idea 27 · build only
Photo lightbox
Pinch into an object until the brush marks separate.
Museo Nacional del Prado, Second Canvas
Bosch's Garden of Earthly Delights is published in gigapixel, so a phone can go past what you could see standing in front of it.
https://www.secondcanvas.net/museo-del-prado/
A Sunday on La Grande Jatte — 1884, Georges Seurat, 1884–86, border added 1888–89. Art Institute of Chicago, CC0. Pinch with two fingers, or drag with one. Double tap to jump in.
At three times, the dots start to separate. That is the whole argument for deep zoom on a phone: you can get closer than the rope lets you stand.
Pinch, drag, wheel, double tap, and buttons for anybody who cannot do any of those. It uses no library at all, just one transform and some clamping. For a gigapixel scan you swap the single image for a IIIF tile source and the gesture code stays exactly as it is.