@syncfusion/ej2-pdf/src/pdf/core/graphics/images/png-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';
/**
 * PNG image decoder that parses PNG chunks, inflates compressed data,
 * applies PNG scanline filters None/Sub/Up/Average/Paeth, reconstructs
 * pixels (including alpha/mask when present), and exposes a PDF image stream.
 *
 * @private
 */
export declare class _PngDecoder extends _ImageDecoder {
    /**
     * Indicates whether the PNG uses an RGB color model.
     *
     * @private
     */
    _isRedGreenBlue: boolean;
    /**
     * Indicates whether grayscale shades are used.
     *
     * @private
     */
    _shades: boolean;
    /**
     * Internal flag controlling IDAT/deflate decode sequence.
     *
     * @private
     */
    _ideateDecode: boolean;
    /**
     * Number of color components present in the PNG.
     *
     * @private
     */
    _colors: number;
    /**
     * Bits per pixel after expansion according to color type and depth.
     *
     * @private
     */
    _bitsPerPixel: number;
    /**
     * Total concatenated length of all IDAT chunks.
     *
     * @private
     */
    _idatLength: number;
    /**
     * Number of input bands processed per scanline.
     *
     * @private
     */
    _inputBands: number;
    /**
     * Indicates whether the image data has been decoded.
     *
     * @private
     */
    _isDecode: boolean;
    /**
     * Length of the currently parsed PNG chunk.
     *
     * @private
     */
    _currentChunkLength: number;
    /**
     * Parsed IHDR and related header information.
     *
     * @private
     */
    _header: _PngHeader;
    /**
     * Accumulated compressed bytes extracted from IDAT chunks.
     *
     * @private
     */
    _encodedStream: Uint8Array;
    /**
     * Logical length of encoded stream (since we pre-allocate).
     *
     * @private
     */
    _encodedStreamLength: number;
    /**
     * Extracted mask channel data if available.
     *
     * @private
     */
    _maskData: Uint8Array;
    /**
     * Color space parameters resolved for this PNG image.
     *
     * @private
     */
    _colorSpace: any[];
    /**
     * Raw alpha channel bytes extracted from the PNG.
     *
     * @private
     */
    _alpha: Uint8Array;
    /**
     * Working buffer containing filtered/unfiltered scanline data.
     *
     * @private
     */
    _dataStream: Uint8Array;
    /**
     * Output buffer holding fully decoded pixel values.
     *
     * @private
     */
    _decodedImageData: Uint8Array;
    /**
     * Current read offset into the data stream buffer.
     *
     * @private
     */
    _dataStreamOffset: number;
    /**
     * Initializes a new instance of the `_PngDecoder` class.
     *
     * @private
     * @param {Uint8Array} stream byte array.
     */
    constructor(stream: Uint8Array);
    /**
     * Iterates through the PNG stream, reading chunk headers and dispatching
     * handlers (IHDR, IDAT, PLTE, tRNS, etc.) until end of image or stream end.
     *
     * @private
     * @returns {void}
     */
    _initialize(): void;
    /**
     * Reads the next chunk length and type, mapping it to an internal chunk enum.
     *
     * @private
     * @param {_PngChunkTypes} type Placeholder for the detected chunk type (ignored input).
     * @returns {{type: _PngChunkTypes, hasValidChunk: boolean}} The detected type and whether a valid chunk is available.
     */
    _hasValidChunkType(type: _PngChunkTypes): {
        type: _PngChunkTypes;
        hasValidChunk: boolean;
    };
    /**
     * Skips over the current chunk payload and CRC.
     *
     * @private
     * @returns {void}
     */
    _ignoreChunk(): void;
    /**
     * Parses the IHDR chunk and initializes decoder fields such as dimensions,
     * bit depth, color type, interlace, and derived attributes.
     *
     * @private
     * @returns {void}
     */
    _readHeader(): void;
    /**
     * Computes input bands, IDAT storage length hints, and effective bytes-per-pixel
     * based on color type and bit depth.
     *
     * @private
     * @returns {void}
     */
    _setBitsPerPixel(): void;
    /**
     * Appends the current IDAT chunk payload to the internal compressed buffer
     * and advances the stream position past CRC.
     *
     * @private
     * @returns {void}
     */
    _readImageData(): void;
    /**
     * Reads the PLTE palette for indexed color images and prepares the
     * Indexed color space structure in PDF terms.
     *
     * @private
     * @returns {void}
     */
    _readPhotoPlate(): void;
    /**
     * Reads the tRNS transparency table  and caches the
     * alpha bytes while detecting partial  transparency.
     *
     * @private
     * @returns {void}
     */
    _readTransparency(): void;
    /**
     * Resolves the effective PDF color space for the image. Returns either
     * `DeviceGray`/`DeviceRGB` or a calibrated `CalRGB` array when sRGB is present.
