/**
 * MarchingSquares — Extract vector contours from a 2D voxel label grid.
 *
 * For each label, produces a `Path2D` whose subpaths are small per-cell
 * polygons. The polygons tile the region occupied by the target label; the
 * union (via `ctx.fill(path, 'nonzero')`) is the label's silhouette on the
 * voxel grid.
 *
 * Coordinate convention:
 *   - Voxel (i, j) occupies the unit square [i, i+1] × [j, j+1] in render
 *     space, with its center at (i+0.5, j+0.5). This matches ITK-SNAP /
 *     standard imaging viewers and the existing `renderSliceToCanvas`
 *     `scale(scaledW / W, scaledH / H)` mapping.
 *   - Marching squares treats voxels as point samples at their centers:
 *     cell (i, j) has corners at voxel centers (i+0.5, j+0.5),
 *     (i+1.5, j+0.5), (i+1.5, j+1.5), (i+0.5, j+1.5).
 *   - This produces 45°-cut contours (diamonds for isolated voxels, rounded
 *     corners for connected regions) that stay within the voxel-square
 *     bounds, so the rendered silhouette is a slightly-inset version of the
 *     ITK-SNAP silhouette with smooth diagonals.
 *
 * Saddle cases (5 and 10) use a fixed convention: the two in-corners are
 * treated as disconnected within the cell (4-connectivity interpretation).
 */
export interface ContourBBox {
    /** Inclusive left voxel (0 ≤ x0 ≤ width). */
    x0: number;
    /** Inclusive top voxel (0 ≤ y0 ≤ height). */
    y0: number;
    /** Exclusive right voxel (x1 > x0). */
    x1: number;
    /** Exclusive bottom voxel (y1 > y0). */
    y1: number;
}
/** A single polygon's vertices in voxel-space coordinates. */
export type ContourPolygon = ReadonlyArray<readonly [number, number]>;
/**
 * Emit polygons covering the voxels where `labels === targetLabel`.
 * Pure geometry function — no Canvas dependency. Consumers can build a Path2D
 * (see {@link extractLabelContours}) or walk the vertex arrays directly
 * (tests, export, stroke rendering).
 *
 * Boundary cells (marching-squares cases 1–14) emit their cut polygon as
 * usual. Solid interior (case 15) is **coalesced into horizontal run-length
 * rectangles** instead of one unit square per cell, collapsing the subpath
 * count from O(area) to ≈ O(perimeter + rows). The filled region is
 * pixel-identical (contiguous full-cell squares tile exactly into a rectangle
 * with the same TL→TR→BR→BL winding), which is what keeps slice-scrubbing
 * fast on large masks without changing the rendered silhouette.
 */
export declare function extractLabelPolygons(labels: Uint8Array, width: number, height: number, targetLabel: number, stride?: number, channelOffset?: number, bbox?: ContourBBox): ContourPolygon[];
/**
 * Extract a `Path2D` covering all voxels equal to `targetLabel`.
 *
 * @param labels      Flat label array. Addressed as
 *                    `labels[(y * width + x) * stride + channelOffset]`.
 * @param width       Grid width in voxels.
 * @param height      Grid height in voxels.
 * @param targetLabel Label value to extract (1..255; 0 is background).
 * @param stride      Bytes per voxel (default 1). Use MaskVolume.numChannels
 *                    when reading interleaved slices.
 * @param channelOffset Offset within each voxel's channels to sample.
 *                    Default 0 (first channel = label id).
 * @param bbox        Optional voxel-space bbox to limit extraction.
 *                    Cells in a 1-voxel halo around the bbox are still
 *                    visited so the contour closes correctly at the bbox edges.
 */
export declare function extractLabelContours(labels: Uint8Array, width: number, height: number, targetLabel: number, stride?: number, channelOffset?: number, bbox?: ContourBBox): Path2D;
/**
 * Detect the distinct non-zero labels present in a slice region.
 *
 * @param labels        Flat label array (see {@link extractLabelContours}).
 * @param width         Grid width.
 * @param height        Grid height.
 * @param stride        Bytes per voxel.
 * @param channelOffset Offset within each voxel.
 * @param bbox          Optional region to scan (defaults to full grid).
 * @returns Sorted array of distinct label values (0 omitted).
 */
export declare function findLabelsInSlice(labels: Uint8Array, width: number, height: number, stride?: number, channelOffset?: number, bbox?: ContourBBox): number[];