codec / predictor · 2D / lossless

planar

Predict the local surface, not just one direction.

planar uses the west, north and north-west neighbours to continue the local slope: W + N − NW. It works especially well on smooth two-dimensional gradients, where a perfect plane becomes a stream of zeros. Along the top and left edges it falls back to a simple one-direction predictor.

ctid

0x72D703

header

uint32 · row width in samples
+ uint32 · plane count, when above one

widths

8 · 16 · 32 · 64-bit integers

decode

fold N−NW from the row above, then prefix-sum the row