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Re: importing image and getting numbers from the gray intensity


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

-- 
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