Splits an image into a grid of tiles — a rows × columns grid or fixed tile sizes — and packages the PNG tiles with a tiles.json map and CSS sprite positions in a ZIP written inside the Worker. For animated GIFs the frames mode decodes the animation in pure JavaScript (colour tables, interlacing, transparency, disposal) and exports every frame, or every nth, as full-canvas PNGs with frames.json timing. The preview shows a contact sheet. Everything runs locally.