How Do I Convert PDF to Djvu?

How do I convert PDF to DjVu?

Think of PDF as a wrapper for several different raster formats. Most simple publishing programs simply take the image compress it to conventional JPEG and stick in the PDF wrapper. So, your PDF file ends up being a tiny bit bigger than the JPEG file. JPEG files are great for low-resolution color photographs. To get adequate fidelity of text you need a larger JPEG file. DjVu has a "mixed raster content model" so it can store the color part of the image at relatively low resolution (think of the color of the page or a small photograph next to the text) using a compression technique similar to JPEG20000 and the black and white text at high resolution using a different technique. That's why, for certain classes of documents we can create shockingly small DjVu files that look so good. PDF has come a long way since DjVu was invented and can actually support the same Mixed Raster Content Model as DjVu using superior compression techniques. I know a long time ago there was commercialization attempts to sell programs that did this. I don't recall any of them really catching on.