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MathGroup Archive 2007

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Re: Bitmap data extraction (matrix of matrix)

  • To: mathgroup at smc.vnet.net
  • Subject: [mg76463] Re: Bitmap data extraction (matrix of matrix)
  • From: Albert <awnl at arcor.net>
  • Date: Wed, 23 May 2007 05:02:24 -0400 (EDT)
  • References: <f2u51n$k09$1@smc.vnet.net>

mkorneck at nd.edu wrote:
> Hello,
> 
> This is most likely a simple question for those who use Mathematica on
> a semi-regular basis, but ...
> 
> I have a 512x512 matrix composed of 1x3 matrix elements, and want to
> create a 512x512 matrix composed of a single value in the original 1x3
> elements.
> 
> That doesn't look very well defined, so please let me explain further
> in the hopes of clarifying what I am after.
> 
> It's a bitmap image file (512x512) and I want to extract a part of the
> "raw" data for further processing. The raw data in the original file
> consists of values for the red, green and blue (RGB). I would like to
> create a matrix composed of only the *red* values across the 512x512
> array.
> 
> As a simplified example ....
> 
> Given RGB = {{1,0,1},{2,3,2},{4,6,4},{3,2,1}}
>                     {{9,1,3},{3,2,1},{4,3,3},{5,3,2}}
> 
> 
> I would like to end up with R = {1,2,4,3}
>                                             {9,3,4,5}
> 
> Thank you for your time,
ist this what you are after?

In[27]:=
data=Table[Random[],{512},{512},{3}];
In[28]:=
Dimensions[data]
Out[28]=
{512,512,3}
In[30]:=
datared=data\[LeftDoubleBracket]All,All,1\[RightDoubleBracket];
In[31]:=
Dimensions[datared]
Out[31]=
{512,512}

hth,

albert


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