     *
     * @private
     * @returns {any} A color space name object or an array describing a calibrated RGB space.
     */
    _getPngColorSpace(): any;
    /**
     * Determines whether raw decode is required interlaced, 16-bit, or with alpha/shades.
     * If so, inflates IDAT data, allocates buffers, and reconstructs pixels; otherwise
     * reuses the encoded stream directly.
     *
     * @private
     * @returns {void}
     */
    _decodeImageData(): void;
    /**
     * Inflates the zlib-compressed IDAT payload omitting zlib header and Adler-32 trailer
     * into a raw byte array.
     *
     * @private
     * @param {Uint8Array} data The zlib-wrapped IDAT bytes (concatenated).
     * @returns {Uint8Array} The inflated byte array.
     */
    _getDeflatedData(data: Uint8Array): Uint8Array;
    /**
     * Dispatches pixel reconstruction by interlace method: a single pass for
     * non-interlaced images or seven Adam7 passes for interlaced images.
     *
     * @private
     * @returns {void}
     */
    _readDecodeData(): void;
    /**
     * Reconstructs scanlines for a pass/region by reading filter type, applying the
     * corresponding PNG filter, and writing pixels (and alpha/mask) to output buffers.
     *
     * @private
     * @param {number} xOffset Starting x offset in destination image for this pass.
     * @param {number} yOffset Starting y offset in destination image for this pass.
     * @param {number} xStep X stride (per Adam7 pass or 1 for non-interlaced).
     * @param {number} yStep Y stride (per Adam7 pass or 1 for non-interlaced).
     * @param {number} width Width of this pass/region in pixels.
     * @param {number} height Height of this pass/region in pixels.
     * @returns {void}
     */
    _decodeData(xOffset: number, yOffset: number, xStep: number, yStep: number, width: number, height: number): void;
    /**
     * Reads `count` bytes from a numeric array stream into `data` using the common
     * `_read` routine, returning the updated stream offset.
     *
     * @private
     * @param {Uint8Array} stream The source byte array.
     * @param {number} streamOffset The current read offset in the stream.
     * @param {Uint8Array} data The destination buffer to fill.
     * @param {number} count The number of bytes to read.
     * @returns {number} The new stream offset after reading.
     * @throws {Error} If insufficient data is available.
     */
    _readStream(stream: Uint8Array, streamOffset: number, data: Uint8Array, count: number): number;
    /**
     * Applies the PNG Sub filter (type 1) in-place to the current scanline.
     *
     * @private
     * @param {Uint8Array} data The scanline bytes to modify.
     * @param {number} count Number of bytes in the scanline row.
     * @param {number} bitsPerPixel Bytes-per-pixel (not bit-depth) for subtraction reference.
     * @returns {void}
     */
    _decompressSub(data: Uint8Array, count: number, bitsPerPixel: number): void;
    /**
     * Applies the PNG Up filter (type 2) in-place using the prior scanline.
     *
     * @private
     * @param {Uint8Array} data The current scanline bytes.
     * @param {Uint8Array} pData The prior scanline bytes.
     * @param {number} count Number of bytes per row.
     * @returns {void}
     */
    _decompressUp(data: Uint8Array, pData: Uint8Array, count: number): void;
    /**
     * Applies the PNG Average filter (type 3) in-place using left and prior values.
     *
     * @private
     * @param {Uint8Array} data The current scanline bytes.
     * @param {Uint8Array} pData The prior scanline bytes.
     * @param {number} count Number of bytes per row.
     * @param {number} bitsPerPixel Bytes-per-pixel (not bit-depth) for left reference.
     * @returns {void}
     */
    _decompressAverage(data: Uint8Array, pData: Uint8Array, count: number, bitsPerPixel: number): void;
    /**
     * Applies the PNG Paeth filter (type 4) in-place using left, up, and up-left predictors.
     *
     * @private
     * @param {Uint8Array} data The current scanline bytes.
     * @param {Uint8Array} pData The prior scanline bytes.
     * @param {number} count Number of bytes per row.
     * @param {number} bitsPerPixel Bytes-per-pixel (not bit-depth) for left reference.
     * @returns {void}
     */
    _decompressPaeth(data: Uint8Array, pData: Uint8Array, count: number, bitsPerPixel: number): void;
    /**
     * Computes the Paeth predictor from left (`a`), up (`b`), and up-left (`c`) neighbors.
     *
     * @private
     * @param {number} a The left pixel sample.
     * @param {number} b The above pixel sample.
     * @param {number} c The upper-left pixel sample.
     * @returns {number} The chosen predictor value.
     */
    _paethPredictor(a: number, b: number, c: number): number;
    /**
     * Converts a filtered scanline row to pixel values and writes them into the
     * decoded image buffer, also writing an 8-bit mask row when alpha/shades are present.
     *
     * @private
     * @param {Uint8Array} data The unfiltered scanline bytes for this pass.
