JBIG2 is a mutlipage image format, but is different from - for example - multipage tiff because the images are not independently compressed. They share compression data, specifically a symbol dictionary.
There are three possible approaches here: 1. Have Tesseract accept JBIG2 images produced by jbig2enc and embed them into PDF without modification, 2. Have Tesseract actually do JBIG2 compression. 3. Have Tesseract do image segmentation, compress some parts of the page as JBIG2, other parts as JP2K, and store the results in PDF in a mixed raster format. I'm only going to discuss #1 because it is simplest and matches the current 'try to never transcode' philosophy. We'd need a JBIG2 decoder in Leptonica. That's probably straightforward but still a very solid chunk of work. Then, there is what to do in Tesseract. The PDF rendering module would need to learn about the symbol dictionary (or dictionaries) and add it to collection of PDF objects. It will need an understanding of what's going on much better than what we currently use, which is simply 'Hey, what image file belongs to this page? Let's try to inline it unchanged,' https://github.com/tesseract-ocr/tesseract/blob/master/api/pdfrenderer.cpp#L811 Now the good news is the PDF rendering module is really small and is not cemented down by a whole bunch of unnecessary abstraction layers. And I know it's possible because I've personally done it with colleagues elsewhere. But it is a pretty significant effort, and I'm honestly not sure it's worth putting inside Tesseract. Maybe a better approach is post processing, with a PDF to PDF converter that uses approach #3. This is the winning strategy for Linearization, which can be done on a Tesseract produced PDF using QPDF. -- You received this message because you are subscribed to the Google Groups "tesseract-ocr" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/tesseract-ocr. To view this discussion on the web visit https://groups.google.com/d/msgid/tesseract-ocr/0f9e6702-a759-4053-b9be-42bc96c1d547%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
