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Old 27th Jul 2021, 8:26 am   #12
GMB
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Join Date: Aug 2003
Location: near Reading (and sometimes Torquay)
Posts: 2,634
Default Re: Scanning of Manuals & Circuit Diagrams?

DO NOT USE JPEG unless it is a photo of something in the real world.

AVOID FULL COLOUR as it is very bulky.

Ideally you want text and diagrams processed as 1-bit monochrome. But this may not be simple unless the original documents are nice and clear and black and scanned properly.

Pictures are tricky - you need to see how they were originally printed. They were often silk-screened so may work better than expected in mnochrome (at high resolution), but will look better if down-scaled and converted to grey-scale (or colour if it really is coloured).

Ideally you want to have separated out the different kinds of image, text/circuits and photos, so that these can be composed separately and combined back together to make your PDF. That way you can have a jpeg colour photo embedded in a page of monochrome text - and obtain optimal compression and clarity of the result.

Note that due to the way lossless compression is usually done in PDF you will still get fairly good compression if you have pasted a grey-scale photo into a monochrome page of text.
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