Simply, from a practital point iof view, my suggestion is: don't try to get a good djvu from IA pdf, use instead images (after conversion to jpg the images are very good), and the result will be much better - almost as good as images into IA viewer, that uses the same images. 


2016-05-13 10:06 GMT+02:00 Federico Leva (Nemo) <>:
Alex Brollo, 13/05/2016 09:02:
I presume that this complex structure is somewhat similar of djvu
background/foreground segmentation into djvu files, and artifacts are


So, pdf images are not only "compressed", but deeply processed and
segmented images.

...which is what I call "compression". I still recommend to try and increase the fixed-ppi parameter in such a case of excessive compression.

I also still need an answer to

Is something of this complex IA image processing path documented

What do you mean? Are you asking about details of their derivation plan for books? What we know has been summarised over time at , as always. As the help page IIRC states, the best way to understand what's going on is to check the item history and read the derive.php log, like which I linked.

The main difference compared to the past is, I think, that they're no longer creating the luratech b/w PDF, probably because the "normal" PDF now manages to compress enough. They may have not realised that the single PDF they now produce is too compressed for illustrations and for cases where the original JP2 is too small.


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