Space Telescope Science Institute
DrizzlePac 2012 Handbook
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The DrizzlePac Handbook > Appendix D: Previous Drizzle Software Packages > D.1 Introduction

D.1 Introduction
Since the drizzle algorithm was first introduced in 1996 for the processing of the original Hubble Deep Field observations, it's become the core of several software packages for correcting image distortion, identifying and cleaning cosmic rays, aligning and combining dithered images, to create a clean, distortion-free data product.
Original development of the Drizzle software was a collaborative effort by Andy Fruchter and Richard Hook ( The main code, written in Fortran77, was available as standalone executables, and also as an IRAF task in the STSDAS v2.0 Dither package.
Later, Drizzle1 software became the basis for a more automated task, called PyDrizzle, that was written in Python. It aligned images based on WCS information to produce distortion-corrected images.
In 2009, an automated Python task called MultiDrizzle was introduced. It implemented steps for identifying cosmic rays in images aligned by PyDrizzle, allowing images to be drizzle-combined with cosmic rays masks to create a final product free of cosmic rays.

The Python drizzle tasks could only be run in the PyRAF environment whereas the original IRAF drizzle tasks could be run from either PyRAF or the original IRAF command language, or cl environment.

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