Re: PDFs--how big can you go?

Subject: Re: PDFs--how big can you go?
From: Graham Dowden <Graham -dot- Dowden -at- NMS -dot- OTC -dot- COM -dot- AU>
Date: Wed, 8 Oct 1997 08:55:02 +1000

Hillary Jones wrote:
> Does anyone know of a sort of formula you could use to figure out how
> much memory the resulting PDF file will be?

This is not possible because compression depends on the nature of the
source material, and pure text, vector art, bitmaps and multiple fonts will
compress to different degrees. For one type of material you could easily
generate an empirical formula by creating PDF files from one standard page
of source copied multiple times.

The PDF FAQ indicates that PDF may be larger or smaller than the source.
To summarise:

1 Why PDF is usually smaller than the original PS file
* Bitmaps downsampled
* PDF images are usually compressed
* PDF supports PostScript 2 compression
* PDF body text is usually compressed
* Optimized PostScript
* Reduced PostScript operators

2 Why PDF might be *larger* than original PostScript
* Inappropriate image compression
* PostScript loop unwinding
* Font embedding

Graham Dowden, dowdeng -at- nms -dot- otc -dot- com -dot- au
Telstra, 363 Oxford St, Paddington NSW 2021 AUSTRALIA

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