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[tlug] Any graphics experts here?

I am trying to print some sheet music using an online printing service (laser A3 output, stapled in a proper "book"); I assembled a PDF file containing the 12 pages and sent it, to receive an error message complaining that it is not 'greyscale'...



Well, of course in "reality" (if such exists) there are only black and white bits, and I don't know much about PDF, but all that should be necessary to change is for any colour value to be moved to its closest (by any standard) point on the r=b=g line. I have given a ("black-n-white") PDF file to our local printers for a poster, and they have no difficulty at all in printing it in black and white.

All searches seem to lead to Imagemagick, which isn't really the job, because it does everything by resampling, resulting in terrible quality. But even so, it is not clear what it means for a pdf to be "grayscale"... see following thread:

This says that even if you convert the colorspace value in the PDF to "gray(scale)", you will see sRGB given as the "colorspace", because Imagemagick always creates 3D colour. Worse, I found authoritative comments suggesting that in fact *objects* within a PDF have colorspaces, but the PDF file itself does not. So I don't really see how I could even tell if their printing system is going to believe it is a monochrome file anyway. FWIW, here are the "help" pages, which presumably might do something if I were using either of these bits of software:

Sorry, this is a bit rambling. I don't quite where to go next...
Brian Chandler

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