Big photos and limits

Measured on an M4 MacBook and an iPhone (full numbers in the repository's PERF.md):

	12 MP	24 MP	48 MP
Photo on screen (iPhone)	0.15 s	0.26 s	0.53 s
Every slider drag (Mac and iPhone)	60 fps	60 fps	60 fps
Save as JPEG (iPhone)	0.5 s	0.9 s	1.9 s

How the editor keeps it fast

Rendering on the GPU (WebGL2). The work per frame depends on the screen size, not the photo size.
A preview copy for very large photos: the screen shows a copy at most 4096 px long; full detail loads when you zoom in far enough to see it.
Tiled export: photos larger than the GPU's texture limit (16,384 px on most desktops, less on phones) are exported in tiles at full size.
Memory: images and GPU memory are freed as soon as they're not needed — loading ten photos in a row uses no more than loading one.

Without WebGL2

Some browsers or locked-down machines have no WebGL2. The editor falls back to Canvas2D with the same results, done on the CPU. It stays usable (it draws fewer pixels while you drag a slider and sharpens on release) but is slower with colour adjustments.

Limits worth knowing

The biggest output is limited by the browser's largest canvas: about 268 MP on desktop browsers, about 16.7 MP on iPhones and iPads. Beyond that the result is scaled down and result.downscaled is true — check it if exact size matters.
WebP on iPhones: Safari on iOS can't encode WebP and saves PNG instead. result.mimeType and result.fileName tell you what you got.
Formats in: whatever the browser decodes — JPEG, PNG, WebP, GIF, AVIF, BMP, ICO, SVG everywhere; HEIC in Safari. An unsupported file shows a clear message instead of an error.