export interface Vec2 {
    x: number;
    y: number;
}
export interface PageRect {
    width: number;
    height: number;
}
export interface FoldLine {
    x1: number;
    y1: number;
    x2: number;
    y2: number;
}
export interface Fold {
    /** Crease line, clipped to the page rect (page-local coords). */
    foldLine: FoldLine;
    /** Crease orientation in radians (atan2 of the crease direction). */
    angle: number;
    /** Fold-shadow intensity, 0..1. */
    shadowAlpha: number;
}
/**
 * Book-fold geometry from a dragged corner.
 *
 * The folded flap reflects the grabbed `corner` onto the pointer `point`, so the
 * crease is the perpendicular bisector of the segment corner→point. Coordinates
 * are page-local: (0,0) top-left, x right, y down, page spanning (0,0)..(width,height).
 */
export declare function foldFromPointer(point: Vec2, corner: Vec2, pageRect: PageRect): Fold;