Re: Determining the ideal resolution automatically?

Owen Ransen <willy@[EMAIL PROTECTED]
> wrote:

> On Wed, 30 Apr 2008 03:46:10 -0700 (PDT), Tim.Ahrens@[EMAIL PROTECTED]
 wrote:
> 
> >My question is: is there a tool that does this job automatically? I
> >mean, in a blurry image, determining what the "real" resolution is and
> >then downsample automatically? Sorry if this has been asked before, I
> >couldn't find anything.
> 
> Going highly technical but I suppose you'd need a program which
> did a 2D Fourier Tranform on the image to find out the highest
> spatial frequencies which exist in the image. That would tell 
> you the max sampling size you'd need in x and y axes, and hence
> the number of pixels in x and y.
> 
> Unfortunately it may go gah gah if you have dust or specks in
> the image, the FFT would not "know" you wanted to get rid of those.
> 
> I understand your reasoning because I've thought about this myself
> with a scanning application I am writing. Why store at 1200 DPI
> an image which is has exactly the same data at 200 DPI (scanned
> DPI I mean).
> 
> Exagerating a white piece of paper looks the same at 1 DPI as
> at 1000 DPI!
> 
> The FFT won't be in the first version though!

	Hmmm I don't think 1200-PPI vs 200-PPI is same or have anything to do
with
turning blurry 8MP image into sharp 2MP image without loss.  Or, most
people
would agree with you that it's kinda crazy for an average people to keep
the
1200-PPI when it may do just find or more than good enough at 200-PPI or
sometime even 150-PPI and depending on the image it may even be better
with
less than 100-PPI than more.

	Some people may even think it's crazy to scan at 1200-PPI to begin with.
And I hope you understand why in some case I agree smaller may be better,
while disagree in other case.  And that's why I never care to set my image
to 300-PPI or 150-PPI or why not enjoy the one more than 300-PPI or
increasing the PPI higher than its real value won't do no good.