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Re: masked arrays and nd_image: msg#00023

python.numeric.general

Subject: Re: masked arrays and nd_image

> I did not write nd_image with masked arrays in mind, I imagine it won't
> work for most functions. I am not planning to support masked arrays

Yes, I expected this. I knew I was pretending too much ;o)

One can always try :-)

> . If you just want to mask out some of the results, apply the mask
> afterwards. If you actually want to deal with masked values in the
> convolution itself, you are out of luck with the convolve1d function,
> it does not support that. In that case you could try to write your own,
> using the generic filter functions (see the manual).

Ok, this would imply writing a function with prototype FilterFunction1D, right? And the mask argument should be packed with the data or is there a way (which I don't see) to pass arguments to the filter other than the input image. Sorry if I'm annoying ;o)

If you do it in python, you feed generic_filter1d a function, if you make that a method of an object, your mask can be accessed as a attribute of your object.

If you want to do it in C, you can pass a CObject that holds the function pointer to a callback function with prototype FilterFunction1D. Additionally you can set the description pointer of the same CObject to an arbitrary pointer, which is passed at every call to the callback function. You can use that to store additional information for you filter, such as the mask. See the example in the manual which is written for the shift function, but the principle is the same.

Cheers, Peter



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