/** Image extensions accepted as theme/deck assets. Lowercase. */
export declare const IMAGE_EXTS: readonly [".png", ".jpg", ".jpeg", ".gif", ".svg", ".webp", ".bmp", ".ico"];
export declare const IMAGE_MIME_BY_EXT: Record<string, string>;
export declare function isImageFilename(filename: string): boolean;
/** List image filenames in a theme's `assets/` directory. Empty if the dir doesn't exist. */
export declare function scanThemeAssets(themeDir: string): Promise<string[]>;
/** Build a map of theme-asset filename → data URI for HTML-export embedding. */
export declare function buildThemeAssetDataURIMap(themeDir: string): Promise<Map<string, string>>;
/** Copy a theme's assets/ directory into a target directory's assets/ subdir. */
export declare function copyThemeAssets(themeDir: string, targetDir: string): Promise<void>;
/**
 * Sanitise a desired asset filename and resolve a non-colliding path inside the target dir.
 * Returns the chosen filename (relative to targetDir).
 */
export declare function chooseAssetFilename(targetDir: string, desiredName: string): Promise<string>;