pdf.js/src/core/jbig2.js

/* Copyright 2012 Mozilla Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import { log2, readInt8, readUint16, readUint32, shadow } from '../shared/util';
import { ArithmeticDecoder } from './arithmetic_decoder';
import { CCITTFaxDecoder } from './ccitt';

let Jbig2Error = (function Jbig2ErrorClosure() {
  function Jbig2Error(msg) {
    this.message = 'JBIG2 error: ' + msg;
  }

  Jbig2Error.prototype = new Error();
  Jbig2Error.prototype.name = 'Jbig2Error';
  Jbig2Error.constructor = Jbig2Error;

  return Jbig2Error;
})();

var Jbig2Image = (function Jbig2ImageClosure() {
  // Utility data structures
  function ContextCache() {}

  ContextCache.prototype = {
    getContexts(id) {
      if (id in this) {
        return this[id];
      }
      return (this[id] = new Int8Array(1 << 16));
    },
  };

  function DecodingContext(data, start, end) {
    this.data = data;
    this.start = start;
    this.end = end;
  }

  DecodingContext.prototype = {
    get decoder() {
      var decoder = new ArithmeticDecoder(this.data, this.start, this.end);
      return shadow(this, 'decoder', decoder);
    },
    get contextCache() {
      var cache = new ContextCache();
      return shadow(this, 'contextCache', cache);
    },
  };

  // Annex A. Arithmetic Integer Decoding Procedure
  // A.2 Procedure for decoding values
  function decodeInteger(contextCache, procedure, decoder) {
    var contexts = contextCache.getContexts(procedure);
    var prev = 1;

    function readBits(length) {
      var v = 0;
      for (var i = 0; i < length; i++) {
        var bit = decoder.readBit(contexts, prev);
        prev = (prev < 256 ? (prev << 1) | bit :
                (((prev << 1) | bit) & 511) | 256);
        v = (v << 1) | bit;
      }
      return v >>> 0;
    }

    var sign = readBits(1);
    var value = readBits(1) ?
                  (readBits(1) ?
                    (readBits(1) ?
                      (readBits(1) ?
                        (readBits(1) ?
                          (readBits(32) + 4436) :
                        readBits(12) + 340) :
                      readBits(8) + 84) :
                    readBits(6) + 20) :
                  readBits(4) + 4) :
                readBits(2);
    return (sign === 0 ? value : (value > 0 ? -value : null));
  }

  // A.3 The IAID decoding procedure
  function decodeIAID(contextCache, decoder, codeLength) {
    var contexts = contextCache.getContexts('IAID');

    var prev = 1;
    for (var i = 0; i < codeLength; i++) {
      var bit = decoder.readBit(contexts, prev);
      prev = (prev << 1) | bit;
    }
    if (codeLength < 31) {
      return prev & ((1 << codeLength) - 1);
    }
    return prev & 0x7FFFFFFF;
  }

  // 7.3 Segment types
  var SegmentTypes = [
    'SymbolDictionary', null, null, null, 'IntermediateTextRegion', null,
    'ImmediateTextRegion', 'ImmediateLosslessTextRegion', null, null, null,
    null, null, null, null, null, 'PatternDictionary', null, null, null,
    'IntermediateHalftoneRegion', null, 'ImmediateHalftoneRegion',
    'ImmediateLosslessHalftoneRegion', null, null, null, null, null, null, null,
    null, null, null, null, null, 'IntermediateGenericRegion', null,
    'ImmediateGenericRegion', 'ImmediateLosslessGenericRegion',
    'IntermediateGenericRefinementRegion', null,
    'ImmediateGenericRefinementRegion',
    'ImmediateLosslessGenericRefinementRegion', null, null, null, null,
    'PageInformation', 'EndOfPage', 'EndOfStripe', 'EndOfFile', 'Profiles',
    'Tables', null, null, null, null, null, null, null, null,
    'Extension'
  ];

  var CodingTemplates = [
    [{ x: -1, y: -2, }, { x: 0, y: -2, }, { x: 1, y: -2, }, { x: -2, y: -1, },
     { x: -1, y: -1, }, { x: 0, y: -1, }, { x: 1, y: -1, }, { x: 2, y: -1, },
     { x: -4, y: 0, }, { x: -3, y: 0, }, { x: -2, y: 0, }, { x: -1, y: 0, }],
    [{ x: -1, y: -2, }, { x: 0, y: -2, }, { x: 1, y: -2, }, { x: 2, y: -2, },
     { x: -2, y: -1, }, { x: -1, y: -1, }, { x: 0, y: -1, }, { x: 1, y: -1, },
     { x: 2, y: -1, }, { x: -3, y: 0, }, { x: -2, y: 0, }, { x: -1, y: 0, }],
    [{ x: -1, y: -2, }, { x: 0, y: -2, }, { x: 1, y: -2, }, { x: -2, y: -1, },
     { x: -1, y: -1, }, { x: 0, y: -1, }, { x: 1, y: -1, }, { x: -2, y: 0, },
     { x: -1, y: 0, }],
    [{ x: -3, y: -1, }, { x: -2, y: -1, }, { x: -1, y: -1, }, { x: 0, y: -1, },
     { x: 1, y: -1, }, { x: -4, y: 0, }, { x: -3, y: 0, }, { x: -2, y: 0, },
     { x: -1, y: 0, }]
  ];

  var RefinementTemplates = [
    {
      coding: [{ x: 0, y: -1, }, { x: 1, y: -1, }, { x: -1, y: 0, }],
      reference: [{ x: 0, y: -1, }, { x: 1, y: -1, }, { x: -1, y: 0, },
                  { x: 0, y: 0, }, { x: 1, y: 0, }, { x: -1, y: 1, },
                  { x: 0, y: 1, }, { x: 1, y: 1, }],
    },
    {
      coding: [{ x: -1, y: -1, }, { x: 0, y: -1, }, { x: 1, y: -1, },
               { x: -1, y: 0, }],
      reference: [{ x: 0, y: -1, }, { x: -1, y: 0, }, { x: 0, y: 0, },
                  { x: 1, y: 0, }, { x: 0, y: 1, }, { x: 1, y: 1, }],
    }
  ];

  // See 6.2.5.7 Decoding the bitmap.
  var ReusedContexts = [
    0x9B25, // 10011 0110010 0101
    0x0795, // 0011 110010 101
    0x00E5, // 001 11001 01
    0x0195  // 011001 0101
  ];

  var RefinementReusedContexts = [
    0x0020, // '000' + '0' (coding) + '00010000' + '0' (reference)
    0x0008  // '0000' + '001000'
  ];

  function decodeBitmapTemplate0(width, height, decodingContext) {
    var decoder = decodingContext.decoder;
    var contexts = decodingContext.contextCache.getContexts('GB');
    var contextLabel, i, j, pixel, row, row1, row2, bitmap = [];

    // ...ooooo....
    // ..ooooooo... Context template for current pixel (X)
    // .ooooX...... (concatenate values of 'o'-pixels to get contextLabel)
    var OLD_PIXEL_MASK = 0x7BF7; // 01111 0111111 0111

    for (i = 0; i < height; i++) {
      row = bitmap[i] = new Uint8Array(width);
      row1 = (i < 1) ? row : bitmap[i - 1];
      row2 = (i < 2) ? row : bitmap[i - 2];

      // At the beginning of each row:
      // Fill contextLabel with pixels that are above/right of (X)
      contextLabel = (row2[0] << 13) | (row2[1] << 12) | (row2[2] << 11) |
                     (row1[0] << 7) | (row1[1] << 6) | (row1[2] << 5) |
                     (row1[3] << 4);

      for (j = 0; j < width; j++) {
        row[j] = pixel = decoder.readBit(contexts, contextLabel);

        // At each pixel: Clear contextLabel pixels that are shifted
        // out of the context, then add new ones.
        contextLabel = ((contextLabel & OLD_PIXEL_MASK) << 1) |
                       (j + 3 < width ? row2[j + 3] << 11 : 0) |
                       (j + 4 < width ? row1[j + 4] << 4 : 0) | pixel;
      }
    }

    return bitmap;
  }

  // 6.2 Generic Region Decoding Procedure
  function decodeBitmap(mmr, width, height, templateIndex, prediction, skip, at,
                        decodingContext) {
    if (mmr) {
      let input = new Reader(decodingContext.data, decodingContext.start,
        decodingContext.end);
      return decodeMMRBitmap(input, width, height, false);
    }

    // Use optimized version for the most common case
    if (templateIndex === 0 && !skip && !prediction && at.length === 4 &&
        at[0].x === 3 && at[0].y === -1 && at[1].x === -3 && at[1].y === -1 &&
        at[2].x === 2 && at[2].y === -2 && at[3].x === -2 && at[3].y === -2) {
      return decodeBitmapTemplate0(width, height, decodingContext);
    }

    var useskip = !!skip;
    var template = CodingTemplates[templateIndex].concat(at);

