gnodraw

Realm gno.land/r/g1v7s3j506wqul2zwt90awgjphpx4ztwga0926f7/gnodraw/v0: a 1250 x 800 (one million pixels, 16:10) pay-per-pixel canvas built on gno.land/p/g1v7s3j506wqul2zwt90awgjphpx4ztwga0926f7/canvas/v0.

Paint from the CLI:

1gnokey maketx call -pkgpath gno.land/r/g1v7s3j506wqul2zwt90awgjphpx4ztwga0926f7/gnodraw/v0 -func PaintBatch \
2  -args "10,10,6;11,10,6" -send 100000ugnot \
3  -gas-fee 1000000ugnot -gas-wanted 5000000 -broadcast -chainid dev -remote 127.0.0.1:26657 <key>

The amount sent must equal Price() times the number of pixels, and the call must come directly from a user transaction. Payments are forwarded to the admin wallet (Owner()) as they arrive; the admin paints for free and can SetPrice, SetMaxBatch, Withdraw and TransferOwnership (all params are owner-settable at runtime). Read functions used by clients: GetWidth, GetHeight, Price, Palette, MaxBatchSize, Painted, Pixel(x, y), Rows(from, to), Version(), DirtyRows(since).

Version() counts successful paint calls and DirtyRows(since) lists the rows touched after that version, so clients fetch only what changed.