/**
* @license
* Copyright Google LLC All Rights Reserved.
*
* Use of this source code is governed by an MIT-style license that can be
* found in the LICENSE file at https://angular.io/license
*/
import { Renderer2 } from '@angular/core';
import * as i0 from "@angular/core";
/**
* @description Contains the logic needed to track and add preload link tags to the `` tag. It
* will also track what images have already had preload link tags added so as to not duplicate link
* tags.
*
* In dev mode this service will validate that the number of preloaded images does not exceed the
* configured default preloaded images limit: {@link DEFAULT_PRELOADED_IMAGES_LIMIT}.
*/
export declare class PreloadLinkCreator {
private readonly preloadedImages;
private readonly document;
/**
* @description Add a preload `` to the `` of the `index.html` that is served from the
* server while using Angular Universal and SSR to kick off image loads for high priority images.
*
* The `sizes` (passed in from the user) and `srcset` (parsed and formatted from `ngSrcset`)
* properties used to set the corresponding attributes, `imagesizes` and `imagesrcset`
* respectively, on the preload `` tag so that the correctly sized image is preloaded from
* the CDN.
*
* {@link https://web.dev/preload-responsive-images/#imagesrcset-and-imagesizes}
*
* @param renderer The `Renderer2` passed in from the directive
* @param src The original src of the image that is set on the `ngSrc` input.
* @param srcset The parsed and formatted srcset created from the `ngSrcset` input
* @param sizes The value of the `sizes` attribute passed in to the `` tag
*/
createPreloadLinkTag(renderer: Renderer2, src: string, srcset?: string, sizes?: string): void;
static ɵfac: i0.ɵɵFactoryDeclaration;
static ɵprov: i0.ɵɵInjectableDeclaration;
}