Hello Peter,

On Wednesday 07 January 2004 07:50, RJS wrote:

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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.

Yes, please. I sure that it's better/faster than my PIL or PythonMagick efforts. I don't know about machine vision etc, but shift is indispensable for video astronomy.

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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 operations.

Yes, it is straight-forward, in a way, but I'm always scouring the net for C and Python algorithms. Very (most?) often they're better than my own. This app is really a proof-of-concept; hopefully others will incorporate the "clipped image stacking" into their already fine astro apps. The problem is that the standard methods - median, mean, or summing - all suffer when long images in unequal exposure stacks have large clipped regions. Thanks, Ray http://rjs.org