@cantoo/pdf-lib/es/core/streams/decode.js

Create and modify PDF files with JavaScript

import { UnexpectedObjectTypeError, UnsupportedEncodingError } from '../errors.js';
import PDFArray from '../objects/PDFArray.js';
import PDFDict from '../objects/PDFDict.js';
import PDFName from '../objects/PDFName.js';
import PDFNumber from '../objects/PDFNumber.js';
import Ascii85Stream from './Ascii85Stream.js';
import AsciiHexStream from './AsciiHexStream.js';
import FlateStream from './FlateStream.js';
import LZWStream from './LZWStream.js';
import RunLengthStream from './RunLengthStream.js';
import Stream from './Stream.js';
const decodeStream = (stream, encoding, params) => {
    if (encoding === PDFName.of('FlateDecode')) {
        return new FlateStream(stream);
    }
    if (encoding === PDFName.of('LZWDecode')) {
        let earlyChange = 1;
        if (params instanceof PDFDict) {
            const EarlyChange = params.lookup(PDFName.of('EarlyChange'));
            if (EarlyChange instanceof PDFNumber) {
                earlyChange = EarlyChange.asNumber();
            }
        }
        return new LZWStream(stream, undefined, earlyChange);
    }
    if (encoding === PDFName.of('ASCII85Decode')) {
        return new Ascii85Stream(stream);
    }
    if (encoding === PDFName.of('ASCIIHexDecode')) {
        return new AsciiHexStream(stream);
    }
    if (encoding === PDFName.of('RunLengthDecode')) {
        return new RunLengthStream(stream);
    }
    throw new UnsupportedEncodingError(encoding.asString());
};
export const decodePDFRawStream = ({ dict, contents, transform, }) => {
    let stream = new Stream(contents);
    if (transform) {
        stream = transform.createStream(stream, contents.length);
    }
    const Filter = dict.lookup(PDFName.of('Filter'));
    const DecodeParms = dict.lookup(PDFName.of('DecodeParms'));
    if (Filter instanceof PDFName) {
        stream = decodeStream(stream, Filter, DecodeParms);
    }
    else if (Filter instanceof PDFArray) {
        for (let idx = 0, len = Filter.size(); idx < len; idx++) {
            stream = decodeStream(stream, Filter.lookup(idx, PDFName), DecodeParms && DecodeParms.lookupMaybe(idx, PDFDict));
        }
    }
    else if (Filter) {
        throw new UnexpectedObjectTypeError([PDFName, PDFArray], Filter);
    }
    return stream;
};
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