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Re: non rectangular crop

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  • Subject: [mg110736] Re: non rectangular crop
  • From: David Bailey <dave at>
  • Date: Sun, 4 Jul 2010 03:08:45 -0400 (EDT)
  • References: <i0n9tr$hs4$>

On 03/07/10 13:20, Patrick Scheibe wrote:
> Hi,
>> is it possible to have a not rectangular image in Mathematica?
> no. You can of course use SparseArray to create one and therefore you
> could create an image where you don't have to specify the whole image
> matrix
> Image[SparseArray[{{1, 1} ->  0.3, {7, 2} ->  0.5, {9, 9} ->  1}, {10,
>     10}]]
> but internally it stores the whole matrix
> InputForm[%]
>> I have a lot of images acquired by microscope - they are all squared,
>> with the circular field of view surrounded by black.
>> I'd like - for further processing - to crop all the black region
>> outside the circle.
> but if the outside of your circular region is black then it is already
> croped in some way because filters like binarization, blur-filters,
> segmentation, registration, ... will ignore the black regions. I don't
> see your concerns.
> Cheers
> Patrick
Of course, you can fill the black part of your image with a totally 
transparent 'colour' using the 4-argument form of RGBColor. That will 
mean that you can place the image over other graphics, and only the 
circular region will obscure what is underneath.

David Bailey

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