    // Sorting is non-standard, and it is not required. But sorting increases
    // the number of template bits that can be reused from the previous
    // contextLabel in the main loop.
    template.sort(function (a, b) {
      return (a.y - b.y) || (a.x - b.x);
    });

    var templateLength = template.length;
    var templateX = new Int8Array(templateLength);
    var templateY = new Int8Array(templateLength);
    var changingTemplateEntries = [];
    var reuseMask = 0, minX = 0, maxX = 0, minY = 0;
    var c, k;

    for (k = 0; k < templateLength; k++) {
      templateX[k] = template[k].x;
      templateY[k] = template[k].y;
      minX = Math.min(minX, template[k].x);
      maxX = Math.max(maxX, template[k].x);
      minY = Math.min(minY, template[k].y);
      // Check if the template pixel appears in two consecutive context labels,
      // so it can be reused. Otherwise, we add it to the list of changing
      // template entries.
      if (k < templateLength - 1 &&
          template[k].y === template[k + 1].y &&
          template[k].x === template[k + 1].x - 1) {
        reuseMask |= 1 << (templateLength - 1 - k);
      } else {
        changingTemplateEntries.push(k);
      }
    }
    var changingEntriesLength = changingTemplateEntries.length;

    var changingTemplateX = new Int8Array(changingEntriesLength);
    var changingTemplateY = new Int8Array(changingEntriesLength);
    var changingTemplateBit = new Uint16Array(changingEntriesLength);
    for (c = 0; c < changingEntriesLength; c++) {
      k = changingTemplateEntries[c];
      changingTemplateX[c] = template[k].x;
      changingTemplateY[c] = template[k].y;
      changingTemplateBit[c] = 1 << (templateLength - 1 - k);
    }

    // Get the safe bounding box edges from the width, height, minX, maxX, minY
    var sbb_left = -minX;
    var sbb_top = -minY;
    var sbb_right = width - maxX;

    var pseudoPixelContext = ReusedContexts[templateIndex];
    var row = new Uint8Array(width);
    var bitmap = [];

    var decoder = decodingContext.decoder;
    var contexts = decodingContext.contextCache.getContexts('GB');

    var ltp = 0, j, i0, j0, contextLabel = 0, bit, shift;
    for (var i = 0; i < height; i++) {
      if (prediction) {
        var sltp = decoder.readBit(contexts, pseudoPixelContext);
        ltp ^= sltp;
        if (ltp) {
          bitmap.push(row); // duplicate previous row
          continue;
        }
      }
      row = new Uint8Array(row);
      bitmap.push(row);
      for (j = 0; j < width; j++) {
        if (useskip && skip[i][j]) {
          row[j] = 0;
          continue;
        }
        // Are we in the middle of a scanline, so we can reuse contextLabel
        // bits?
        if (j >= sbb_left && j < sbb_right && i >= sbb_top) {
          // If yes, we can just shift the bits that are reusable and only
          // fetch the remaining ones.
          contextLabel = (contextLabel << 1) & reuseMask;
          for (k = 0; k < changingEntriesLength; k++) {
            i0 = i + changingTemplateY[k];
            j0 = j + changingTemplateX[k];
            bit = bitmap[i0][j0];
            if (bit) {
              bit = changingTemplateBit[k];
              contextLabel |= bit;
            }
          }
        } else {
          // compute the contextLabel from scratch
          contextLabel = 0;
          shift = templateLength - 1;
          for (k = 0; k < templateLength; k++, shift--) {
            j0 = j + templateX[k];
            if (j0 >= 0 && j0 < width) {
              i0 = i + templateY[k];
              if (i0 >= 0) {
                bit = bitmap[i0][j0];
                if (bit) {
                  contextLabel |= bit << shift;
                }
              }
            }
          }
        }
        var pixel = decoder.readBit(contexts, contextLabel);
        row[j] = pixel;
      }
    }
    return bitmap;
  }

  // 6.3.2 Generic Refinement Region Decoding Procedure
  function decodeRefinement(width, height, templateIndex, referenceBitmap,
                            offsetX, offsetY, prediction, at,
                            decodingContext) {
    var codingTemplate = RefinementTemplates[templateIndex].coding;
    if (templateIndex === 0) {
      codingTemplate = codingTemplate.concat([at[0]]);
    }
    var codingTemplateLength = codingTemplate.length;
    var codingTemplateX = new Int32Array(codingTemplateLength);
    var codingTemplateY = new Int32Array(codingTemplateLength);
    var k;
    for (k = 0; k < codingTemplateLength; k++) {
      codingTemplateX[k] = codingTemplate[k].x;
      codingTemplateY[k] = codingTemplate[k].y;
    }

    var referenceTemplate = RefinementTemplates[templateIndex].reference;
    if (templateIndex === 0) {
      referenceTemplate = referenceTemplate.concat([at[1]]);
    }
    var referenceTemplateLength = referenceTemplate.length;
    var referenceTemplateX = new Int32Array(referenceTemplateLength);
    var referenceTemplateY = new Int32Array(referenceTemplateLength);
    for (k = 0; k < referenceTemplateLength; k++) {
      referenceTemplateX[k] = referenceTemplate[k].x;
      referenceTemplateY[k] = referenceTemplate[k].y;
    }
    var referenceWidth = referenceBitmap[0].length;
    var referenceHeight = referenceBitmap.length;

    var pseudoPixelContext = RefinementReusedContexts[templateIndex];
    var bitmap = [];

    var decoder = decodingContext.decoder;
    var contexts = decodingContext.contextCache.getContexts('GR');

    var ltp = 0;
    for (var i = 0; i < height; i++) {
      if (prediction) {
        var sltp = decoder.readBit(contexts, pseudoPixelContext);
        ltp ^= sltp;
        if (ltp) {
          throw new Jbig2Error('prediction is not supported');
        }
      }
      var row = new Uint8Array(width);
      bitmap.push(row);
      for (var j = 0; j < width; j++) {
        var i0, j0;
        var contextLabel = 0;
        for (k = 0; k < codingTemplateLength; k++) {
          i0 = i + codingTemplateY[k];
          j0 = j + codingTemplateX[k];
          if (i0 < 0 || j0 < 0 || j0 >= width) {
            contextLabel <<= 1; // out of bound pixel
          } else {
            contextLabel = (contextLabel << 1) | bitmap[i0][j0];
          }
        }
        for (k = 0; k < referenceTemplateLength; k++) {
          i0 = i + referenceTemplateY[k] - offsetY;
          j0 = j + referenceTemplateX[k] - offsetX;
          if (i0 < 0 || i0 >= referenceHeight || j0 < 0 ||
              j0 >= referenceWidth) {
            contextLabel <<= 1; // out of bound pixel
          } else {
            contextLabel = (contextLabel << 1) | referenceBitmap[i0][j0];
          }
        }
        var pixel = decoder.readBit(contexts, contextLabel);
        row[j] = pixel;
      }
    }

    return bitmap;
  }

  // 6.5.5 Decoding the symbol dictionary
  function decodeSymbolDictionary(huffman, refinement, symbols,
                                  numberOfNewSymbols, numberOfExportedSymbols,
                                  huffmanTables, templateIndex, at,
                                  refinementTemplateIndex, refinementAt,
                                  decodingContext, huffmanInput) {
    if (huffman && refinement) {
      throw new Jbig2Error('symbol refinement with Huffman is not supported');
    }

    var newSymbols = [];
    var currentHeight = 0;
    var symbolCodeLength = log2(symbols.length + numberOfNewSymbols);

    var decoder = decodingContext.decoder;
    var contextCache = decodingContext.contextCache;
    let tableB1, symbolWidths;
    if (huffman) {
      tableB1 = getStandardTable(1); // standard table B.1
      symbolWidths = [];
      symbolCodeLength = Math.max(symbolCodeLength, 1); // 6.5.8.2.3
    }

    while (newSymbols.length < numberOfNewSymbols) {
      var deltaHeight = huffman ?
        huffmanTables.tableDeltaHeight.decode(huffmanInput) :
        decodeInteger(contextCache, 'IADH', decoder); // 6.5.6
      currentHeight += deltaHeight;
      let currentWidth = 0, totalWidth = 0;
      let firstSymbol = huffman ? symbolWidths.length : 0;
      while (true) {
        var deltaWidth = huffman ?
          huffmanTables.tableDeltaWidth.decode(huffmanInput) :
          decodeInteger(contextCache, 'IADW', decoder); // 6.5.7
        if (deltaWidth === null) {
          break; // OOB
        }
        currentWidth += deltaWidth;
        totalWidth += currentWidth;
        var bitmap;
        if (refinement) {
          // 6.5.8.2 Refinement/aggregate-coded symbol bitmap
          var numberOfInstances = decodeInteger(contextCache, 'IAAI', decoder);
          if (numberOfInstances > 1) {
            bitmap = decodeTextRegion(huffman, refinement,
                                      currentWidth, currentHeight, 0,
                                      numberOfInstances, 1, // strip size
                                      symbols.concat(newSymbols),
                                      symbolCodeLength,
                                      0, // transposed
                                      0, // ds offset
                                      1, // top left 7.4.3.1.1
                                      0, // OR operator
                                      huffmanTables,
                                      refinementTemplateIndex, refinementAt,
                                      decodingContext, 0, huffmanInput);
          } else {
            var symbolId = decodeIAID(contextCache, decoder, symbolCodeLength);
            var rdx = decodeInteger(contextCache, 'IARDX', decoder); // 6.4.11.3
            var rdy = decodeInteger(contextCache, 'IARDY', decoder); // 6.4.11.4
            var symbol = (symbolId < symbols.length ? symbols[symbolId] :
                          newSymbols[symbolId - symbols.length]);
            bitmap = decodeRefinement(currentWidth, currentHeight,
            refinementTemplateIndex, symbol, rdx, rdy, false, refinementAt,
            decodingContext);
          }
          newSymbols.push(bitmap);
        } else if (huffman) {
          // Store only symbol width and decode a collective bitmap when the
          // height class is done.
          symbolWidths.push(currentWidth);
        } else {
          // 6.5.8.1 Direct-coded symbol bitmap
          bitmap = decodeBitmap(false, currentWidth, currentHeight,
            templateIndex, false, null, at, decodingContext);
          newSymbols.push(bitmap);
        }
      }
      if (huffman && !refinement) {
        // 6.5.9 Height class collective bitmap
        let bitmapSize = huffmanTables.tableBitmapSize.decode(huffmanInput);
        huffmanInput.byteAlign();
        let collectiveBitmap;
        if (bitmapSize === 0) {
          // Uncompressed collective bitmap
          collectiveBitmap = readUncompressedBitmap(huffmanInput, totalWidth,
            currentHeight);
        } else {
          // MMR collective bitmap
          let originalEnd = huffmanInput.end;
          let bitmapEnd = huffmanInput.position + bitmapSize;
          huffmanInput.end = bitmapEnd;
          collectiveBitmap = decodeMMRBitmap(huffmanInput, totalWidth,
            currentHeight, false);
          huffmanInput.end = originalEnd;
          huffmanInput.position = bitmapEnd;
        }
        let numberOfSymbolsDecoded = symbolWidths.length;
        if (firstSymbol === numberOfSymbolsDecoded - 1) {
          // collectiveBitmap is a single symbol.
          newSymbols.push(collectiveBitmap);
        } else {
          // Divide collectiveBitmap into symbols.
          let i, y, xMin = 0, xMax, bitmapWidth, symbolBitmap;
          for (i = firstSymbol; i < numberOfSymbolsDecoded; i++) {
            bitmapWidth = symbolWidths[i];
            xMax = xMin + bitmapWidth;
            symbolBitmap = [];
            for (y = 0; y < currentHeight; y++) {
              symbolBitmap.push(collectiveBitmap[y].subarray(xMin, xMax));
            }
            newSymbols.push(symbolBitmap);
            xMin = xMax;
          }
        }
      }
    }

