Re: importing image and getting numbers from the gray intensity

• To: mathgroup at smc.vnet.net
• Subject: [mg49371] Re: importing image and getting numbers from the gray intensity
• From: Paul Abbott <paul at physics.uwa.edu.au>
• Date: Fri, 16 Jul 2004 06:07:05 -0400 (EDT)
• Organization: The University of Western Australia
• References: <cd5okp\$b2c\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```In article <cd5okp\$b2c\$1 at smc.vnet.net>,
sean_incali at yahoo.com (sean kim) wrote:

> let's say you have an image of gray bands of varying intensity.
>
> such as the one seen on the website,
>
> http://encyclopedia.thefreedictionary.com/SDS-PAGE
>
> Is there anyway to change the picture or do something and be able to
> get numerical values for those bands?
>
> maybe define a vertical line and then go to the center of the each
> bands and measure how intense the gray is.
>
> or maybe define a rectangle and get the gray intensity in that...
>
> is there a packages or codes for doing that?  NIH image program which
> is freely avaialble can do this. But I wanted to do it in Mathematica.

There are several ways to do this. One way is to copy the image, paste
it into a Mathematica Notebook and then use

Cell | Convert To | InputForm

This will give you an input cell that includes a RasterArray of
RGBColors. Call this cell pixels, say, and enter it. You can then access
the pixels as follows:

pixels = First[Cases[pixels, RasterArray[x__] :> x, Infinity]] /.
RGBColor[r_, g_, b_] :> (r + g + b)/3

You can re-draw the picture as follows:

ListDensityPlot[pixels, Mesh -> False];

and do any other manipulation you want on the pixels.

Cheers,
Paul

--
Paul Abbott                                   Phone: +61 8 9380 2734
School of Physics, M013                         Fax: +61 8 9380 1014
The University of Western Australia      (CRICOS Provider No 00126G)
35 Stirling Highway
Crawley WA 6009                      mailto:paul at physics.uwa.edu.au
AUSTRALIA                            http://physics.uwa.edu.au/~paul

```

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