Function paeth

packages/engine/src/utils/alphaBlit.ts:12–20

(a: number, b: number, c: number)

// ── PNG decoder ───────────────────────────────────────────────────────────────

function paeth(a: number, b: number, c: number): number {
  const p = a + b - c;
  const pa = Math.abs(p - a);
  const pb = Math.abs(p - b);
  const pc = Math.abs(p - c);
  if (pa <= pb && pa <= pc) return a;
  if (pb <= pc) return b;
  return c;
}

/**
 * Shared PNG chunk parsing + filter reconstruction.