    // 6.5.10 Exported symbols
    var exportedSymbols = [];
    var flags = [], currentFlag = false;
    var totalSymbolsLength = symbols.length + numberOfNewSymbols;
    while (flags.length < totalSymbolsLength) {
      var runLength = huffman ? tableB1.decode(huffmanInput) :
        decodeInteger(contextCache, 'IAEX', decoder);
      while (runLength--) {
        flags.push(currentFlag);
      }
      currentFlag = !currentFlag;
    }
    for (var i = 0, ii = symbols.length; i < ii; i++) {
      if (flags[i]) {
        exportedSymbols.push(symbols[i]);
      }
    }
    for (var j = 0; j < numberOfNewSymbols; i++, j++) {
      if (flags[i]) {
        exportedSymbols.push(newSymbols[j]);
      }
    }
    return exportedSymbols;
  }

  function decodeTextRegion(huffman, refinement, width, height,
                            defaultPixelValue, numberOfSymbolInstances,
                            stripSize, inputSymbols, symbolCodeLength,
                            transposed, dsOffset, referenceCorner,
                            combinationOperator, huffmanTables,
                            refinementTemplateIndex, refinementAt,
                            decodingContext, logStripSize, huffmanInput) {
    if (huffman && refinement) {
      throw new Jbig2Error('refinement with Huffman is not supported');
    }

    // Prepare bitmap
    var bitmap = [];
    var i, row;
    for (i = 0; i < height; i++) {
      row = new Uint8Array(width);
      if (defaultPixelValue) {
        for (var j = 0; j < width; j++) {
          row[j] = defaultPixelValue;
        }
      }
      bitmap.push(row);
    }

    var decoder = decodingContext.decoder;
    var contextCache = decodingContext.contextCache;

    var stripT = huffman ? -huffmanTables.tableDeltaT.decode(huffmanInput) :
      -decodeInteger(contextCache, 'IADT', decoder); // 6.4.6
    var firstS = 0;
    i = 0;
    while (i < numberOfSymbolInstances) {
      var deltaT = huffman ? huffmanTables.tableDeltaT.decode(huffmanInput) :
        decodeInteger(contextCache, 'IADT', decoder); // 6.4.6
      stripT += deltaT;

      var deltaFirstS = huffman ?
        huffmanTables.tableFirstS.decode(huffmanInput) :
        decodeInteger(contextCache, 'IAFS', decoder); // 6.4.7
      firstS += deltaFirstS;
      var currentS = firstS;
      do {
        let currentT = 0; // 6.4.9
        if (stripSize > 1) {
          currentT = huffman ? huffmanInput.readBits(logStripSize) :
            decodeInteger(contextCache, 'IAIT', decoder);
        }
        var t = stripSize * stripT + currentT;
        var symbolId = huffman ?
          huffmanTables.symbolIDTable.decode(huffmanInput) :
          decodeIAID(contextCache, decoder, symbolCodeLength);
        var applyRefinement = (refinement && (huffman ? huffmanInput.readBit() :
          decodeInteger(contextCache, 'IARI', decoder)));
        var symbolBitmap = inputSymbols[symbolId];
        var symbolWidth = symbolBitmap[0].length;
        var symbolHeight = symbolBitmap.length;
        if (applyRefinement) {
          var rdw = decodeInteger(contextCache, 'IARDW', decoder); // 6.4.11.1
          var rdh = decodeInteger(contextCache, 'IARDH', decoder); // 6.4.11.2
          var rdx = decodeInteger(contextCache, 'IARDX', decoder); // 6.4.11.3
          var rdy = decodeInteger(contextCache, 'IARDY', decoder); // 6.4.11.4
          symbolWidth += rdw;
          symbolHeight += rdh;
          symbolBitmap = decodeRefinement(symbolWidth, symbolHeight,
            refinementTemplateIndex, symbolBitmap, (rdw >> 1) + rdx,
            (rdh >> 1) + rdy, false, refinementAt,
            decodingContext);
        }
        var offsetT = t - ((referenceCorner & 1) ? 0 : (symbolHeight - 1));
        var offsetS = currentS -
          ((referenceCorner & 2) ? (symbolWidth - 1) : 0);
        var s2, t2, symbolRow;
        if (transposed) {
          // Place Symbol Bitmap from T1,S1
          for (s2 = 0; s2 < symbolHeight; s2++) {
            row = bitmap[offsetS + s2];
            if (!row) {
              continue;
            }
            symbolRow = symbolBitmap[s2];
            // To ignore Parts of Symbol bitmap which goes
            // outside bitmap region
            var maxWidth = Math.min(width - offsetT, symbolWidth);
            switch (combinationOperator) {
              case 0: // OR
                for (t2 = 0; t2 < maxWidth; t2++) {
                  row[offsetT + t2] |= symbolRow[t2];
                }
                break;
              case 2: // XOR
                for (t2 = 0; t2 < maxWidth; t2++) {
                  row[offsetT + t2] ^= symbolRow[t2];
                }
                break;
              default:
                throw new Jbig2Error(
                  `operator ${combinationOperator} is not supported`);
            }
          }
          currentS += symbolHeight - 1;
        } else {
          for (t2 = 0; t2 < symbolHeight; t2++) {
            row = bitmap[offsetT + t2];
            if (!row) {
              continue;
            }
            symbolRow = symbolBitmap[t2];
            switch (combinationOperator) {
              case 0: // OR
                for (s2 = 0; s2 < symbolWidth; s2++) {
                  row[offsetS + s2] |= symbolRow[s2];
                }
                break;
              case 2: // XOR
                for (s2 = 0; s2 < symbolWidth; s2++) {
                  row[offsetS + s2] ^= symbolRow[s2];
                }
                break;
              default:
                throw new Jbig2Error(
                  `operator ${combinationOperator} is not supported`);
            }
          }
          currentS += symbolWidth - 1;
        }
        i++;
        var deltaS = huffman ? huffmanTables.tableDeltaS.decode(huffmanInput) :
          decodeInteger(contextCache, 'IADS', decoder); // 6.4.8
        if (deltaS === null) {
          break; // OOB
        }
        currentS += deltaS + dsOffset;
      } while (true);
    }
    return bitmap;
  }

  function decodePatternDictionary(mmr, patternWidth, patternHeight,
                                   maxPatternIndex, template, decodingContext) {
    let at = [];
    if (!mmr) {
      at.push({
        x: -patternWidth,
        y: 0,
      });
      if (template === 0) {
        at.push({
          x: -3,
          y: -1,
        });
        at.push({
          x: 2,
          y: -2,
        });
        at.push({
          x: -2,
          y: -2,
        });
      }
    }
    let collectiveWidth = (maxPatternIndex + 1) * patternWidth;
    let collectiveBitmap = decodeBitmap(mmr, collectiveWidth, patternHeight,
                                        template, false, null, at,
                                        decodingContext);
    // Divide collective bitmap into patterns.
    let patterns = [], i = 0, patternBitmap, xMin, xMax, y;
    while (i <= maxPatternIndex) {
      patternBitmap = [];
      xMin = patternWidth * i;
      xMax = xMin + patternWidth;
      for (y = 0; y < patternHeight; y++) {
        patternBitmap.push(collectiveBitmap[y].subarray(xMin, xMax));
      }
      patterns.push(patternBitmap);
      i++;
    }
    return patterns;
  }

  function decodeHalftoneRegion(mmr, patterns, template, regionWidth,
                                regionHeight, defaultPixelValue, enableSkip,
                                combinationOperator, gridWidth, gridHeight,
                                gridOffsetX, gridOffsetY, gridVectorX,
                                gridVectorY, decodingContext) {
    let skip = null;
    if (enableSkip) {
      throw new Jbig2Error('skip is not supported');
    }
    if (combinationOperator !== 0) {
      throw new Jbig2Error('operator ' + combinationOperator +
        ' is not supported in halftone region');
    }

