/**
 * XYWHFragment
 *
 * Represents a rectangular viewport region in image coordinates.
 * Matches Universal Viewer's XYWHFragment behavior for viewport serialization.
 */
export declare class XYWHFragment {
    x: number;
    y: number;
    w: number;
    h: number;
    constructor(x: number, y: number, w: number, h: number);
    /**
     * Serialize to string format: "x,y,w,h"
     */
    toString(): string;
    /**
     * Parse from string format: "xywh=x,y,w,h" or "x,y,w,h"
     */
    static fromString(bounds: string): XYWHFragment;
}