Improve shearing time for high resolution images #18
Description
BATSim performance relative to galsim in affine shearing of galaxies becomes increasingly poor for high resolution images, even when accounting for GalSim drawing times.
By the time an image is 256x256, BATSim takes close to a second while GalSim is consistently under a tenth of a second. I think this is likely because GalSim is doing a lot of operations in Fourier space? It would be good to look into if there is optimisations that can be done here to bing the BATSim time down.