    // Prepare bitmap.
    let regionBitmap = [];
    let i, j, row;
    for (i = 0; i < regionHeight; i++) {
      row = new Uint8Array(regionWidth);
      if (defaultPixelValue) {
        for (j = 0; j < regionWidth; j++) {
          row[j] = defaultPixelValue;
        }
      }
      regionBitmap.push(row);
    }

    let numberOfPatterns = patterns.length;
    let pattern0 = patterns[0];
    let patternWidth = pattern0[0].length, patternHeight = pattern0.length;
    let bitsPerValue = log2(numberOfPatterns);
    let at = [];
    if (!mmr) {
      at.push({
        x: (template <= 1) ? 3 : 2,
        y: -1,
      });
      if (template === 0) {
        at.push({
          x: -3,
          y: -1,
        });
        at.push({
          x: 2,
          y: -2,
        });
        at.push({
          x: -2,
          y: -2,
        });
      }
    }
    // Annex C. Gray-scale Image Decoding Procedure.
    let grayScaleBitPlanes = [], mmrInput, bitmap;
    if (mmr) {
      // MMR bit planes are in one continuous stream. Only EOFB codes indicate
      // the end of each bitmap, so EOFBs must be decoded.
      mmrInput = new Reader(decodingContext.data, decodingContext.start,
        decodingContext.end);
    }
    for (i = bitsPerValue - 1; i >= 0; i--) {
      if (mmr) {
        bitmap = decodeMMRBitmap(mmrInput, gridWidth, gridHeight, true);
      } else {
        bitmap = decodeBitmap(false, gridWidth, gridHeight, template, false,
          skip, at, decodingContext);
      }
      grayScaleBitPlanes[i] = bitmap;
    }
    // 6.6.5.2 Rendering the patterns.
    let mg, ng, bit, patternIndex, patternBitmap, x, y, patternRow, regionRow;
    for (mg = 0; mg < gridHeight; mg++) {
      for (ng = 0; ng < gridWidth; ng++) {
        bit = 0;
        patternIndex = 0;
        for (j = bitsPerValue - 1; j >= 0; j--) {
          bit = grayScaleBitPlanes[j][mg][ng] ^ bit; // Gray decoding
          patternIndex |= bit << j;
        }
        patternBitmap = patterns[patternIndex];
        x = (gridOffsetX + mg * gridVectorY + ng * gridVectorX) >> 8;
        y = (gridOffsetY + mg * gridVectorX - ng * gridVectorY) >> 8;
        // Draw patternBitmap at (x, y).
        if (x >= 0 && x + patternWidth <= regionWidth && y >= 0 &&
            y + patternHeight <= regionHeight) {
          for (i = 0; i < patternHeight; i++) {
            regionRow = regionBitmap[y + i];
            patternRow = patternBitmap[i];
            for (j = 0; j < patternWidth; j++) {
              regionRow[x + j] |= patternRow[j];
            }
          }
        } else {
          let regionX, regionY;
          for (i = 0; i < patternHeight; i++) {
            regionY = y + i;
            if (regionY < 0 || regionY >= regionHeight) {
              continue;
            }
            regionRow = regionBitmap[regionY];
            patternRow = patternBitmap[i];
            for (j = 0; j < patternWidth; j++) {
              regionX = x + j;
              if (regionX >= 0 && regionX < regionWidth) {
                regionRow[regionX] |= patternRow[j];
              }
            }
          }
        }
      }
    }
    return regionBitmap;
  }

  function readSegmentHeader(data, start) {
    var segmentHeader = {};
    segmentHeader.number = readUint32(data, start);
    var flags = data[start + 4];
    var segmentType = flags & 0x3F;
    if (!SegmentTypes[segmentType]) {
      throw new Jbig2Error('invalid segment type: ' + segmentType);
    }
    segmentHeader.type = segmentType;
    segmentHeader.typeName = SegmentTypes[segmentType];
    segmentHeader.deferredNonRetain = !!(flags & 0x80);

    var pageAssociationFieldSize = !!(flags & 0x40);
    var referredFlags = data[start + 5];
    var referredToCount = (referredFlags >> 5) & 7;
    var retainBits = [referredFlags & 31];
    var position = start + 6;
    if (referredFlags === 7) {
      referredToCount = readUint32(data, position - 1) & 0x1FFFFFFF;
      position += 3;
      var bytes = (referredToCount + 7) >> 3;
      retainBits[0] = data[position++];
      while (--bytes > 0) {
        retainBits.push(data[position++]);
      }
    } else if (referredFlags === 5 || referredFlags === 6) {
      throw new Jbig2Error('invalid referred-to flags');
    }

    segmentHeader.retainBits = retainBits;
    var referredToSegmentNumberSize = (segmentHeader.number <= 256 ? 1 :
      (segmentHeader.number <= 65536 ? 2 : 4));
    var referredTo = [];
    var i, ii;
    for (i = 0; i < referredToCount; i++) {
      var number = (referredToSegmentNumberSize === 1 ? data[position] :
        (referredToSegmentNumberSize === 2 ? readUint16(data, position) :
        readUint32(data, position)));
      referredTo.push(number);
      position += referredToSegmentNumberSize;
    }
    segmentHeader.referredTo = referredTo;
    if (!pageAssociationFieldSize) {
      segmentHeader.pageAssociation = data[position++];
    } else {
      segmentHeader.pageAssociation = readUint32(data, position);
      position += 4;
    }
    segmentHeader.length = readUint32(data, position);
    position += 4;

    if (segmentHeader.length === 0xFFFFFFFF) {
      // 7.2.7 Segment data length, unknown segment length
      if (segmentType === 38) { // ImmediateGenericRegion
        var genericRegionInfo = readRegionSegmentInformation(data, position);
        var genericRegionSegmentFlags = data[position +
          RegionSegmentInformationFieldLength];
        var genericRegionMmr = !!(genericRegionSegmentFlags & 1);
        // searching for the segment end
        var searchPatternLength = 6;
        var searchPattern = new Uint8Array(searchPatternLength);
        if (!genericRegionMmr) {
          searchPattern[0] = 0xFF;
          searchPattern[1] = 0xAC;
        }
        searchPattern[2] = (genericRegionInfo.height >>> 24) & 0xFF;
        searchPattern[3] = (genericRegionInfo.height >> 16) & 0xFF;
        searchPattern[4] = (genericRegionInfo.height >> 8) & 0xFF;
        searchPattern[5] = genericRegionInfo.height & 0xFF;
        for (i = position, ii = data.length; i < ii; i++) {
          var j = 0;
          while (j < searchPatternLength && searchPattern[j] === data[i + j]) {
            j++;
          }
          if (j === searchPatternLength) {
            segmentHeader.length = i + searchPatternLength;
            break;
          }
        }
        if (segmentHeader.length === 0xFFFFFFFF) {
          throw new Jbig2Error('segment end was not found');
        }
      } else {
        throw new Jbig2Error('invalid unknown segment length');
      }
    }
    segmentHeader.headerEnd = position;
    return segmentHeader;
  }

  function readSegments(header, data, start, end) {
    var segments = [];
    var position = start;
    while (position < end) {
      var segmentHeader = readSegmentHeader(data, position);
      position = segmentHeader.headerEnd;
      var segment = {
        header: segmentHeader,
        data,
      };
      if (!header.randomAccess) {
        segment.start = position;
        position += segmentHeader.length;
        segment.end = position;
      }
      segments.push(segment);
      if (segmentHeader.type === 51) {
        break; // end of file is found
      }
    }
    if (header.randomAccess) {
      for (var i = 0, ii = segments.length; i < ii; i++) {
        segments[i].start = position;
        position += segments[i].header.length;
        segments[i].end = position;
      }
    }
    return segments;
  }

