import type { StructuredGridImage } from "./types.js";
/** First non-empty trimmed string from format-specific alt/caption/title fields. */
export declare function normalizeImageAlt(...candidates: Array<string | null | undefined>): string;
/** Plaintext lines for the page reader when an image block carries alt text. */
export declare function narrationImageLines(...candidates: Array<string | null | undefined>): Array<string>;
export declare function structuredImageUrl(block: {
    blob?: unknown;
    externalSrc?: string;
}, did: string): string | null;
export declare function structuredImageAspectRatio(block: {
    aspectRatio?: {
        width?: number;
        height?: number;
    };
}): number;
export declare function structuredImageHasSource(block: {
    blob?: unknown;
    externalSrc?: string;
}): boolean;
/** Parse Offprint `#gridImage` entries (`blob` or legacy `image` field). */
export declare function parseStructuredGridImage(value: unknown): StructuredGridImage | null;
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