Big old scanned manuals to small old scanned manuals

It is good that there are so many scanned manuals for old computer systems out there. Every old system did things its very own special way, and life’s too short to guess. I mean, there’s not much out there on the SYM-1 I’m trying to get working again:

— not much except for 6502.org’s excellent Synertek SYM-1 Resources, that is.

Some manuals, though, while lovingly scanned, are just too large to download, browse or file. Take, for instance, AppleIIScans’ Apple II BASIC Programming With ProDOS. It’s a very faithful colour scan, but at 170 MB for 280 pages, it’s a bit unwieldy. I suspect it’s Adobe Acrobat Paper Capture’s fault: while it makes turning scans into readable files really easy, it doesn’t warn against using 600 dpi full colour for a book with only decorative use of colour.

Good old Ghostscript saves the day, though:

gs -sDEVICE=pdfwrite -sColorConversionStrategy=Gray -dProcessColorModel=/DeviceGray -dPDFSETTINGS=/ebook -dNOPAUSE -dBATCH -dSAFER -q -sOutputFile=1983-A2L2013-m-a2-bpwp-grey.pdf -- 1983-A2L2013-m-a2-bpwp.pdf

By downsampling the scanned images and converting everything to greyscale, the result’s only 16 MB. All text and indexing from Acrobat is left intact.

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