  // 7.4.1 Region segment information field
  function readRegionSegmentInformation(data, start) {
    return {
      width: readUint32(data, start),
      height: readUint32(data, start + 4),
      x: readUint32(data, start + 8),
      y: readUint32(data, start + 12),
      combinationOperator: data[start + 16] & 7,
    };
  }
  var RegionSegmentInformationFieldLength = 17;

  function processSegment(segment, visitor) {
    var header = segment.header;

    var data = segment.data, position = segment.start, end = segment.end;
    var args, at, i, atLength;
    switch (header.type) {
      case 0: // SymbolDictionary
        // 7.4.2 Symbol dictionary segment syntax
        var dictionary = {};
        var dictionaryFlags = readUint16(data, position); // 7.4.2.1.1
        dictionary.huffman = !!(dictionaryFlags & 1);
        dictionary.refinement = !!(dictionaryFlags & 2);
        dictionary.huffmanDHSelector = (dictionaryFlags >> 2) & 3;
        dictionary.huffmanDWSelector = (dictionaryFlags >> 4) & 3;
        dictionary.bitmapSizeSelector = (dictionaryFlags >> 6) & 1;
        dictionary.aggregationInstancesSelector = (dictionaryFlags >> 7) & 1;
        dictionary.bitmapCodingContextUsed = !!(dictionaryFlags & 256);
        dictionary.bitmapCodingContextRetained = !!(dictionaryFlags & 512);
        dictionary.template = (dictionaryFlags >> 10) & 3;
        dictionary.refinementTemplate = (dictionaryFlags >> 12) & 1;
        position += 2;
        if (!dictionary.huffman) {
          atLength = dictionary.template === 0 ? 4 : 1;
          at = [];
          for (i = 0; i < atLength; i++) {
            at.push({
              x: readInt8(data, position),
              y: readInt8(data, position + 1),
            });
            position += 2;
          }
          dictionary.at = at;
        }
        if (dictionary.refinement && !dictionary.refinementTemplate) {
          at = [];
          for (i = 0; i < 2; i++) {
            at.push({
              x: readInt8(data, position),
              y: readInt8(data, position + 1),
            });
            position += 2;
          }
          dictionary.refinementAt = at;
        }
        dictionary.numberOfExportedSymbols = readUint32(data, position);
        position += 4;
        dictionary.numberOfNewSymbols = readUint32(data, position);
        position += 4;
        args = [dictionary, header.number, header.referredTo,
                data, position, end];
        break;
      case 6: // ImmediateTextRegion
      case 7: // ImmediateLosslessTextRegion
        var textRegion = {};
        textRegion.info = readRegionSegmentInformation(data, position);
        position += RegionSegmentInformationFieldLength;
        var textRegionSegmentFlags = readUint16(data, position);
        position += 2;
        textRegion.huffman = !!(textRegionSegmentFlags & 1);
        textRegion.refinement = !!(textRegionSegmentFlags & 2);
        textRegion.logStripSize = (textRegionSegmentFlags >> 2) & 3;
        textRegion.stripSize = 1 << textRegion.logStripSize;
        textRegion.referenceCorner = (textRegionSegmentFlags >> 4) & 3;
        textRegion.transposed = !!(textRegionSegmentFlags & 64);
        textRegion.combinationOperator = (textRegionSegmentFlags >> 7) & 3;
        textRegion.defaultPixelValue = (textRegionSegmentFlags >> 9) & 1;
        textRegion.dsOffset = (textRegionSegmentFlags << 17) >> 27;
        textRegion.refinementTemplate = (textRegionSegmentFlags >> 15) & 1;
        if (textRegion.huffman) {
          var textRegionHuffmanFlags = readUint16(data, position);
          position += 2;
          textRegion.huffmanFS = (textRegionHuffmanFlags) & 3;
          textRegion.huffmanDS = (textRegionHuffmanFlags >> 2) & 3;
          textRegion.huffmanDT = (textRegionHuffmanFlags >> 4) & 3;
          textRegion.huffmanRefinementDW = (textRegionHuffmanFlags >> 6) & 3;
          textRegion.huffmanRefinementDH = (textRegionHuffmanFlags >> 8) & 3;
          textRegion.huffmanRefinementDX = (textRegionHuffmanFlags >> 10) & 3;
          textRegion.huffmanRefinementDY = (textRegionHuffmanFlags >> 12) & 3;
          textRegion.huffmanRefinementSizeSelector =
            !!(textRegionHuffmanFlags & 0x4000);
        }
        if (textRegion.refinement && !textRegion.refinementTemplate) {
          at = [];
          for (i = 0; i < 2; i++) {
            at.push({
              x: readInt8(data, position),
              y: readInt8(data, position + 1),
            });
            position += 2;
          }
          textRegion.refinementAt = at;
        }
        textRegion.numberOfSymbolInstances = readUint32(data, position);
        position += 4;
        args = [textRegion, header.referredTo, data, position, end];
        break;
      case 16: // PatternDictionary
        // 7.4.4. Pattern dictionary segment syntax
        let patternDictionary = {};
        let patternDictionaryFlags = data[position++];
        patternDictionary.mmr = !!(patternDictionaryFlags & 1);
        patternDictionary.template = (patternDictionaryFlags >> 1) & 3;
        patternDictionary.patternWidth = data[position++];
        patternDictionary.patternHeight = data[position++];
        patternDictionary.maxPatternIndex = readUint32(data, position);
        position += 4;
        args = [patternDictionary, header.number, data, position, end];
        break;
      case 22: // ImmediateHalftoneRegion
      case 23: // ImmediateLosslessHalftoneRegion
        // 7.4.5 Halftone region segment syntax
        let halftoneRegion = {};
        halftoneRegion.info = readRegionSegmentInformation(data, position);
        position += RegionSegmentInformationFieldLength;
        let halftoneRegionFlags = data[position++];
        halftoneRegion.mmr = !!(halftoneRegionFlags & 1);
        halftoneRegion.template = (halftoneRegionFlags >> 1) & 3;
        halftoneRegion.enableSkip = !!(halftoneRegionFlags & 8);
        halftoneRegion.combinationOperator = (halftoneRegionFlags >> 4) & 7;
        halftoneRegion.defaultPixelValue = (halftoneRegionFlags >> 7) & 1;
        halftoneRegion.gridWidth = readUint32(data, position);
        position += 4;
        halftoneRegion.gridHeight = readUint32(data, position);
        position += 4;
        halftoneRegion.gridOffsetX = readUint32(data, position) & 0xFFFFFFFF;
        position += 4;
        halftoneRegion.gridOffsetY = readUint32(data, position) & 0xFFFFFFFF;
        position += 4;
        halftoneRegion.gridVectorX = readUint16(data, position);
        position += 2;
        halftoneRegion.gridVectorY = readUint16(data, position);
        position += 2;
        args = [halftoneRegion, header.referredTo, data, position, end];
        break;
      case 38: // ImmediateGenericRegion
      case 39: // ImmediateLosslessGenericRegion
        var genericRegion = {};
        genericRegion.info = readRegionSegmentInformation(data, position);
        position += RegionSegmentInformationFieldLength;
        var genericRegionSegmentFlags = data[position++];
        genericRegion.mmr = !!(genericRegionSegmentFlags & 1);
        genericRegion.template = (genericRegionSegmentFlags >> 1) & 3;
        genericRegion.prediction = !!(genericRegionSegmentFlags & 8);
        if (!genericRegion.mmr) {
          atLength = genericRegion.template === 0 ? 4 : 1;
          at = [];
          for (i = 0; i < atLength; i++) {
            at.push({
              x: readInt8(data, position),
              y: readInt8(data, position + 1),
            });
            position += 2;
          }
          genericRegion.at = at;
        }
        args = [genericRegion, data, position, end];
        break;
      case 48: // PageInformation
        var pageInfo = {
          width: readUint32(data, position),
          height: readUint32(data, position + 4),
          resolutionX: readUint32(data, position + 8),
          resolutionY: readUint32(data, position + 12),
        };
        if (pageInfo.height === 0xFFFFFFFF) {
          delete pageInfo.height;
        }
        var pageSegmentFlags = data[position + 16];
        readUint16(data, position + 17); // pageStripingInformation
        pageInfo.lossless = !!(pageSegmentFlags & 1);
        pageInfo.refinement = !!(pageSegmentFlags & 2);
        pageInfo.defaultPixelValue = (pageSegmentFlags >> 2) & 1;
        pageInfo.combinationOperator = (pageSegmentFlags >> 3) & 3;
        pageInfo.requiresBuffer = !!(pageSegmentFlags & 32);
        pageInfo.combinationOperatorOverride = !!(pageSegmentFlags & 64);
        args = [pageInfo];
        break;
      case 49: // EndOfPage
        break;
      case 50: // EndOfStripe
        break;
      case 51: // EndOfFile
        break;
      case 53: // Tables
        args = [header.number, data, position, end];
        break;
      case 62: // 7.4.15 defines 2 extension types which
               // are comments and can be ignored.
        break;
      default:
        throw new Jbig2Error(`segment type ${header.typeName}(${header.type})` +
                             ' is not implemented');
    }
    var callbackName = 'on' + header.typeName;
    if (callbackName in visitor) {
      visitor[callbackName].apply(visitor, args);
    }
  }

  function processSegments(segments, visitor) {
    for (var i = 0, ii = segments.length; i < ii; i++) {
      processSegment(segments[i], visitor);
    }
  }

  function parseJbig2Chunks(chunks) {
    var visitor = new SimpleSegmentVisitor();
    for (var i = 0, ii = chunks.length; i < ii; i++) {
      var chunk = chunks[i];
      var segments = readSegments({}, chunk.data, chunk.start, chunk.end);
      processSegments(segments, visitor);
    }
    return visitor.buffer;
  }

  function parseJbig2(data) {
    let position = 0, end = data.length;

    if (data[position] !== 0x97 || data[position + 1] !== 0x4A ||
        data[position + 2] !== 0x42 || data[position + 3] !== 0x32 ||
        data[position + 4] !== 0x0D || data[position + 5] !== 0x0A ||
        data[position + 6] !== 0x1A || data[position + 7] !== 0x0A) {
      throw new Jbig2Error('parseJbig2 - invalid header.');
    }

    let header = Object.create(null);
    position += 8;
    const flags = data[position++];
    header.randomAccess = !(flags & 1);
    if (!(flags & 2)) {
      header.numberOfPages = readUint32(data, position);
      position += 4;
    }

    let segments = readSegments(header, data, position, end);
    let visitor = new SimpleSegmentVisitor();
    processSegments(segments, visitor);

