/**
 * Small internal helpers shared across the format parsers and the render-tree
 * builder. Deliberately not re-exported from `index.ts` — these are
 * implementation details, not part of the package's public API.
 *
 * This module has no local dependencies beyond {@link ./atproto/blob}, so it
 * stays a leaf in the import graph and can be pulled in anywhere without
 * risking a cycle.
 */
/** Narrow to a plain (non-array) object. */
export declare function isRecord(value: unknown): value is Record<string, unknown>;
/** The value unchanged when it is an absolute `http(s)` URL string, else null. */
export declare function externalHttpUrl(value: unknown): string | null;
/**
 * Width ÷ height for image layout. Returns {@link fallback} (16∶9 by default)
 * when either dimension is missing, non-numeric, or non-positive.
 */
export declare function aspectRatioFromDimensions(width: unknown, height: unknown, fallback?: number): number;
/**
 * Build a Bluesky CDN image URL from a blob ref + the repo's DID. Returns null
 * when the blob carries no CID. PNG is requested to preserve alpha.
 */
export declare function blobImageUrl(blob: unknown, did: string): string | null;
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