[vox-tech] Changing the print resolution of JPEG images by script

[Ryan]

On Friday 08 April 2005 05:24 pm, Ken Herron kherron+lugod-at-fmailbox.com 
|lugod| wrote:
> Henry House wrote:
> > One of the more common operations that I need to do with JPEG images is
> > to change their print resolution so that when printed (e.g., as included
> > figures in a LaTeX document) they print at 300 dpi (for example) instead
> > of 72 dpi.
>
> To start with, DPI (dots per inch) implies that each pixel has a
> physical size, 1/72 of an inch or whatever. As far as I know, JPEG
> images have a size in pixels (e.g. 106 by 64 pixels for the watertower
> image on the LUGOD home page), but the pixels have no inherent physical
> size. Something outside of the image--probably the software used to
> embed the image into the document--is deciding how large the image
> should appear on the page. I would expect that you can adjust that, ie
> tell the software how large to print the image or what DPI to use.

JPEG files include DPI as metadata, which is used by some programs. I suspect 
it would be fairly trivial to write a program that changes this.

-- 
Ryan Castellucci - http://ryanc.org/
GPG Key: http://ryanc.org/files/publickey.asc