    const { width, height, } = visitor.currentPageInfo;
    const bitPacked = visitor.buffer;
    let imgData = new Uint8ClampedArray(width * height);
    let q = 0, k = 0;
    for (let i = 0; i < height; i++) {
      let mask = 0, buffer;
      for (let j = 0; j < width; j++) {
        if (!mask) {
          mask = 128; buffer = bitPacked[k++];
        }
        imgData[q++] = (buffer & mask) ? 0 : 255;
        mask >>= 1;
      }
    }

    return { imgData, width, height, };
  }

  function SimpleSegmentVisitor() {}

  SimpleSegmentVisitor.prototype = {
    onPageInformation: function SimpleSegmentVisitor_onPageInformation(info) {
      this.currentPageInfo = info;
      var rowSize = (info.width + 7) >> 3;
      var buffer = new Uint8ClampedArray(rowSize * info.height);
      // The contents of ArrayBuffers are initialized to 0.
      // Fill the buffer with 0xFF only if info.defaultPixelValue is set
      if (info.defaultPixelValue) {
        for (var i = 0, ii = buffer.length; i < ii; i++) {
          buffer[i] = 0xFF;
        }
      }
      this.buffer = buffer;
    },
    drawBitmap: function SimpleSegmentVisitor_drawBitmap(regionInfo, bitmap) {
      var pageInfo = this.currentPageInfo;
      var width = regionInfo.width, height = regionInfo.height;
      var rowSize = (pageInfo.width + 7) >> 3;
      var combinationOperator = pageInfo.combinationOperatorOverride ?
        regionInfo.combinationOperator : pageInfo.combinationOperator;
      var buffer = this.buffer;
      var mask0 = 128 >> (regionInfo.x & 7);
      var offset0 = regionInfo.y * rowSize + (regionInfo.x >> 3);
      var i, j, mask, offset;
      switch (combinationOperator) {
        case 0: // OR
          for (i = 0; i < height; i++) {
            mask = mask0;
            offset = offset0;
            for (j = 0; j < width; j++) {
              if (bitmap[i][j]) {
                buffer[offset] |= mask;
              }
              mask >>= 1;
              if (!mask) {
                mask = 128;
                offset++;
              }
            }
            offset0 += rowSize;
          }
        break;
        case 2: // XOR
          for (i = 0; i < height; i++) {
            mask = mask0;
            offset = offset0;
            for (j = 0; j < width; j++) {
              if (bitmap[i][j]) {
                buffer[offset] ^= mask;
              }
              mask >>= 1;
              if (!mask) {
                mask = 128;
                offset++;
              }
            }
            offset0 += rowSize;
          }
          break;
        default:
          throw new Jbig2Error(
            `operator ${combinationOperator} is not supported`);
      }
    },
    onImmediateGenericRegion:
      function SimpleSegmentVisitor_onImmediateGenericRegion(region, data,
                                                             start, end) {
      var regionInfo = region.info;
      var decodingContext = new DecodingContext(data, start, end);
      var bitmap = decodeBitmap(region.mmr, regionInfo.width, regionInfo.height,
                                region.template, region.prediction, null,
                                region.at, decodingContext);
      this.drawBitmap(regionInfo, bitmap);
    },
    onImmediateLosslessGenericRegion:
      function SimpleSegmentVisitor_onImmediateLosslessGenericRegion() {
      this.onImmediateGenericRegion.apply(this, arguments);
    },
    onSymbolDictionary:
      function SimpleSegmentVisitor_onSymbolDictionary(dictionary,
                                                       currentSegment,
                                                       referredSegments,
                                                       data, start, end) {
      let huffmanTables, huffmanInput;
      if (dictionary.huffman) {
        huffmanTables = getSymbolDictionaryHuffmanTables(dictionary,
          referredSegments, this.customTables);
        huffmanInput = new Reader(data, start, end);
      }

      // Combines exported symbols from all referred segments
      var symbols = this.symbols;
      if (!symbols) {
        this.symbols = symbols = {};
      }

      var inputSymbols = [];
      for (var i = 0, ii = referredSegments.length; i < ii; i++) {
        let referredSymbols = symbols[referredSegments[i]];
        // referredSymbols is undefined when we have a reference to a Tables
        // segment instead of a SymbolDictionary.
        if (referredSymbols) {
          inputSymbols = inputSymbols.concat(referredSymbols);
        }
      }

      var decodingContext = new DecodingContext(data, start, end);
      symbols[currentSegment] = decodeSymbolDictionary(dictionary.huffman,
        dictionary.refinement, inputSymbols, dictionary.numberOfNewSymbols,
        dictionary.numberOfExportedSymbols, huffmanTables,
        dictionary.template, dictionary.at,
        dictionary.refinementTemplate, dictionary.refinementAt,
        decodingContext, huffmanInput);
    },
    onImmediateTextRegion:
      function SimpleSegmentVisitor_onImmediateTextRegion(region,
                                                          referredSegments,
                                                          data, start, end) {
      var regionInfo = region.info;
      let huffmanTables, huffmanInput;

      // Combines exported symbols from all referred segments
      var symbols = this.symbols;
      var inputSymbols = [];
      for (var i = 0, ii = referredSegments.length; i < ii; i++) {
        let referredSymbols = symbols[referredSegments[i]];
        // referredSymbols is undefined when we have a reference to a Tables
        // segment instead of a SymbolDictionary.
        if (referredSymbols) {
          inputSymbols = inputSymbols.concat(referredSymbols);
        }
      }
      var symbolCodeLength = log2(inputSymbols.length);
      if (region.huffman) {
        huffmanInput = new Reader(data, start, end);
        huffmanTables = getTextRegionHuffmanTables(region, referredSegments,
          this.customTables, inputSymbols.length, huffmanInput);
      }

      var decodingContext = new DecodingContext(data, start, end);
      var bitmap = decodeTextRegion(region.huffman, region.refinement,
        regionInfo.width, regionInfo.height, region.defaultPixelValue,
        region.numberOfSymbolInstances, region.stripSize, inputSymbols,
        symbolCodeLength, region.transposed, region.dsOffset,
        region.referenceCorner, region.combinationOperator, huffmanTables,
        region.refinementTemplate, region.refinementAt, decodingContext,
        region.logStripSize, huffmanInput);
      this.drawBitmap(regionInfo, bitmap);
    },
    onImmediateLosslessTextRegion:
      function SimpleSegmentVisitor_onImmediateLosslessTextRegion() {
      this.onImmediateTextRegion.apply(this, arguments);
    },
    onPatternDictionary(dictionary, currentSegment, data, start, end) {
      let patterns = this.patterns;
      if (!patterns) {
        this.patterns = patterns = {};
      }
      let decodingContext = new DecodingContext(data, start, end);
      patterns[currentSegment] = decodePatternDictionary(dictionary.mmr,
        dictionary.patternWidth, dictionary.patternHeight,
        dictionary.maxPatternIndex, dictionary.template, decodingContext);
    },
    onImmediateHalftoneRegion(region, referredSegments, data, start, end) {
      // HalftoneRegion refers to exactly one PatternDictionary.
      let patterns = this.patterns[referredSegments[0]];
      let regionInfo = region.info;
      let decodingContext = new DecodingContext(data, start, end);
      let bitmap = decodeHalftoneRegion(region.mmr, patterns,
        region.template, regionInfo.width, regionInfo.height,
        region.defaultPixelValue, region.enableSkip, region.combinationOperator,
        region.gridWidth, region.gridHeight, region.gridOffsetX,
        region.gridOffsetY, region.gridVectorX, region.gridVectorY,
        decodingContext);
      this.drawBitmap(regionInfo, bitmap);
    },
    onImmediateLosslessHalftoneRegion() {
      this.onImmediateHalftoneRegion.apply(this, arguments);
    },
    onTables(currentSegment, data, start, end) {
      let customTables = this.customTables;
      if (!customTables) {
        this.customTables = customTables = {};
      }
      customTables[currentSegment] = decodeTablesSegment(data, start, end);
    },
  };

  function HuffmanLine(lineData) {
    if (lineData.length === 2) {
      // OOB line.
      this.isOOB = true;
      this.rangeLow = 0;
      this.prefixLength = lineData[0];
      this.rangeLength = 0;
      this.prefixCode = lineData[1];
      this.isLowerRange = false;
    } else {
      // Normal, upper range or lower range line.
      // Upper range lines are processed like normal lines.
      this.isOOB = false;
      this.rangeLow = lineData[0];
      this.prefixLength = lineData[1];
      this.rangeLength = lineData[2];
      this.prefixCode = lineData[3];
      this.isLowerRange = (lineData[4] === 'lower');
    }
  }

  function HuffmanTreeNode(line) {
    this.children = [];
    if (line) {
      // Leaf node
      this.isLeaf = true;
      this.rangeLength = line.rangeLength;
      this.rangeLow = line.rangeLow;
      this.isLowerRange = line.isLowerRange;
      this.isOOB = line.isOOB;
    } else {
      // Intermediate or root node
      this.isLeaf = false;
    }
  }

