import { DeepPartial } from './deep-partial';
/**
 * Resize and square-crop an image file for use as an avatar.
 *
 * The image is center-cropped to a square, scaled down to at most {@link size} pixels,
 * and converted to the specified output format.
 *
 * @param file - The source image file.
 * @param size - Max dimension in pixels for the output image.
 * @param extension - Output format. Use `"inherit"` to keep the original format.
 * @returns A promise that resolves to the processed `File`.
 */
export declare function resizeAvatar(file: File, size?: number, extension?: "png" | "jpg" | "webp" | "inherit"): Promise<File>;
/**
 * Convert a `File` to a base64-encoded data URL string.
 *
 * @param file - The file to encode.
 * @returns A promise that resolves to the base64 data URL.
 */
export declare function fileToBase64(file: File): Promise<string>;
/**
 * Convert an avatar to a compact data URL for the no-uploader fallback.
 *
 * Better Auth can cache the complete session user in a response cookie. Keeping
 * embedded avatars below a conservative byte limit prevents the image from
 * overflowing HTTP response headers while preserving higher-quality files for
 * configured upload providers.
 *
 * @param file - The resized avatar file to encode.
 * @returns A promise that resolves to a compact WebP data URL.
 */
export declare function fileToAvatarDataUrl(file: File): Promise<string>;
/**
 * Recursively merge `source` into `target`, producing a new object.
 *
 * - Plain objects are merged key-by-key; nested objects are merged recursively.
 * - `undefined` values in `source` are skipped (existing `target` values are preserved).
 * - Non-plain values (arrays, `Date`, `RegExp`, primitives, functions) in `source`
 *   replace the corresponding `target` value outright.
 *
 * @param target - The base object.
 * @param source - Partial overrides to apply on top of `target`.
 * @returns A new merged object of type `T`.
 */
export declare function deepmerge<T>(target: T, source: DeepPartial<T>): T;