/**
 * Mask Renderer
 *
 * Paints CSS mask-image layers into a mask surface (alpha mask) which the
 * caller composites onto the element surface via `destination-in`.
 *
 * Value grammars are shared with background-image (position/size/repeat), so
 * the layer maths mirrors the background renderer but works in the local
 * coordinate space of the mask positioning area (default: border box) and
 * always fills the whole area — a mask surface is about alpha coverage, not
 * about what is visible underneath.
 *
 * Gradient layers share the rasterisation primitives of the background
 * renderer (gradient-rasterizer.ts): repeating gradients stack their stop
 * cycles, and the area beyond a radial gradient's ending shape keeps the
 * last stop's colour. Limitations (v1): mask-mode is alpha-only; layers
 * composite with source-over (≈ the spec-default `add`).
 */
import { ICSSImage } from '../../css/types/image';
import { LengthPercentage } from '../../css/types/length-percentage';
import { BACKGROUND_REPEAT } from '../../css/property-descriptors/background-repeat';
import { BackgroundSizeInfo } from '../../css/property-descriptors/background-size';
export interface MaskLayerStyles {
    maskPosition: LengthPercentage[][];
    maskRepeat: BACKGROUND_REPEAT[];
    maskSize: BackgroundSizeInfo[][];
}
export interface MaskArea {
    left: number;
    top: number;
    width: number;
    height: number;
}
export type MaskImageSource = HTMLImageElement | HTMLCanvasElement;
/**
 * Paint every mask layer into `ctx` (expected to already be scaled to device
 * pixels and translated so the page origin maps correctly).
 */
export declare const paintMaskLayers: (ctx: CanvasRenderingContext2D, layers: ICSSImage[], styles: MaskLayerStyles, area: MaskArea, matchImage: (url: string) => Promise<MaskImageSource | undefined>) => Promise<void>;