This entire repository contains tools designed to facilitate spriting for The Legend of Zelda: A Link to the Past on the SNES.
PNGto4BPP converts a composite .png sprite sheet into a useable .spr file for importing into ROMs.
SpriteAnimator imports .spr files and manipulates them into a close emulation of the in-game animations.
SpriteFilter imports .spr files, applies any one of a number of atrocious filters, and then exports to a new .spr for importing into ROMs.