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Subject:RE: graphics format From:Christine -dot- Anameier -at- seagate -dot- com To:"TECHWR-L" <techwr-l -at- lists -dot- raycomm -dot- com> Date:Tue, 6 Mar 2001 14:36:33 -0600
Melissa Akers quoted three bits of graphics advice she received:
<<Some versions of Acrobat actually condensed images, compressing them
during the PDF process, so GIFs, which are already compressed, come out
unreadable.>>
<<If size doesn't matter, I'd use .BMPs, especially if you are taking
screen
shots. BMP's screen shots look much clearer in my RoboHelp system ,than
JPEGs or GIFs.>>
<<.BMP format is the the lowest-quality format you can save a picture or
<<graphic in. If at all possible, save the file in .GIF or .JPG or .PNG
**BEFORE** you save it in .BMP format.>>
(1) All versions of Acrobat compress images by default. You have to go into
your Distiller job options and change compression to ZIP 8-bit, and turn
off downsampling/resampling. If you don't, *any* graphics in your PDF,
pre-compressed or not, are likely to get distorted. GIF is no worse than
other image format in PDF as long as you don't use transparent GIFs in your
documents.
(2) There is no reason BMPs should look clearer than GIFs. I would
absolutely avoid JPEGs for screen captures because the compression makes
the type in the screen captures blurry and distorted. But GIFs work fine.
(If you're having trouble getting GIFs to look right, you may be reducing
the color palette too far.) Also: size *always* matters for screen captures
in documentation, because large files are cumbersome to work with, take
longer to download and render, etc.
(3) Bitmap quality depends on the color palette--i.e., if someone saves a
BMP in Paint, they can save it as a 16-color BMP and the appearance will
deteriorate, or as a 24-bit bitmap that is pristine... albeit unnecessarily
large. In most cases you can convert that into a 256-color GIF with little
or no loss of quality. And again, whatever you do, do NOT save screen
captures in JPG. If you leave the JPG compression low enough (i.e., set the
quality at the top end of High), you may get away with it, but then you
lose most of the compression and defeat the purpose of using that format.
In WinHelp you're stuck with BMPs (256-color ones, IIRC) but for HTML, go
with one of the following:
* For photographs and other images with subtle gradations of color, try
JPGs. I would use JPGs for web-page interface elements like beveled or
drop-shadowed buttons. (If that's the sort of thing the artists are sending
you, perhaps they can work out the JPG compression issues themselves and
send you a JPG. They may have a better eye for the subtle differences in
quality, since it's their images they're looking at.)
* For screen captures, use GIFs. GIFs are also good for line art,
cartoon-like graphics, and other images that use a limited color palette.
IPCC 01, the IEEE International Professional Communication Conference,
October 24-27, 2001 at historic La Fonda in Santa Fe, New Mexico, USA.
CALL FOR PAPERS OPEN UNTIL MARCH 15. http://ieeepcs.org/2001/
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