[Numpy-discussion] Update for IM. a small image processing system
verveer at embl-heidelberg.de
Wed Jan 7 04:45:01 CST 2004
On Wednesday 07 January 2004 07:50, RJS wrote:
> > I have uploaded a new version of my small image processing system IM to
> > "http://members.tripod.com/~edcjones/IM-01.01.04.tar.gz". Most of the
> > code in IM (pronounced "I'm") is inferior to "nd_image" so I will
> > eventually convert it all to "nd_image".
> > nd_image is however also still being developed and I am looking for
> directions to
> > further work on. I wondered if there is anything you would like to see
> in there?
> I have been working with Pythonmagic and numarray for a particular
> astronomy project/technique, and IM has a few things I might use; nd_image
> also has some interesting functions as well.
> I want to align and specially stack 8-bit grayscale images from a FITS
> cube, or BMP set, currently. So, my suggestions (hint, hint) are:
> 1. A method to shift an array to efficiently give the best alignment with
> another. My brute force shifting and subtracting from the main image is
> slow... Most programs I have seen align a selected sub-image, then shift
> the whole image/array (without rotation, although that would be desirable)
If I understand you well, you essentially want to estimate a shift between two
images. I have some code that can do that. I do not intend to include that in
nd_image for now, but I can send you the code.
> My _main_ objective is to stack progressively-longer-exposure 8-bit images
> into 16-bits, with the clipped pixels of longer exposures ignored in the
> summing process. The value of each pixel must be weighted inversely
> proportionately to it's exposure length (so shorter exposures "fill in" the
> clipped areas of the long exposures).
> 2. A fast method(ology) to do weighted sums of 2D arrays with a mask
> available for each array.
I think this can be achieved relatively easily with standard numarray
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