[XeTeX] XeLaTeX resolution

[jan ziebiker]

well, it's not that straightforward. first, it would be more appropriate 
to use ppi (pixels per inch) when talking about resolution of digital 
images or screens, and use dpi (dots per inch) when talking about 
resolution of output devices like printers.
second, what is the right resolution? it can't be said in general and 
severeal things should be considered when determining the right 
resolution: printing technology, desired quality, the distance from 
which the image will be looked at, and possibly some other. in short, 
the purpose of the image (printing, part of a web page...) should decide.
there is, however, one general "rule": the longer the observational 
distance and the lesser quality demands, the lower can be the resolution 
and the smaller the size of the image-file, and vice versa. anyhow, 
there is practically no use in having resolution higher than 300 ppi, 
since human eye is unable to distinguish so small "points".
the recommended value of 300 ppi fits quite well for "older" printing 
(assuming the observational distance about 25 cm) technologies that use 
conventional rasters and for high-quality output, but here not only 
resolution plays its part. modern digitas printers can print even 
"low-resolution" images quite well; you can make a test to see what 
results a 200 ppi image and the same image at 300 ppi give.
ias I said earlier, the decision about resolution can't be 
straightforward and it would be probably made easier if one knew how a 
printer handles pixels of the digital images, i.e. what kind of 
correspondence is between pixels (of an image) and dots (produced by a 
printer; but for modern digital printing the term "dot" is very very 
vague, I am afraid)

that's it.
jan

Meho R. napsal(a):
 > I read somewhere that resolution of 267 dpi for bitmap images is 
enough. Can anyone confirm it?
 >
 > ----- Original Message -----
 > From: "Jonathan Kew" <jonathan at jfkew.plus.com>
 > To: "Unicode-based TeX for Mac OS X and other platforms" <xetex at tug.org>
 > Sent: Monday, February 23, 2009 10:17:19 PM GMT +01:00 Amsterdam / 
Berlin / Bern / Rome / Stockholm / Vienna
 > Subject: Re: [XeTeX] XeLaTeX resolution
 >
 > On 23 Feb 2009, at 20:24, Nicolas Vaughan wrote:
 >
 >> Hi Mike,
 >> Thanks for your reply.
 >> So I shall not worry about my publisher's requirement if I use OTF?
 >
 > For fonts (if you use TrueType or OpenType fonts) it certainly 
shouldn't be an issue. Outline fonts like this are effectively 
"infinite resolution".
 >
 > I think the concern is with included images. If these are vector 
graphics, no problem; but if they're bitmapped images (such as scanned 
photos or line-art) then resolution is an issue. But AFAIK, xetex/ 
xdvipdfmx won't change them, it will just include the image data as 
provided, with appropriate positioning and scaling. So you just need  to 
make sure your original PNG or JPG images are sufficiently high 
resolution (allowing for scaling, if you're not placing them at their 
original full size) to meet the publisher's requirements.
 >
 > 1200dpi would be appropriate for line art; for scanned color photos, 
  you shouldn't need anywhere near as high dpi because of the screening 
  processes involved.
 >
 > JK
 >
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