  HuffmanTreeNode.prototype = {
    buildTree(line, shift) {
      let bit = (line.prefixCode >> shift) & 1;
      if (shift <= 0) {
        // Create a leaf node.
        this.children[bit] = new HuffmanTreeNode(line);
      } else {
        // Create an intermediate node and continue recursively.
        let node = this.children[bit];
        if (!node) {
          this.children[bit] = node = new HuffmanTreeNode(null);
        }
        node.buildTree(line, shift - 1);
      }
    },
    decodeNode(reader) {
      if (this.isLeaf) {
        if (this.isOOB) {
          return null;
        }
        let htOffset = reader.readBits(this.rangeLength);
        return this.rangeLow + (this.isLowerRange ? -htOffset : htOffset);
      }
      let node = this.children[reader.readBit()];
      if (!node) {
        throw new Jbig2Error('invalid Huffman data');
      }
      return node.decodeNode(reader);
    },
  };

  function HuffmanTable(lines, prefixCodesDone) {
    if (!prefixCodesDone) {
      this.assignPrefixCodes(lines);
    }
    // Create Huffman tree.
    this.rootNode = new HuffmanTreeNode(null);
    let i, ii = lines.length, line;
    for (i = 0; i < ii; i++) {
      line = lines[i];
      if (line.prefixLength > 0) {
        this.rootNode.buildTree(line, line.prefixLength - 1);
      }
    }
  }

  HuffmanTable.prototype = {
    decode(reader) {
      return this.rootNode.decodeNode(reader);
    },
    assignPrefixCodes(lines) {
      // Annex B.3 Assigning the prefix codes.
      let linesLength = lines.length, prefixLengthMax = 0, i;
      for (i = 0; i < linesLength; i++) {
        prefixLengthMax = Math.max(prefixLengthMax, lines[i].prefixLength);
      }

      let histogram = new Uint32Array(prefixLengthMax + 1);
      for (i = 0; i < linesLength; i++) {
        histogram[lines[i].prefixLength]++;
      }
      let currentLength = 1, firstCode = 0, currentCode, currentTemp, line;
      histogram[0] = 0;

      while (currentLength <= prefixLengthMax) {
        firstCode = (firstCode + histogram[currentLength - 1]) << 1;
        currentCode = firstCode;
        currentTemp = 0;
        while (currentTemp < linesLength) {
          line = lines[currentTemp];
          if (line.prefixLength === currentLength) {
            line.prefixCode = currentCode;
            currentCode++;
          }
          currentTemp++;
        }
        currentLength++;
      }
    },
  };

  function decodeTablesSegment(data, start, end) {
    // Decodes a Tables segment, i.e., a custom Huffman table.
    // Annex B.2 Code table structure.
    let flags = data[start];
    let lowestValue = readUint32(data, start + 1) & 0xFFFFFFFF;
    let highestValue = readUint32(data, start + 5) & 0xFFFFFFFF;
    let reader = new Reader(data, start + 9, end);

    let prefixSizeBits = ((flags >> 1) & 7) + 1;
    let rangeSizeBits = ((flags >> 4) & 7) + 1;
    let lines = [];
    let prefixLength, rangeLength, currentRangeLow = lowestValue;

    // Normal table lines
    do {
      prefixLength = reader.readBits(prefixSizeBits);
      rangeLength = reader.readBits(rangeSizeBits);
      lines.push(new HuffmanLine(
        [currentRangeLow, prefixLength, rangeLength, 0]));
      currentRangeLow += 1 << rangeLength;
    } while (currentRangeLow < highestValue);

    // Lower range table line
    prefixLength = reader.readBits(prefixSizeBits);
    lines.push(
      new HuffmanLine([lowestValue - 1, prefixLength, 32, 0, 'lower']));

    // Upper range table line
    prefixLength = reader.readBits(prefixSizeBits);
    lines.push(new HuffmanLine([highestValue, prefixLength, 32, 0]));

    if (flags & 1) {
      // Out-of-band table line
      prefixLength = reader.readBits(prefixSizeBits);
      lines.push(new HuffmanLine([prefixLength, 0]));
    }

    return new HuffmanTable(lines, false);
  }

  let standardTablesCache = {};

  function getStandardTable(number) {
    // Annex B.5 Standard Huffman tables.
    let table = standardTablesCache[number];
    if (table) {
      return table;
    }
    let lines;
    switch (number) {
      case 1:
        lines = [
          [0, 1, 4, 0x0],
          [16, 2, 8, 0x2],
          [272, 3, 16, 0x6],
          [65808, 3, 32, 0x7] // upper
        ];
        break;
      case 2:
        lines = [
          [0, 1, 0, 0x0],
          [1, 2, 0, 0x2],
          [2, 3, 0, 0x6],
          [3, 4, 3, 0xE],
          [11, 5, 6, 0x1E],
          [75, 6, 32, 0x3E], // upper
          [6, 0x3F] // OOB
        ];
        break;
      case 3:
        lines = [
          [-256, 8, 8, 0xFE],
          [0, 1, 0, 0x0],
          [1, 2, 0, 0x2],
          [2, 3, 0, 0x6],
          [3, 4, 3, 0xE],
          [11, 5, 6, 0x1E],
          [-257, 8, 32, 0xFF, 'lower'],
          [75, 7, 32, 0x7E], // upper
          [6, 0x3E] // OOB
        ];
        break;
      case 4:
        lines = [
          [1, 1, 0, 0x0],
          [2, 2, 0, 0x2],
          [3, 3, 0, 0x6],
          [4, 4, 3, 0xE],
          [12, 5, 6, 0x1E],
          [76, 5, 32, 0x1F] // upper
        ];
        break;
      case 5:
        lines = [
          [-255, 7, 8, 0x7E],
          [1, 1, 0, 0x0],
          [2, 2, 0, 0x2],
          [3, 3, 0, 0x6],
          [4, 4, 3, 0xE],
          [12, 5, 6, 0x1E],
          [-256, 7, 32, 0x7F, 'lower'],
          [76, 6, 32, 0x3E] // upper
        ];
        break;
      case 6:
        lines = [
          [-2048, 5, 10, 0x1C],
          [-1024, 4, 9, 0x8],
          [-512, 4, 8, 0x9],
          [-256, 4, 7, 0xA],
          [-128, 5, 6, 0x1D],
          [-64, 5, 5, 0x1E],
          [-32, 4, 5, 0xB],
          [0, 2, 7, 0x0],
          [128, 3, 7, 0x2],
          [256, 3, 8, 0x3],
          [512, 4, 9, 0xC],
          [1024, 4, 10, 0xD],
          [-2049, 6, 32, 0x3E, 'lower'],
          [2048, 6, 32, 0x3F] // upper
        ];
        break;
      case 7:
        lines = [
          [-1024, 4, 9, 0x8],
          [-512, 3, 8, 0x0],
          [-256, 4, 7, 0x9],
          [-128, 5, 6, 0x1A],
          [-64, 5, 5, 0x1B],
          [-32, 4, 5, 0xA],
          [0, 4, 5, 0xB],
          [32, 5, 5, 0x1C],
          [64, 5, 6, 0x1D],
          [128, 4, 7, 0xC],
          [256, 3, 8, 0x1],
          [512, 3, 9, 0x2],
          [1024, 3, 10, 0x3],
          [-1025, 5, 32, 0x1E, 'lower'],
          [2048, 5, 32, 0x1F] // upper
        ];
        break;
      case 8:
        lines = [
          [-15, 8, 3, 0xFC],
          [-7, 9, 1, 0x1FC],
          [-5, 8, 1, 0xFD],
          [-3, 9, 0, 0x1FD],
          [-2, 7, 0, 0x7C],
          [-1, 4, 0, 0xA],
          [0, 2, 1, 0x0],
          [2, 5, 0, 0x1A],
          [3, 6, 0, 0x3A],
          [4, 3, 4, 0x4],
          [20, 6, 1, 0x3B],
          [22, 4, 4, 0xB],
          [38, 4, 5, 0xC],
          [70, 5, 6, 0x1B],
          [134, 5, 7, 0x1C],
          [262, 6, 7, 0x3C],
          [390, 7, 8, 0x7D],
          [646, 6, 10, 0x3D],
          [-16, 9, 32, 0x1FE, 'lower'],
          [1670, 9, 32, 0x1FF], // upper
          [2, 0x1] // OOB
        ];
        break;
      case 9:
        lines = [
          [-31, 8, 4, 0xFC],
          [-15, 9, 2, 0x1FC],
          [-11, 8, 2, 0xFD],
          [-7, 9, 1, 0x1FD],
          [-5, 7, 1, 0x7C],
          [-3, 4, 1, 0xA],
          [-1, 3, 1, 0x2],
          [1, 3, 1, 0x3],
          [3, 5, 1, 0x1A],
          [5, 6, 1, 0x3A],
          [7, 3, 5, 0x4],
          [39, 6, 2, 0x3B],
          [43, 4, 5, 0xB],
          [75, 4, 6, 0xC],
          [139, 5, 7, 0x1B],
          [267, 5, 8, 0x1C],
          [523, 6, 8, 0x3C],
          [779, 7, 9, 0x7D],
          [1291, 6, 11, 0x3D],
          [-32, 9, 32, 0x1FE, 'lower'],
          [3339, 9, 32, 0x1FF], // upper
          [2, 0x0] // OOB
        ];
        break;
      case 10:
        lines = [
          [-21, 7, 4, 0x7A],
          [-5, 8, 0, 0xFC],
          [-4, 7, 0, 0x7B],
          [-3, 5, 0, 0x18],
          [-2, 2, 2, 0x0],
          [2, 5, 0, 0x19],
          [3, 6, 0, 0x36],
          [4, 7, 0, 0x7C],
          [5, 8, 0, 0xFD],
          [6, 2, 6, 0x1],
          [70, 5, 5, 0x1A],
          [102, 6, 5, 0x37],
          [134, 6, 6, 0x38],
          [198, 6, 7, 0x39],
          [326, 6, 8, 0x3A],
          [582, 6, 9, 0x3B],
          [1094, 6, 10, 0x3C],
          [2118, 7, 11, 0x7D],
          [-22, 8, 32, 0xFE, 'lower'],
          [4166, 8, 32, 0xFF], // upper
          [2, 0x2] // OOB
        ];
        break;
      case 11:
        lines = [
          [1, 1, 0, 0x0],
          [2, 2, 1, 0x2],
          [4, 4, 0, 0xC],
          [5, 4, 1, 0xD],
          [7, 5, 1, 0x1C],
          [9, 5, 2, 0x1D],
          [13, 6, 2, 0x3C],
          [17, 7, 2, 0x7A],
          [21, 7, 3, 0x7B],
          [29, 7, 4, 0x7C],
          [45, 7, 5, 0x7D],
          [77, 7, 6, 0x7E],
          [141, 7, 32, 0x7F] // upper
        ];
        break;
      case 12:
        lines = [
          [1, 1, 0, 0x0],
          [2, 2, 0, 0x2],
          [3, 3, 1, 0x6],
          [5, 5, 0, 0x1C],
          [6, 5, 1, 0x1D],
          [8, 6, 1, 0x3C],
          [10, 7, 0, 0x7A],
          [11, 7, 1, 0x7B],
          [13, 7, 2, 0x7C],
          [17, 7, 3, 0x7D],
          [25, 7, 4, 0x7E],
          [41, 8, 5, 0xFE],
          [73, 8, 32, 0xFF] // upper
        ];
        break;
      case 13:
        lines = [
          [1, 1, 0, 0x0],
          [2, 3, 0, 0x4],
          [3, 4, 0, 0xC],
          [4, 5, 0, 0x1C],
          [5, 4, 1, 0xD],
          [7, 3, 3, 0x5],
          [15, 6, 1, 0x3A],
          [17, 6, 2, 0x3B],
          [21, 6, 3, 0x3C],
          [29, 6, 4, 0x3D],
          [45, 6, 5, 0x3E],
          [77, 7, 6, 0x7E],
          [141, 7, 32, 0x7F] // upper
        ];
        break;
      case 14:
        lines = [
          [-2, 3, 0, 0x4],
          [-1, 3, 0, 0x5],
          [0, 1, 0, 0x0],
          [1, 3, 0, 0x6],
          [2, 3, 0, 0x7]
        ];
        break;
      case 15:
        lines = [
          [-24, 7, 4, 0x7C],
          [-8, 6, 2, 0x3C],
          [-4, 5, 1, 0x1C],
          [-2, 4, 0, 0xC],
          [-1, 3, 0, 0x4],
          [0, 1, 0, 0x0],
          [1, 3, 0, 0x5],
          [2, 4, 0, 0xD],
          [3, 5, 1, 0x1D],
          [5, 6, 2, 0x3D],
          [9, 7, 4, 0x7D],
          [-25, 7, 32, 0x7E, 'lower'],
          [25, 7, 32, 0x7F] // upper
        ];
        break;
      default:
        throw new Jbig2Error(`standard table B.${number} does not exist`);
    }

