/**
 * Zoom-from-origin math, ported from 2.x `utils.getSize`/`utils.getTransform`
 * (`src/lg-utils.ts`) as pure rect arithmetic. The framework layer measures
 * the DOM (trigger/container bounding rects) and passes plain numbers in.
 *
 * Note: this module follows the standing rule that pure functions needed
 * by the framework layers live in headless. It is distinct from
 * `zoom-math.ts` (zoom plugin).
 */
export interface ImageSize {
    width: number;
    height: number;
}
export interface RectLike {
    left: number;
    top: number;
    width: number;
    height: number;
}
/**
 * Parse an item's `lgSize` value (`"1920-1280"`, or a responsive list like
 * `"240-160-375, 1600-1067"` where the third number is the max viewport
 * width the entry applies to).
 */
export declare function parseImageSize(lgSize: string | undefined, viewportWidth: number): ImageSize | undefined;
/**
 * Fit a natural image size into the available container box, preserving
 * aspect ratio and never scaling up (2.x `utils.getSize` math).
 */
export declare function fitImageSize(size: ImageSize, containerWidth: number, containerHeight: number): ImageSize;
/**
 * Whether a measured trigger rect can anchor the zoom-from-origin flight.
 * A trigger that is hidden (`display: none`, the `hidden` attribute),
 * detached or collapsed measures 0×0 at the viewport origin; a flight
 * aimed at it would shrink the slide into the top-left corner.
 */
export declare function isUsableOriginRect(rect: RectLike | null | undefined): rect is RectLike;
/** Scale the closing slide shrinks to when it has no trigger to return to. */
export declare const CENTER_CLOSE_SCALE = 0.5;
/**
 * Close transform for a slide without a usable origin (hidden or
 * collapsed trigger, no `lgSize`): shrink in place about the stage centre,
 * the mirror of the `lg-start-zoom` open. The runtime pairs it with the
 * `lg-close-to-center` class, which fades the slide out over the same
 * duration.
 */
export declare function getCenterCloseTransform(scale?: number): string;
export interface OriginTransformInput {
    /** Bounding rect of the trigger thumbnail image, viewport coordinates. */
    triggerRect: RectLike;
    /** Bounding rect of the gallery outer element, viewport coordinates. */
    containerRect: RectLike;
    /** Media container top offset (toolbar height), px. */
    top: number;
    /** Media container bottom offset (caption + thumb strip height), px. */
    bottom: number;
    /** Final displayed image size (see {@link fitImageSize}). */
    imageSize: ImageSize;
}
/**
 * CSS transform that places the (centered, final-size) slide image exactly
 * over the trigger thumbnail — the starting point of the zoom-from-origin
 * open animation and the end point of the close animation.
 */
export declare function getOriginTransform(input: OriginTransformInput): string;