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

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

import { _PdfStream } from './../../base-stream';
import { _ImageFormat } from './../../enumerator';
/**
 * Base class for image decoders that read bytes from an underlying stream,
 * parse headers/metadata, and expose decoded image data and properties for PDF embedding.
 * Concrete implementations must provide header parsing and dictionary creation.
 *
 * @private
 */
export declare abstract class _ImageDecoder {
    /**
     * Source byte stream of the encoded image.
     *
     * @private
     */
    _stream: Uint8Array;
    /**
     * Detected or assigned image format.
     *
     * @private
     */
    _format: _ImageFormat;
    /**
     * Image height in pixels.
     *
     * @private
     */
    _height: number;
    /**
     * Image width in pixels.
     *
     * @private
     */
    _width: number;
    /**
     * Number of bits per color component.
     *
     * @private
     */
    _bitsPerComponent: number;
    /**
     * Decoded raw image data buffer.
     *
     * @private
     */
    _imageData: Uint8Array;
    /**
     * PDF stream holding the image XObject.
     *
     * @private
     */
    _imageStream: _PdfStream;
    /**
     * Optional soft mask stream.
     *
     * @private
     */
    _maskStream: _PdfStream;
    /**
     * Current read position within the source stream.
     *
     * @private
     */
    _position: number;
    /**
     * Number of color components in the decoded image.
     *
     * @private
     */
    _noOfComponents: number;
    /**
     * Resets the stream read position to the beginning.
     *
     * @private
     * @returns {void}
     */
    _reset(): void;
    /**
     * Reads a single byte from the underlying stream at the specified index without moving the cursor.
     *
     * @private
     * @param {number} index The zero based position in the stream to read from.
     * @returns {number} The byte value at the given index.
     */
    _getBuffer(index: number): number;
    /**
     * Reads a sequence of bytes either from the internal stream into a `Uint8Array` buffer,
     * or from a provided `stream` array into a numeric buffer, honoring the specified offset and count.
     *
     * @private
     * @param {Uint8Array | number[]} buffer The destination buffer to receive the read bytes.
     * @param {number} offset The starting offset in `buffer` at which to begin writing.
     * @param {number} count The number of bytes to read.
     * @param {number[]} [stream] Optional source byte array; when provided, bytes are copied from this array instead of the internal stream.
     * @returns {void | {outputBuffer: number[], offset: number, length: number}} Returns nothing when reading from the internal stream; when `stream` is provided, returns an object containing the written buffer, updated offset, and number of bytes written.
     */
    _read(buffer: Uint8Array, offset: number, count: number): void;
    _read(buffer: number[], offset: number, count: number, stream: number[]): {
        outputBuffer: number[];
        offset: number;
        length: number;
    };
    /**
     * Reads a string of the specified length from the current stream position using 8 bit char codes.
     *
     * @private
     * @param {number} length The number of characters to read.
     * @returns {string} The decoded string.
     */
    _readString(length: number): string;
    /**
     * Advances the current read position by the specified number of bytes.
     *
     * @private
     * @param {number} length The number of bytes to skip forward.
     * @returns {void}
     */
    _seek(length: number): void;
    /**
     * Reads a single byte from the current stream position and advances the cursor.
     *
     * @private
     * @returns {number} The next byte value.
     * @throws {Error} Throws if attempting to read beyond the end of the stream.
     */
    _readByte(): number;
    /**
     * Converts a number to an unsigned 16 bit value.
     *
     * @private
     * @param {number} value The input value to convert.
     * @returns {number} The unsigned 16 bit representation.
     */
    _toUnsigned16(value: number): number;
    /**
     * Reads a 32 bit unsigned integer from the stream at the specified offset.
     *
     * @private
     * @param {number} offset The byte offset at which to read the 32 bit value.
     * @returns {number} The 32 bit unsigned integer.
     */
    _readUnsigned32(offset: number): number;
    /**
     * Gets the image stream/dictionary that represents the decoded image data and metadata.
     *
     * @private
     * @returns {_PdfStream} The image dictionary/stream for embedding into the PDF.
     */
    abstract _getImageDictionary(): _PdfStream;
    /**
     * Initializes the decoder state from the source stream (e.g., header parsing, buffers).
     *
     * @private
     * @returns {void}
     */
    abstract _initialize(): void;
    /**
     * Parses and validates the image header, populating format, dimensions, and component info.
     *
     * @private
     * @returns {void}
     */
    abstract _readHeader(): void;
}