Advice for compressing TIFFs

  • Thread starter Thread starter cubilcle281
  • Start date Start date
(rafe b was probably thinking as a user, not a programmer, though.)
Click to expand...

In that context, yes. A public (open) file spec is one thing,
and a very good thing indeed. But it's quite a different thing
to have lots of applications that properly support the spec.


rafe b
www.terrapinphoto.com
 
cubilcle281 said:
OK, so PNG might be a contender.

Next question then is how do I convert from TIFF to PNG?
I would like to automate this also. None of my software
does 16-bits/channel (remember, no Photoshop). Does
Image Magick support 16-bit/channel TIFFs and do TIFF
to PNG in 16 bits/channel?
Click to expand...

Yes, ImageMagick supports 16-bit/channel conversions. For that you'd
need the 16-b/ch precompiled binaries for your platform, or compile it
yourself from the source code, but then you'd also need the various
(file format) libraries.
I figure I can use my limited knowledge of Perl I can
produce a command stream, but from the documentation
I read on the site I couldn't tell whether 16-bits/channel was
supported.
Click to expand...

I don't recall your platform, but on a Windows command line use the
"Convert" command and create a copy in a different format, or you can
use the "Mogrify" command to replace the original (careful with that,
things can go wrong). If you use the Windows "For.. in .. do" command
you can cycle through all files in a folder and place the conversions
somewhere else.

Bart
 
Don said:
Unfortunately, J2K doesn't seem to have been adopted widely. It does
show up in various software but most people seem to continue with
plain-vanilla JPG.

Basically, as long as you keep the software which can convert J2K back
to some other format you should be "future proof".

One other thing. All compressed formats are much more susceptible to
data corruption! If a single bit fails in a compressed file some
programs may refuse to read the whole file or (if you're lucky) only
data following the failed bit. Either way, you will virtually lose the
image.

On the other hand, if you use an uncompressed format then lots of data
can fail and you can still recover the image, perhaps (conceptually)
treating failed bits as "digital dust" or "digital scratches".

So, considering all that and the constantly falling price of media I
don't think any compression is really worth the trouble for the
purpose of permanent archiving.

Don.
Click to expand...

Yes, I did consider keeping the software I used, but suppose I upgrade to CS3
and CS3 suddenly refuses to work with the fnord plugin... But I didn't know
about the vulnerability of compressed images as compared to uncompressed.

And I agree with you about cheaper media. I could burn uncompressed TIF to DVD,
though I manage to squeeze only 18 files with size 232 MB onto one disc, with
some PAR files to restore a few errors if needed. In my case I would need 85
DVDs to archive all my scans :) At the moment I have it all on 45, including
the JPGs as well as the J2Ks. I use the JPGs as a kind of index.

Greetings, Alex
 
The newer versions of Photoshop elements handle 16 bit/ color tiff and
png files just fine.
I did a test with converting a tiff to a 16/color png, the size of the
png was about 36% the size of the tiff. It surprised me that it would
be that much, this is a pretty clean image so that might help. I did
check and the full 16bits of data seems to all be there.

Scott
Click to expand...
I had thought you needed the full Photoshop to handle 16-bit/colour.
Do you know which versions of Elements can do this?

Regards
Ian
 
Ian said:
I had thought you needed the full Photoshop to handle 16-bit/colour.
Do you know which versions of Elements can do this?
Click to expand...

I have version 3 and it mostly handles 16bit/color images. There are
some limitations when working in 16 bits, the largest is you can't use
layers. I mostly scan in 16 bits/color bring the image into PSE3,
make the major level adjustments and then convert to 8 bits/color.

I mostly find that an 8 bit / color scan works as well as 16
bits/color, but I don't see a speed difference scanning at 16
bits/color so I just leave the scanner in this mode.

Scott
 
Yes, I did consider keeping the software I used, but suppose I upgrade to CS3
and CS3 suddenly refuses to work with the fnord plugin... But I didn't know
about the vulnerability of compressed images as compared to uncompressed.
Click to expand...

I still have PS6 and didn't bother upgrading because it does
everything I need. Mind you, I did write a couple of programs on the
side (to combine twin scans, for example).

