/**
 * Object stream mode used when writing the compressed PDF.
 *
 * Values are the literal strings the engine expects on
 * {@code QPdfCompressionFlagsP.object_streams}.
 */
export declare enum ObjectStreamMode {
    /**
     * Pack indirect objects into object streams. Smallest output for PDF 1.5+ (default).
     */
    Generate = "generate",
    /**
     * Keep the input's object stream layout unchanged.
     */
    Preserve = "preserve",
    /**
     * Write every object as a top-level indirect object (no object streams).
     * Use when consumer tools cannot read object streams.
     */
    Disable = "disable"
}
/**
 * Configuration for the advanced compression pipeline.
 *
 * @example Web/email (strongest size reduction)
 * ```ts
 * const opts: AdvancedCompressionOptions = {
 *   jpegQuality: 70,
 *   targetImageDpi: 150,
 *   removeStructureTree: true,
 * };
 * ```
 *
 * @example Print quality
 * ```ts
 * const opts: AdvancedCompressionOptions = {
 *   jpegQuality: 90,
 *   targetImageDpi: 300,
 * };
 * ```
 */
export interface AdvancedCompressionOptions {
    /**
     * JPEG quality used when re-encoding images during optimization (1-100).
     * When set, automatically enables image optimization.
     *
     * Default: `null` (no image re-encoding).
     *
     * Where the re-encoding happens depends on {@link targetImageDpi}:
     * - `targetImageDpi` set (default 150): each image is downsampled and
     *   re-encoded at this quality.
     * - `targetImageDpi = null`: qpdf re-encodes images at this quality
     *   without changing pixel dimensions.
     */
    jpegQuality?: number | null;
    /**
     * Target DPI for image downsampling during advanced compression.
     * Images whose effective rendered DPI exceeds this value are
     * downsampled before re-encoding.
     *
     * Default: `150`. Set to `null` (or `0`) to disable downsampling.
     *
     * **Lossy** — once an image is downsampled it cannot be restored to its
     * original resolution.
     */
    targetImageDpi?: number | null;
    /** 4:4:4 chroma subsampling when true (better color), 4:1:1 when false. Default true. */
    highQualityImageSubsampling?: boolean;
    /** Remove the document structure tree before compression. Default false. */
    removeStructureTree?: boolean;
    /** Compress content streams using zlib/Flate. Default true. */
    compressStreams?: boolean;
    /** Re-compress already Flate-encoded streams using {@link compressionLevel}. Default true. */
    recompressFlate?: boolean;
    /** zlib compression level (0-9). Default 9. */
    compressionLevel?: number;
    /** Object stream mode used when writing the output PDF. Default {@link ObjectStreamMode.Generate}. */
    objectStreams?: ObjectStreamMode;
    /** Drop indirect objects that are not referenced from the catalog. Default true. */
    removeUnreferencedResources?: boolean;
    /** Merge a page's content streams so they Flate-compress together. Default true. */
    coalesceContents?: boolean;
    /** Decode generalized filters (FlateDecode, LZW, ASCII85, ASCIIHex) before re-encoding. Default true. */
    decodeGeneralizedStreams?: boolean;
    /** Minimum image width (pixels) for image optimization to apply. Default 0. */
    optimizeImagesMinWidth?: number;
    /** Minimum image height (pixels) for image optimization to apply. Default 0. */
    optimizeImagesMinHeight?: number;
    /** Minimum image area (width × height) for image optimization to apply. Default 0. */
    optimizeImagesMinArea?: number;
}
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