/**
 * Image Transformation Service
 *
 * Provides on-the-fly image resize, crop, format conversion, and quality
 * adjustment using the `sharp` library. Results are cached in an LRU
 * in-memory cache to avoid redundant processing.
 */
/** Options that can be specified via query parameters. */
export interface ImageTransformOptions {
    width?: number;
    height?: number;
    quality?: number;
    format?: "webp" | "avif" | "jpeg" | "png";
    fit?: "cover" | "contain" | "fill" | "inside" | "outside";
}
/**
 * Parse transform options from URL query parameters.
 * Returns `null` when no transformation is requested.
 */
export declare function parseTransformOptions(query: Record<string, string>): ImageTransformOptions | null;
/** Check whether a content type is a transformable image. */
export declare function isTransformableImage(contentType: string): boolean;
/**
 * Apply image transformations and return the result buffer + content type.
 */
export declare function transformImage(buffer: Buffer | Uint8Array, options: ImageTransformOptions): Promise<{
    data: Buffer;
    contentType: string;
}>;
/**
 * Simple LRU cache for transformed images.
 *
 * Entries expire after `maxAgeMs` (default: 1 hour) and the cache
 * evicts the oldest entry when `maxEntries` is exceeded.
 */
export declare class TransformCache {
    private cache;
    private readonly maxEntries;
    private readonly maxAgeMs;
    private readonly maxTotalBytes;
    private totalBytes;
    constructor(maxEntries?: number, maxAgeMs?: number, maxTotalBytes?: number);
    /** Build a deterministic cache key from file key + transform options. */
    buildKey(fileKey: string, options: ImageTransformOptions): string;
    get(cacheKey: string): {
        data: Buffer;
        contentType: string;
    } | null;
    set(cacheKey: string, data: Buffer, contentType: string): void;
}