  Accurate measurement of gravitational shear from images of distant galaxies
is one of the most direct ways of studying the distribution of mass in the
universe. We describe an implementation of a technique that is based on the
shapelets formalism.
  The shapelets technique describes PSF and observed images in terms of
Gauss-Hermite expansions (Gaussians times polynomials). It allows the various
operations that a galaxy image undergoes before being registered in a camera
(gravitational shear, PSF convolution, pixelation) to be modeled in a single
formalism, so that intrinsic ellipticities can be derived in a single modeling
step.
  The resulting algorithm, and tests of it on idealized data as well as more
realistic simulated images from the STEP project, are described. Results are
very promising, with attained calibration accuracy better than four percent (1
percent for round PSFs) and PSF ellipticity correction better than a factor of
20. Residual calibration problems are discussed.
