/**
 * Resolves the file type from a File object or URL.
 * Prefers file.type if available, otherwise infers from URL extension.
 *
 * @param file - The File object (optional)
 * @param url - The URL string (optional)
 * @returns The resolved MIME type string, or empty string if unable to determine
 *
 * @example
 * ```ts
 * // From file object
 * resolveFileType(file, undefined) // 'image/jpeg'
 *
 * // From URL
 * resolveFileType(undefined, 'https://example.com/image.jpg') // 'image/jpeg'
 *
 * // Neither provided
 * resolveFileType(undefined, undefined) // ''
 * ```
 */
export declare function resolveFileType(file?: File, url?: string): string;
/**
 * Checks if a file is an image based on File object or URL.
 *
 * @param file - The File object (optional)
 * @param url - The URL string (optional)
 * @returns true if the file is an image, false otherwise
 *
 * @example
 * ```ts
 * // From file object
 * isImageFile(file, undefined) // true if file.type starts with 'image/'
 *
 * // From URL
 * isImageFile(undefined, 'https://example.com/image.jpg') // true
 *
 * // Neither provided
 * isImageFile(undefined, undefined) // false
 * ```
 */
export declare function isImageFile(file?: File, url?: string): boolean;