Rendering on iPads?
Now that's an interesting question. I couldn't find anything on differences in rendering speed between pdf's and djvu files. My money would be on djvu since it is working with a smaller file size to begin with. Ultimately, though, I think this would need to be a comparison of compression codecs, i.e. how does jb2's decoding speed compare to Group4 or LZW or any of the others.
I forgot to mention that several months ago I heard of a new compression for pdf's that is very similar to jb2 and would produce similar file sizes. For the life of me I can't remember the name of it. I do remember that there was a big issue of it being encumbered by patents. If it does take off, it would probably be a few years before it makes it into pdf reader software, and who knows when it would be accessible in the open source world if there are patent questions.