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Subject:Re: Which image format From:"Chuck Martin" <cm -at- writeforyou -dot- com> To:techwr-l Date:Thu, 4 Mar 2004 14:31:21 -0800
"Wade Courtney" <courtney -at- hsq -dot- com> wrote in message news:231093 -at- techwr-l -dot- -dot- -dot-
> For those of you who have actual printed manuals that you have
> professionally printed, which image format do you use for your screen
> captures. I was using GIF, but my boss thinks they will look crappy in
> a printed manual, so he wants them all to be in png or vector art
> format. The vector art format is not a problem since there is very
> little vector art in my manuals, but I have hundreds of GIFS. I
> understand that PNG is better, but does it make that much of a
> difference in a professionally printed manual.
The first thought out of my brain (which doesn't take into account the
politics of the situation and is usually blunt, rather than diplomatic) is:
You boss is a graphics design expert?
Well I seriously doubt it because you report he/she "thinks" GIF files will
look crappy and suggests PNG as an alternative.
I'm not sure I really want to go into the differences between bitmapped and
vector graphics, the difference between lossless and lossy compression
techniques, and the effects of resolution (of both the source material and
the output mechanism) on appearance.
But I'll tick off a few bullet points:
- TIFF, BMP, GIF, JPG and PNG are a few of the most popular bitmapped
- Bitmapped formats are appropriate for screen captures, vector formats are
appropriate for drawings
- TIFF and BMP files are not compressed. TIFF has a greater color depth,
thus a larger file size.
- GIF, JPG, and PNG files are compressed formats.
- GIF compression is lossless: no information is lost when compressing.
- JPG and PNG lose image information when the file is compressed,
information that can never be recovered.
- GIF files can have a maximum of 256 colors (8-bits)
- Bitmapped files do not resize well, regardless of format.
- You can minimize the effects of distortion when resizing bitmapped files
by resizing them to a multiple of their original size: 0.25x, 0.5x, 2x, etc.
- The resolution of a screen capture (screens are typically 72dpi or 90dpi)
is not an even multiple of most output devices (300dpi, 600 dpi, 1200dpi,
- Converting a bitmapped image to a vector format will not result in a
- For screen captures, while most video cards are capable of displaying at
least 24-bit color, application interfaces typically use colors from an
8-but (256 color) palette.
- If you capture a screen from such an application and save it as BMP or
TIFF, you're saving 8-bits of color information in a 24-bit format,
needlessly inflating file size.
- PNG is not "better" than GIF; PNG captures more colors, but at the cost of
losing image data.
Way back when I was working for a company that send PostScript output (from
FrameMaker) to a printer to print bound books. I forget the format we saved
all of screen captures in (many were on a Mac), but some of them were BMP.
We had some issues once with how the graphics turned out, and we ended up
tweaking a couple of settings (it may have been the resolution of the file
somehow) and the printed manual looked fine.
Remember, though, screen captures are used mostly for users to make sure
they are in the right place. Readers rarely, if ever, actually "read" the
screen capture to see what data to enter or what choices to make.
So here's a question: have you and your boss *seen* a finished book from
what you're producing? If so, is the qraphics quality poor? And if so, have
you discussed this with your printer (they are the professionals on the
subject after all) to work out a resolution? If not, can you talk to your
printer and ask if what you're doing will provide clean, crisp output?
Better yet, can you sent your printer a sample file and get a blueline back
to get an idea of the output quality? (I realize bluelines aren't top
For me, I save screen captures in GIF format. I also resize them, typically
User Assistance & Experience Engineer
twriter "at" sonic "dot" net www.writeforyou.com
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