# Convolution using narray

**URL:** <https://rubytalk.org/t/convolution-using-narray/15029>\
**Category:** ruby-talk\
**Created:** [28 November 2004 23:35 UTC](https://rubytalk.org/t/convolution-using-narray/15029 "2004-11-28T23:35:17Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Brian\_SchrA\_der](https://avatars.discourse-cdn.com/v4/letter/b/c67d28/32.png) [@Brian\_SchrA\_der](https://rubytalk.org/u/Brian_SchrA_der)\
**Post date:** [28 November 2004 23:35 UTC](https://rubytalk.org/t/convolution-using-narray/15029/1 "2004-11-28T23:35:17Z")

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The narray documentation is a bit thin, so I'm asking here. I do want to do a convolution. Map a two dimensional kernel onto a two dimensional image. I thought the

FFTW.convol(a, b)

function of narray would do this. But I see that it requests to narrays of the same size? So I this can't be convolution. What is it, and where can I find a convolution function?

Regards,

Brian

> **···**
>
> --  
> Brian Schröder  
> [http://www.brian-schroeder.de/](http://www.brian-schroeder.de/)

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<div class="post-metadata">

**Author:** ![Brian\_SchrA\_der](https://avatars.discourse-cdn.com/v4/letter/b/c67d28/32.png) [@Brian\_SchrA\_der](https://rubytalk.org/u/Brian_SchrA_der)\
**Post date:** [29 November 2004 00:00 UTC](https://rubytalk.org/t/convolution-using-narray/15029/2 "2004-11-29T00:00:31Z")

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I promise to buy myself a good math book and get some sleep. I have to extend the kernel with zeros to the size of the image. I apologies. It is a long time since I have learned those things.

Regards,

Brian

> **···**
>
> On Mon, 29 Nov 2004 08:35:17 +0900 Brian Schröder \<ruby@brian-schroeder.de\> wrote:
> 
> > The narray documentation is a bit thin, so I'm asking here. I do want to do a convolution. Map a two dimensional kernel onto a two dimensional image. I thought the
> > 
> > FFTW.convol(a, b)
> > 
> > function of narray would do this. But I see that it requests to narrays of the same size? So I this can't be convolution. What is it, and where can I find a convolution function?
> 
> --  
> Brian Schröder  
> [http://www.brian-schroeder.de/](http://www.brian-schroeder.de/)