15 Aug
2006
15 Aug
'06
9:24 a.m.
Armistead, Jason wrote:
My $0.02 worth on the abovementioned subject:
TIFF has lots of ways data can be encoded within the basic TIFF file
structure, including LZW, CCITT G3 and CCITT G4 formats. If anyone is
interested, get a good look at the TIFF V6 specification, although the links
on the www.libtiff.org site seem to be broken and Adobe has now put their
copy of the TIFF specification behind a whole lot of "developer registration
required" pages you need to get through first.
See also http://www.awaresystems.be/imaging/tiff/tifftags/compression.html
which describes the TIFF tags relating to compression of image data.
I've had good results with TIFF in documents that I have prepared
(user manuals, etc.). *But*, you can't stray too far from what
is "expected". E.g., don't use weird BITS_PER_PIXEL values
and expect many decoders to be able to handle your files! :-(
Also, I have found that many *encoders* fail to sort the tags
properly so when designing decoders, *expect* this problem :-/
From where I sit, we've used TIFF with CCITT G42D
(fax) compression on
bitonal (black and white only) image documents for 150,000 engineering
drawings with excellent results. This is a totally lossless compression
format (what you get back is exactly what you put in) specifically designed
to do a good job with what you'd find on pages of drawings or of text. If
you don't need colour or greyscale, then CCITT G42D is hard to beat.
Within the US military, the CALS (Computer-aided Acquisition and Logistics
Support) Type 1 specification for bitonal images basically wraps the
compressed CCITT G42D data inside a slightly different wrapper to TIFF -
CALS is a fixed length text header, and TIFF is a lot of binary stuff. It's
easy to convert between the two formats when you know how.
What I like about TIFF coupled with CCITT G42D compression most is (a) it's
lossless, (b) supports multi-page documents, (c) it's an open specification
with (d) an open source library to manipulate the files (LIBTIFF) and (e) it
is widely supported with hundreds of viewers available (on Windows, the free
Imaging component works fine for most people). I can also easily transform
my TIFF data into Postscript (btw Level 2 Postscript more or less supports
CCITT G42D compression too), PCL or even into PDF with not too much drama.
In comparison, PDF is locked in more or less to Adobe's Acrobat Reader (yes,
I know there's always Ghostscript / GSView and friends ! ), and not as easy
to manipulate - I call it more of a nearly "final form" document format than
TIFF.
I thought PDF's could just be used to *encapsulate* regular TIFF's?
I.e., in much the same way that they can encapsulate JPEGs, etc.
JPEG is not suitable because it was a lossy format
targeted at colour images
more than black and white, and it wasn't multi-page. I believe the JPEG
2000 specification has improved on some of these such as providing a
lossless compression option, and can handle multi pages. I don't know if
software to support all these features is (a) cheap or (b) available.
For my money, I'm sticking with TIFF
Agreed.