I frequently run into this. The photoshop default is 72 dpi, but the
printer uses 300 (or often higher depending on quality settings) so you
end up with something you thought should be an 8x10 printing out at
2"x3", or coming out all aliased...
In any case if there is a solution to this I would be happy to know
about it.
- Justin
Christopher Conroy wrote:
Problem is DPI is Dots Per Inch, not Pixels Per Inch. DOTS represent
an amount of ink, not an amount of pixels AFAIK. I do imagine that
there exists a linear or otherwise simple function that maps the DPI
of any printer to PPI, but I don't think it is universal. Figuring out
this relation involves inaccurate hand measurements and trial and
error. It's not /that/ bad however, and I'll probably end up having to
do just that.
But, if a nicer solution exists, I'd be happy.
On Tue, Mar 4, 2008 at 4:01 PM, Rob Sherwood <[EMAIL PROTECTED]
<mailto:[EMAIL PROTECTED]>> wrote:
On Tue, Mar 04, 2008 at 03:50:30PM -0500, Christopher Conroy wrote:
> Hey guys. This is a bit of an off the wall question, and my
google-fu hasn't
> really produced any answers to my liking.
>
> I would like to be able to calculate what size of an image to
produce in
> order to print to a target size. Specifically, I'm going to be
working on
> some CAD like stuff which requires a fair amount of computation.
Thus, I
> need to do all the computational geometry outside of any program
that
> supports such a feature (e.g. AutoCAD). I haven't started coding
any of
> this, though I will probably use Ruby or Java if that makes a
difference.
> Either way, I'll be creating images from the calculations.
>
> So, really this is just a matter of figuring out the best way to
map image
> resolution in pixels to print dimensions in inches.
>
> Anyone know of an easy way to do this aside from trial and error
testing?
> I'd like to be as exact as possible, and ideally not have to do
any image
> scaling at print time. (Ideally, the solution will work across
multiple
> printers. Bonus points for anything OS agnostic.)
Sounds like you need to know the dots per inch (DPI) of what your
printing technique is. A lot of printers use 300 DPI, so if you
want a
12" image, use 12*300 == 3600 pixels. Maybe you're asking
something more
complicated and I'm not understanding, but...
- Rob
.
--
Christopher Conroy
