# [Numpy-discussion] iterate along a ray: linear algebra?

David Huard david.huard at gmail.com
Mon Jul 3 08:19:07 CDT 2006

```Hi Stephen,

I don't know much about image analysis, but in the scipy tutorial
(7.2Filtering), there is an example of an image filter that highlights
the edges
of an image. If I guess correctly, it finds the smoothing spline of the
image and then computes the derivative of the spline. A high derivative
means that the image intensity shifts rapidly, so maybe that could help you.

David

2006/6/30, stephen emslie <stephenemslie at gmail.com>:
>
> I am in the process of implementing an image processing algorithm that
> requires following rays extending outwards from a starting point and
> calculating the intensity derivative at each point. The idea is to find the
> point where the difference in intensity goes beyond a particular threshold.
>
> Specifically I'm examining an image of an eye to find the pupil, and the
> edge of the pupil is a sharp change in intensity.
>
> How does one iterate along a line in a 2d matrix, and is there a better
> way to do this? Is this a problem that linear algebra can help with?
>
> Thanks
> Stephen Emslie
>
> Using Tomcat but need to do more? Need to support web services, security?
> Get stuff done quickly with pre-integrated technology to make your job
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