import type { WebXRImageTrackingModel } from "./WebXRImageTracking.js";
/**
 * Cache of decoded marker bitmaps, keyed by image url.
 * Also read by the USDZ exporter (see {@link WebXRImageTracking}) to embed the marker into the .usdz.
 */
export declare const _imageElements: Map<string, ImageBitmap | null>;
/**
 * Resolve marker bitmaps for the given tracked-image models and append them to `args.trackedImages`
 * (the list handed to `navigator.xr.requestSession`).
 *
 * Every valid marker is awaited so that images which are still decoding when the XR session is
 * requested get included instead of being silently dropped (which previously caused markers to only
 * work after re-entering AR). Loading happens in parallel and never rejects: a marker that can not be
 * loaded is skipped individually so a single unavailable image can not fail the whole session request.
 *
 * @param models The configured tracked-image models
 * @param args The session init object; `trackedImages` is created if missing and appended to
 * @param load Injectable loader (defaults to {@link loadImage}); resolves the decoded bitmap or null
 * @returns Map of `trackedImages` index -> model for the appended images (used to resolve results)
 */
export declare function collectTrackedImages(models: readonly WebXRImageTrackingModel[] | undefined | null, args: {
    trackedImages?: Array<{
        image: ImageBitmap;
        widthInMeters: number;
    }>;
}, load?: (url: string) => Promise<ImageBitmap | null>): Promise<Map<number, WebXRImageTrackingModel>>;
/**
 * Load and decode a marker image into an {@link ImageBitmap}, caching it in {@link _imageElements}.
 * Idempotent: concurrent or repeated calls for the same URL share a single in-flight load.
 *
 * Resolves to `null` and never rejects when the image can not be fetched or decoded, so callers can
 * skip an unavailable marker without failing the surrounding XR session request. A failed load clears
 * its cache entry so a later attempt (e.g. re-entering AR) can retry.
 */
export declare function loadImage(url: string): Promise<ImageBitmap | null>;