     * @param {number} x Destination x start (accounting for pass offset).
     * @param {number} step Destination x increment (per Adam7 pass or 1).
     * @param {number} y Destination y coordinate.
     * @param {number} width The number of pixels to process from this row.
     * @returns {void}
     */
    _processPixels(data: Uint8Array, x: number, step: number, y: number, width: number): void;
    /**
     * Expands a scanline's filtered bytes into sample values based on bit depth:
     * 8-bit (1:1), 16-bit (merge pairs), or packed sub-byte samples.
     *
     * @private
     * @param {Uint8Array} data The scanline bytes.
     * @returns {Uint8Array | Uint16Array} The expanded per-sample values for the row.
     */
    _getPixel(data: Uint8Array): Uint8Array | Uint16Array;
    /**
     * Writes one pixel or scalar sample to the destination buffer, handling
     * 8/16-bit storage or sub-byte packing as required.
     *
     * @private
     * @param {Uint8Array} imageData The destination buffer (image or mask).
     * @param {Uint8Array | Uint16Array} data The source per-sample array.
     * @param {number} offset Offset into source sample array.
     * @param {number} size Number of samples to write (1=gray/alpha, 3=RGB).
     * @param {number} x Destination x coordinate.
     * @param {number} y Destination y coordinate.
     * @param {number} bitDepth Source bit depth (8/16 or packed).
     * @param {number} bpr Bytes-per-row in the destination buffer.
     * @returns {void}
     */
    _setPixel(imageData: Uint8Array, data: Uint8Array | Uint16Array, offset: number, size: number, x: number, y: number, bitDepth: number, bpr: number): void;
    /**
     * Builds the PDF image stream for the PNG image, wiring the
     * core dictionary entries, optional `FlateDecode`, and optional `DecodeParms`,
     * and attaches the mask if present.
     *
     * @private
     * @returns {_PdfStream} The image stream suitable for embedding.
     */
    _getImageDictionary(): _PdfStream;
    /**
     * Creates and assigns the soft-mask image stream from the alpha (or shades)
     * buffer when available.
     *
     * @private
     * @returns {void}
     */
    _setMask(): void;
    /**
     * Creates the `DecodeParms` dictionary (Columns/Colors/Predictor/BitsPerComponent)
     * for use with `FlateDecode` streams.
     *
     * @private
     * @returns {_PdfDictionary} The decode parameters dictionary.
     */
    _getDecodeParams(): _PdfDictionary;
    /**
     * Maps a 4 character PNG chunk label to the internal enum value.
     *
     * @private
     * @param {string} chunk The chunk name.
     * @returns {_PngChunkTypes} The mapped chunk type or `null` if unknown.
     */
    _getChunkType(chunk: string): _PngChunkTypes;
    /**
     * Maps a numeric filter byte to the corresponding PNG filter type enum.
     *
     * @private
     * @param {number} type The PNG filter byte (0..4).
     * @returns {_PngFilterTypes} The filter enum value.
     */
    _getFilterType(type: number): _PngFilterTypes;
    /**
     * Releases decoder-held buffers and references to allow GC.
     *
     * @private
     * @returns {void}
     */
    dispose(): void;
}
/**
 * Holds parsed values from the PNG `IHDR` chunk, including size, color type,
 * compression, filter method, and interlace mode; used to guide decoding.
 *
 * @private
 */
declare class _PngHeader {
    constructor();
    _width: number;
    _height: number;
    _colorType: number;
    _compression: number;
    _bitDepth: number;
    _filter: _PngFilterTypes;
    _interlace: number;
}
/**
 * Enumerates PNG chunk types recognized by the decoder, including core chunks
 * and optional metadata/ancillary chunks.
 *
 * @private
 */
declare enum _PngChunkTypes {
    iHDR = 0,
    pLTE = 1,
    iDAT = 2,
    iEND = 3,
    bKGD = 4,
    cHRM = 5,
    gAMA = 6,
    hIST = 7,
    pHYs = 8,
    sBIT = 9,
    tEXt = 10,
    tIME = 11,
    tRNS = 12,
    zTXt = 13,
    sRGB = 14,
    iCCP = 15,
    iTXt = 16,
    unknown = 17
}
/**
 * Enumerates the PNG scanline filter types applied to each row before compression.
 * These filters improve Deflate efficiency by transforming pixel values:
 *  - `none`    : No filtering applied.
 *  - `sub`     : Uses the left pixel as predictor.
 *  - `up`      : Uses the pixel above as predictor.
 *  - `average` : Averages the left and above pixels.
 *  - `paeth`   : Applies the Paeth predictor using left, above, and upper-left.
 *
 * @private
 */
declare enum _PngFilterTypes {
    none = 0,
    sub = 1,
    up = 2,
    average = 3,
    paeth = 4
}
export {};