The important thing, however, is not so much PS but software to
convert between different formats. PS does that but it's too big and
clumsy. Because of that (complex machines break more than simple
machines) it has a tendency to fall over or break other things, as
you've discovered.

You would be much better off saving a (relatively) simple program like
IrfanView which will do all the conversions and is not resource hungry
plus it's likely to work on at least a few of the future versions of
Windows (assuming you run Windows).
And I agree with you about cheaper media. I could burn uncompressed TIF to DVD,
though I manage to squeeze only 18 files with size 232 MB onto one disc, with
some PAR files to restore a few errors if needed. In my case I would need 85
DVDs to archive all my scans :) At the moment I have it all on 45, including
the JPGs as well as the J2Ks. I use the JPGs as a kind of index.
Click to expand...

So far I've burned about 55 and my projection is 100 DVDs exactly. But
that will contain everything: slides, negatives and photos. However,
since I scan slides twice (twin scans: once for highlights and once
for shadows) once I merge them I should be able to fit everything on
about 70 DVDs.

Finally, as the HD-DVD takes over in the next couple of years, those
100 DVDs will shrink down to about 10 HD-DVDs! By then it will be time
to "refresh" my backups anyway, so in about 3-4 years I expect I will
migrate all my archives to HD-DVD.

So, given all that, it really doesn't make much sense to archive
compressed files and have another thing (compression software) that
can go wrong in the future. By contrast, TIF is pretty straightforward
and will be supported. But even if it's not, it's very easy to write a
TIF reader/converter.

Don.
 
Hi all,

Just as a postscript to this conversation, I will tell you how it all
worked out.

I downloaded the 16-bit version of ImageMagick, and converted some
TIFFs to PNG. The size went down from 53MB to 43MB, enough to allow me
to fit 100 images onto a DVD, which is my intention.

The PNG files opened in PSE2 with strange colors, so I converted back
to TIFF to see if that fixed it...nope, colors were still wrong (we are
talking about psychidelic effects here!). I then noticed that the
re-converted tiff was also only 43MB. Some ImageMagick commands later
(can't remember which one, but it gives file info) I discovered that
the TIFF file had been compressed with ZIP compression (that is, a
ZIPped image in a TIFF, not a TIFF in a ZIP file). Imagemagick
supports this and a few other compression types, but ZIP compression
worked best for me (and yes, LZW took the filesize out to 64MB!).

So, I can compress the files, but PSE2 doesn't like them. If I could
live with an extra decompression step I could put the ImageMagick
binary on the DVD for extra safety (and JPEGs for backup).

Due to low disk space I used the 'mogify' command instead of 'convert'.
After 40 images I ran out of Disk cache (so ImageMagick tells me) and
the last 10 files of the back were destroyed. So, I have to re-scan
these images (which means re-borrowing them). This one is my own
stupid fault, but I now trust ImageMagick a little less.

All-in-all, the lack of support for compressed TIFFs makes me nervous
about using them for archival purposes. Therefore, I have decided to
go with 75 images per DVD, even though it complicates my own processes.

Thanks all for your help!

C
 
Did you try just converting the tiffs to png via Photoshop? This works
for me, no strange color shifts, and reconversion to tiff arrives at
same starting point, ie: no hiistogram change, file size the same. I
got similar compression as yours (around 25% reduction) going to png,
but am thinking to stick with uncompressed tiffs for my pending burns.
I'm rapidly running out of hard drive space so this is on my mind.

FWIW, with my uncompressed tiffs, I'll be getting 20 on a dvd.
 
That would be OK, only I am using PSE2, which would only convert at 8
bits/channel. Since this is archival I would prefer 16 bits/channel.

As for hard drive space, I know how you feel - 200GB, 88MB free (which
Windows continuously reminds me of!). Most of it is AVI files from my
DV camera, awaiting conversion and buring to DVD.

C
 
The TIFF standard supports this, but not many TIFF readers and writers. IMO,
best stay away from 'true' 12 bit or other exotic TIFFs, like TIFFs with jpeg
compression.

-- Hans
 
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