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Re: importing image and getting numbers from the gray intensity

  • To: mathgroup at smc.vnet.net
  • Subject: [mg49406] Re: importing image and getting numbers from the gray intensity
  • From: sean_incali at yahoo.com (sean kim)
  • Date: Sat, 17 Jul 2004 06:40:12 -0400 (EDT)
  • References: <cd5okp$b2c$1@smc.vnet.net> <cd8b5g$olp$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Hi Paul, 

Thanks for the reply, 

I can't seem to get this to work. 

I copied, pasted, converted and renamed it to pixel. 

but when i go...

In[74]:=
pixels=First[
      Cases[pixels,RasterArray[x__]:>x,Infinity]]/.RGBColor[r_,g_,
        b_]:>(r+g+b)/3

From In[74]:=
First::first: {} has a length of zero and no first element.

Out[73]= 
First[{}]

Thanks for any thoughts in advance 

sean 



Paul Abbott <paul at physics.uwa.edu.au> wrote in message news:<cd8b5g$olp$1 at smc.vnet.net>...
> In article <cd5okp$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


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