RE: [APML] Off Topic: Histogram Help

["Richard Klappal" <klappal@xnet.com>]

In Photoshop 5.0.2 (Other versions may have moved the menu items),
	select IMAGE > Histogram...
	Place cursor on the histogram display.
	Lower right item in text:numerics in the histogram display is PERCENTILE.

Percentile is % of the image that is darker, or equal, to the value
specified by the cursor's position

Other values in the box (count, pixels, level, ...) give, and allow
calculation of other relevent values:
	100% * count/pixels gives % of the image that is at that particular level,
...


Rich

-----Original Message-----
From: owner-astro-photo@seds.org [mailto:owner-astro-photo@seds.org]On
Behalf Of Joseph Celmer
Sent: Wednesday, February 20, 2002 22:24
To: astro-photo@seds.org
Subject: Re: [APML] Off Topic: Histogram Help


Shekhar,

Yes, I can convert the image to a binary, which I believe makes all the
pixels
either black or white. In Picture Window, I get the two spikes you refer to,
but
as far as I know, no numerical values are assigned. If Photoshop does
display a
readout of the number of pixels represented in the spikes, that's what I'm
looking
for.

Could I email a sample image to you and have you give it a try? (tomorrow)

Thanks,
Joe



Shekhar Borde wrote:

> Are all the pixels black or white?  ie., there are no intermediate
grayscale
> values?  If that is true then the histogram in PS should have only two
spikes,
> one at each end of the scale (0 and 255).  Just move your cursor over each
> spike and you should get the readout for the number of black and white
> pixels respectively.
>
> But if you have a grayscale image spanning multiple values in the 0..255
> range then I don't know of a quick or easy way to do it.  Maybe someone
> else might have a better idea.
>
> Shekhar
>
> ----- Original Message -----
> From: "Joseph Celmer" <celstar@frontiernet.net>
> To: "Post Astro-Photo Message" <astro-photo@seds.org>
> Sent: Wednesday, February 20, 2002 5:26 PM
> Subject: [APML] Off Topic: Histogram Help
>
> > Dear APML,
> >
> > I have an image which consists of a smattering of black dots of various
> > sizes and shapes on a white background. I am interested in determining
> > the relative % surface area of the black or white to the total area. Is
> > Photoshop or any of the common software capable of expressing this
> > relation in a quantifiable histogram or other manner ( black versus
> > white pixel count perhaps?)
> >
> > Thanks !
> > --
> >
> > Joe Celmer
> > celstar@frontiernet.net
> > http://www.frontiernet.net/~celstar
> >
> >
> >
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--

Clear Skies!

Joe Celmer
celstar@frontiernet.net
http://www.frontiernet.net/~celstar



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