/**
 * Compute a capped **backing-store** size for a composite canvas.
 *
 * The canvas's CSS display size stays `width × height`; only the backing store
 * (the `<canvas width=… height=…>` intrinsic pixels) is downscaled so its area
 * never exceeds `maxCanvasPixels`. A phone-sized cap (~0.8 MP) keeps iOS
 * Safari's per-process canvas budget from blowing up on large-format artwork
 * (dielines / packaging), where a full page×zoom composite would be tens of
 * megapixels and cause WebKit to drop content. Downscale only — with no cap, or
 * an already-small canvas, the backing equals the display size.
 *
 * Shared by `SeparationCanvas` and `LayerCanvas` so the two composite surfaces
 * cap identically.
 */
export declare function cappedBacking(width: number, height: number, maxCanvasPixels?: number): {
    bw: number;
    bh: number;
};
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