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Re: useful toolfunction

  • To: mathgroup at smc.vnet.net
  • Subject: [mg130317] Re: useful toolfunction
  • From: Matthias Odisio <matthias at wolfram.com>
  • Date: Tue, 2 Apr 2013 03:29:49 -0400 (EDT)
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Dear Robert,

On 3/28/13 10:54 AM, roby wrote:
> Dear Mathematica user
> 
> sometimes it would be helpful to use the coordinate picker tool
> of the 2D Drawing toolbox to be able to extract a subimage of an
> image displayed in the frontend.
> 
> The problem here ist that the picker tool gives you x,y coordinates
> with y positive direction growing from bottom to top.
> Whereas ImageTake first needs row indices growing top to bottom
> followed by column indices.
> 
> The following function provides most of what is needed:
> 
> 
> 
> ImageTaker[img_, c_] := 
>  ImageTake[img, Sequence @@ ({First@ImageDimensions@img, 0} +
>      (c // Transpose // Sort /@ # & // MapAt[-Reverse@# &, #, 2] & // 
>        Reverse))]
> 
> 
> 
> ImageTaker accepts 2 paramters the first one is the source image, the second
> is the x,y coordinate pair specifying the subimage.
> 
> So the procedure is the following:
> pick twice inside the source image using the coordinate picker tool,
> copy the coordinates by pressing CTRL-C,
> paste the coordinates CTRL-V to the function above as second parameter,
> feed the source imgage as first parameter e.g.
> by referencing an output cell containing the image
> by %nnn and evaluate it.
> 
> this gives you something like this:
> 
> ImageTaker[%nnn,{{x1,y1},{x2,y2}}]
> 
> which will evaluate and display the desired subimage.
> 
> Robert
> 

Did you have a look at ImageTrim? It should help.

Matthias Odisio
Wolfram Research






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