/**
 * Document-level spread detection.
 *
 * Aspect ratio alone cannot identify a spread: an A4 spread (1.41) has the
 * same aspect as a single A4 landscape page, and 16:9 slide decks (1.78) sit
 * between Letter spreads (1.55) and square-page spreads (2.0). The reliable
 * signal is CONTENT evidence: a true spread has an empty vertical gutter at
 * the midline (elements do not cross it) and often carries a folio pair
 * (adjacent page numbers printed on the two halves, e.g. 736|737).
 *
 * The decision is made once per document, not per page, so evidence-free
 * pages (a full-bleed cover photo) follow the document verdict instead of
 * being left unsplit in an otherwise split document.
 */
import { type SpreadCandidateElement, type SpreadCandidatePage, type SpreadDetectionResult, type SpreadPageEvidence } from './types.js';
/** A page is a spread candidate only when clearly landscape. */
export declare function isLandscapePage(page: {
    width: number;
    height: number;
}): boolean;
/**
 * True when the element extends beyond the vertical midline by more than the
 * slack margin on BOTH sides. Touching the centerline is not crossing.
 */
export declare function crossesMidline(element: SpreadCandidateElement, pageWidth: number): boolean;
/**
 * Folio pair: two numeric-only text elements inside the top or bottom margin
 * band, one on each half, with adjacent values (left = right - 1 in LTR
 * publications, either order accepted). Strong direct evidence that the two
 * halves are distinct numbered pages.
 */
export declare function hasFolioPair(page: SpreadCandidatePage): boolean;
/** Gather per-page spread evidence. Exported for the orchestrator's logging. */
export declare function collectPageEvidence(page: SpreadCandidatePage): SpreadPageEvidence;
/**
 * Decide once for the whole document whether landscape pages are spreads.
 * Requires a clear majority of eligible landscape pages voting spread, with
 * an absolute minimum of votes so one odd page cannot flip a document.
 */
export declare function detectSpreadDocument(pages: SpreadCandidatePage[]): SpreadDetectionResult;
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