Question about PDF manipulation

[Paul Koning]

>>>>> "Jules" == Jules Richardson <julesrichardsonuk at yahoo.co.uk> writes:

 Jules> Looking at the PDF file, I'm not convinced there's any TIFF
 Jules> data in there to be honest. It looks more like the image is
 Jules> re-encoded from the input TIFF to PDFs own way of storing
 Jules> bitmap data - in other words it's not simply a wrapper for a
 Jules> bunch of TIFF images, but merely a wrapper for bitmap data in
 Jules> PDF's own format. That's something of a disappointment; I
 Jules> always thought PDF just encapsulated the input images rather
 Jules> than re-encoding in any way...

Makes sense.

The purpose of PDF is to distribute final form documents, for viewing
and for printing, including commercial printing.  So it's like
PostScript, but more rigorously defined, and compressed for space
efficiency.  A PostScript file produced from an image has the pixels,
so they can be printed (in the original colorspace, unless your
document manipulation program converted it, as some do or can be told
to).  Given the purpose of these file formats, there's no reason for
it to preserve the TIFF metadata, nor the TIFF format, since the
intent is to accurately put pixels on screen or paper.

The encoding will be lossless, though (at least normally -- I think
you can tell Distiller to use JPG style compression but sensible
people know better than that).  So when you export the image from the
PDF, you get the original pixels back.

For purposes of scanned document archives, that is what you need,
which is why PDF is fine there.

       paul