export declare class DropFileAreaHelper {
    private _dropArea;
    private _viewer;
    private _onFileDrop;
    private _onImageUrlDrop;
    private _handlers;
    private _activated;
    constructor(_dropArea: HTMLElement, _viewer: any, //GcPdfViewer,
    _onFileDrop: (file: any, point: any) => void, _onImageUrlDrop: (imgUrl: any, point: any) => void);
    on(): void;
    off(): void;
    private _registerEvents;
    private _unregisterEvents;
    /**
     * A listener for the dragenter and dragover events are used to indicate valid drop targets
     * a dragged item enters a valid drop target
     **/
    private _dragEnter;
    /**
   * A listener for the dragenter and dragover events are used to indicate valid drop targets.
   * a dragged item is being dragged over a valid drop target, every few hundred milliseconds.
   **/
    private _dragOver;
    /**
     * a dragged item leaves a valid drop target.
     **/
    private _dragLeave;
    /**
     * an item is dropped on a valid drop target
     **/
    private _drop;
    private _handleFiles;
    /**
     * Returns canvas size if any.
     * @param canvas
     */
    static getCanvasSize(canvas?: HTMLCanvasElement): {
        h: number;
        w: number;
    };
    /**
     * Load Image from Url.
     * @param url
     */
    static loadImageFromUrl(url: string): Promise<HTMLImageElement | null>;
    /**
     * Gets image data from HTMLImageElement.
     * @param img
     */
    static imageToBytes(img: HTMLImageElement): Promise<Uint8Array | null>;
    /**
     * Returns result image blob data if any.
     **/
    static canvasToImageData(canvas?: HTMLCanvasElement): Promise<Uint8Array | null>;
}