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MathGroup Archive 2004

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Re: importing image and getting numbers from the gray intensity

  • To: mathgroup at smc.vnet.net
  • Subject: [mg49427] Re: importing image and getting numbers from the gray intensity
  • From: Paul Abbott <paul at physics.uwa.edu.au>
  • Date: Mon, 19 Jul 2004 07:46:19 -0400 (EDT)
  • Organization: The University of Western Australia
  • References: <cd5okp$b2c$1@smc.vnet.net> <cd8b5g$olp$1@smc.vnet.net> <cdb1pf$aka$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

In article <cdb1pf$aka$1 at smc.vnet.net>,
 sean_incali at yahoo.com (sean kim) wrote:

> I can't seem to get this to work. 
> 
> I copied, pasted, converted and renamed it to pixel. 

pixel or pixels? 

Did the renamed cell, look like

  pixels = Show[Graphics[
   {AbsoluteThickness[1],GrayLevel[1],
   Polygon[{{4, 4},{148, 4},{148, 307},{4, 307},{4, 4}}],
   RasterArray[{{
      RGBColor[0.980392, 0.968627, 1],
      ... 
      }},
   {{4, 4}, {148, 307}}]}], 
   AspectRatio->2.10417,
   PlotRange->{{4, 148}, {4, 307}},
   ImageSize->{144, 303}]

or did it have Raster instead (this may be version dependent)?

> 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.

This would happen if you named it pixel instead of pixels, or if you get 
a Raster object instead of a RasterArray.

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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