import type { MotionOptions } from './types.js';
/**
 * Per-cell motion field (ALGORITHM.md §21).
 *
 * Integer throughout, like every other path here (§0), so a GPU implementation
 * can agree bit-for-bit instead of drifting. That rules out the float smoothstep
 * and sqrt the effect is usually written with; both are done in fixed point
 * below, and the integer square root is the adjusted kind so a shader's
 * imprecise `sqrt` lands on the same value.
 */
export interface MotionField {
    columns: number;
    rows: number;
    /** Per-cell 0..255: 0 still, 255 moving hard. Row-major, `columns · rows`. */
    magnitude: Uint8Array;
}
/**
 * Retained state for a motion field: the previous frame's per-cell mean luma and
 * the decaying trail. Band-local, and the caller owns keeping it with the band
 * it describes — the same contract `BandReuse` carries.
 */
export interface MotionState {
    columns: number;
    rows: number;
    luma: Uint8Array;
    trail: Uint8Array;
    primed: boolean;
}
export declare function createMotionState(columns: number, rows: number): MotionState;
/**
 * floor(sqrt(n)) for n ≥ 0, exact.
 *
 * `Math.sqrt` is correctly rounded and WGSL's is not, so neither can be floored
 * and trusted near a perfect square. The adjustment makes both exact from any
 * starting estimate that is close, which is what lets the two implementations
 * agree.
 */
export declare function isqrt(n: number): number;
/**
 * Advance `state` by one frame of reduced samples and return the field.
 *
 * `reduced` is reduce-v1 output (§4) for this band: `columns · 8` by `rows · 8`
 * RGBA samples. Cells are read exactly as §5 reads them, so the motion field is
 * defined over the same mean luma the matcher already computes — it just is not
 * emitted there, and deriving it here keeps structural-v1 and its conformance
 * contract untouched.
 */
export declare function motionField(reduced: Uint8Array, columns: number, rows: number, state: MotionState, options?: MotionOptions): MotionField;