[OSM-talk] will walkingpapers printed on black and white work?

Richard Fairhurst richard at systemed.net
Sat Feb 27 10:56:46 GMT 2010


Tom Hughes wrote:
> The PDF that a scanner produces will normally just contain a 
> big embedded bitmap image. No idea how easy that is to 
> extract though.

Some scanner software produces a composite PDF with both vector content
(OCRed text) and the bitmap image in front. The vector content is invisible
- not sure whether this is done by layering, or some special PDF
instruction, or whatever. Regardless, the effect is that the document looks
as the original, but you can copy and paste the text.

GhostScript will rasterise any PDF easily:

    gs -sDEVICE=jpeg -sOutputFile=output.jpg -dBATCH -dNOPAUSE -dSAFER
input.pdf

cheers
Richard
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