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T.A. McGlynn (NASA/GSFC)
Flux-conserving resampling techniques have typically been both complex and slow. This paper describes a simple and relatively fast flux-conserving resampling technique based upon Sutherland-Hodgeman clipping. The algorithm essentially considers each original image pixel as a clipping window that clips the resampling pixels. The algorithm is exact except for the approximation that the boundaries of an individual pixel are considered to be straight lines in the plane of the image.
The algorithm easily accommodates the situation where there is a dead space between pixels or equivalently the drizzle technique of Fruchter and Hook where the flux of a given pixel is nominally restricted to an inner region to help preserve resolution during the resampling. For images of an intensive quantity such as temperature, the technique can be adapted get exact averages for resampling pixels. The resampling can be done either by projecting the resampling pixels into the original image plane, or by projecting the image pixels into the resampling plane. This may be helpful when the reprojection is simpler in the reverse direction, e.g., the projections typically used for the Digitized Sky Surveys.
An implementation in Java of this algorithm can resample megapixel images in ~2 seconds. The approach is trivially parallelizable to handle much large regions very rapidly.
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.