@syncfusion/ej2-pdf/src/pdf/core/graphics/images/jpeg-decoder.d.ts

Feature-rich JavaScript PDF library with built-in support for loading and manipulating PDF document.

import { _ImageDecoder } from './image-decoder';
import { _PdfStream } from './../../base-stream';
import { _PdfDictionary } from './../../pdf-primitives';
/**
 * JPEG image decoder that parses the input stream, extracts width/height/components
 * from JPEG headers, and exposes a PDF image dictionary (DCTDecode).
 *
 * @private
 */
export declare class _JpegDecoder extends _ImageDecoder {
    /**
     * Initializes a new instance of the `_JpegDecoder` class.
     *
     * @private
     * @param {Uint8Array} stream byte array.
     */
    constructor(stream: Uint8Array);
    /**
     * Gets the raw image data buffer read from the source stream.
     *
     * @private
     * @returns {ArrayBuffer} The image data as a contiguous buffer.
     */
    readonly _imageDataAsNumberArray: ArrayBuffer;
    /**
     * Initializes decoder state for a JPEG stream: sets format, reads header to resolve
     * image properties, resets the cursor, and copies the full stream into `_imageData`.
     *
     * @private
     * @returns {void}
     */
    _initialize(): void;
    /**
     * Parses the JPEG header to determine image dimensions and component count.
     * Falls back to a streaming marker scan when the initial segment lengths exceed bounds.
     *
     * @private
     * @returns {void}
     */
    _readHeader(): void;
    /**
     * Builds PDF image stream for the decoded JPEG, wiring the
     * appropriate dictionary entries `Type`, `Subtype`, `Width`, `Height`, `BitsPerComponent`,
     * `Filter=DCTDecode`, `ColorSpace`, and `DecodeParms`.
     *
     * @private
     * @returns {_PdfStream} The populated PDF image stream.
     */
    _getImageDictionary(): _PdfStream;
    /**
     * Resolves the PDF color space name from the number of JPEG components.
     *
     * @private
     * @returns {string} Returns `'DeviceGray'` for 1 component, `'DeviceCMYK'` for 4 components, otherwise `'DeviceRGB'`.
     */
    _getColorSpace(): string;
    /**
     * Produces a `DecodeParms` dictionary suitable for DCTDecode images with predictor settings.
     *
     * @private
     * @returns {_PdfDictionary} The decode parameters dictionary.
     */
    _getDecodeParams(): _PdfDictionary;
    /**
     * Skips over a JPEG segment by reading its 2 byte length and advancing the cursor.
     * Throws if the segment length is invalid.
     *
     * @private
     * @returns {void}
     * @throws {Error} If the segment length is less than 2.
     */
    _skipStream(): void;
    /**
     * Scans the JPEG stream by markers to locate a Start of Frame (SOF) segment and
     * extracts height, width, and component count when the standard header walk exceeded bounds.
     *
     * @private
     * @returns {void}
     */
    _readExceededJpegImage(): void;
    /**
     * Reads the next JPEG marker (0xFF followed by a non-FF byte), skipping fill bytes.
     *
     * @private
     * @returns {number} The 16 bit marker value.
     * @throws {Error} If non marker bytes were skipped prior to 0xFF (invalid stream).
     */
    _getMarker(): number;
}