    let length = lines.length, i;
    for (i = 0; i < length; i++) {
      lines[i] = new HuffmanLine(lines[i]);
    }
    table = new HuffmanTable(lines, true);
    standardTablesCache[number] = table;
    return table;
  }

  function Reader(data, start, end) {
    this.data = data;
    this.start = start;
    this.end = end;
    this.position = start;
    this.shift = -1;
    this.currentByte = 0;
  }

  Reader.prototype = {
    readBit() {
      if (this.shift < 0) {
        if (this.position >= this.end) {
          throw new Jbig2Error('end of data while reading bit');
        }
        this.currentByte = this.data[this.position++];
        this.shift = 7;
      }
      let bit = (this.currentByte >> this.shift) & 1;
      this.shift--;
      return bit;
    },

    readBits(numBits) {
      let result = 0, i;
      for (i = numBits - 1; i >= 0; i--) {
        result |= this.readBit() << i;
      }
      return result;
    },

    byteAlign() {
      this.shift = -1;
    },

    next() {
      if (this.position >= this.end) {
        return -1;
      }
      return this.data[this.position++];
    },
  };

  function getCustomHuffmanTable(index, referredTo, customTables) {
    // Returns a Tables segment that has been earlier decoded.
    // See 7.4.2.1.6 (symbol dictionary) or 7.4.3.1.6 (text region).
    let currentIndex = 0, i, ii = referredTo.length, table;
    for (i = 0; i < ii; i++) {
      table = customTables[referredTo[i]];
      if (table) {
        if (index === currentIndex) {
          return table;
        }
        currentIndex++;
      }
    }
    throw new Jbig2Error('can\'t find custom Huffman table');
  }

  function getTextRegionHuffmanTables(textRegion, referredTo, customTables,
                                      numberOfSymbols, reader) {
    // 7.4.3.1.7 Symbol ID Huffman table decoding

    // Read code lengths for RUNCODEs 0...34.
    let codes = [], i, codeLength;
    for (i = 0; i <= 34; i++) {
      codeLength = reader.readBits(4);
      codes.push(new HuffmanLine([i, codeLength, 0, 0]));
    }
    // Assign Huffman codes for RUNCODEs.
    let runCodesTable = new HuffmanTable(codes, false);

    // Read a Huffman code using the assignment above.
    // Interpret the RUNCODE codes and the additional bits (if any).
    codes.length = 0;
    for (i = 0; i < numberOfSymbols;) {
      codeLength = runCodesTable.decode(reader);
      if (codeLength >= 32) {
        let repeatedLength, numberOfRepeats, j;
        switch (codeLength) {
          case 32:
            if (i === 0) {
              throw new Jbig2Error('no previous value in symbol ID table');
            }
            numberOfRepeats = reader.readBits(2) + 3;
            repeatedLength = codes[i - 1].prefixLength;
            break;
          case 33:
            numberOfRepeats = reader.readBits(3) + 3;
            repeatedLength = 0;
            break;
          case 34:
            numberOfRepeats = reader.readBits(7) + 11;
            repeatedLength = 0;
            break;
          default:
            throw new Jbig2Error('invalid code length in symbol ID table');
        }
        for (j = 0; j < numberOfRepeats; j++) {
          codes.push(new HuffmanLine([i, repeatedLength, 0, 0]));
          i++;
        }
      } else {
        codes.push(new HuffmanLine([i, codeLength, 0, 0]));
        i++;
      }
    }
    reader.byteAlign();
    let symbolIDTable = new HuffmanTable(codes, false);

    // 7.4.3.1.6 Text region segment Huffman table selection

    let customIndex = 0, tableFirstS, tableDeltaS, tableDeltaT;

    switch (textRegion.huffmanFS) {
      case 0:
      case 1:
        tableFirstS = getStandardTable(textRegion.huffmanFS + 6);
        break;
      case 3:
        tableFirstS = getCustomHuffmanTable(customIndex, referredTo,
          customTables);
        customIndex++;
        break;
      default:
        throw new Jbig2Error('invalid Huffman FS selector');
    }

    switch (textRegion.huffmanDS) {
      case 0:
      case 1:
      case 2:
        tableDeltaS = getStandardTable(textRegion.huffmanDS + 8);
        break;
      case 3:
        tableDeltaS = getCustomHuffmanTable(customIndex, referredTo,
          customTables);
        customIndex++;
        break;
      default:
        throw new Jbig2Error('invalid Huffman DS selector');
    }

    switch (textRegion.huffmanDT) {
      case 0:
      case 1:
      case 2:
        tableDeltaT = getStandardTable(textRegion.huffmanDT + 11);
        break;
      case 3:
        tableDeltaT = getCustomHuffmanTable(customIndex, referredTo,
          customTables);
        customIndex++;
        break;
      default:
        throw new Jbig2Error('invalid Huffman DT selector');
    }

    if (textRegion.refinement) {
      // Load tables RDW, RDH, RDX and RDY.
      throw new Jbig2Error('refinement with Huffman is not supported');
    }

    return {
      symbolIDTable,
      tableFirstS,
      tableDeltaS,
      tableDeltaT,
    };
  }

  function getSymbolDictionaryHuffmanTables(dictionary, referredTo,
                                            customTables) {
    // 7.4.2.1.6 Symbol dictionary segment Huffman table selection

    let customIndex = 0, tableDeltaHeight, tableDeltaWidth;
    switch (dictionary.huffmanDHSelector) {
      case 0:
      case 1:
        tableDeltaHeight = getStandardTable(dictionary.huffmanDHSelector + 4);
        break;
      case 3:
        tableDeltaHeight = getCustomHuffmanTable(customIndex, referredTo,
          customTables);
        customIndex++;
        break;
      default:
        throw new Jbig2Error('invalid Huffman DH selector');
    }

    switch (dictionary.huffmanDWSelector) {
      case 0:
      case 1:
        tableDeltaWidth = getStandardTable(dictionary.huffmanDWSelector + 2);
        break;
      case 3:
        tableDeltaWidth = getCustomHuffmanTable(customIndex, referredTo,
          customTables);
        customIndex++;
        break;
      default:
        throw new Jbig2Error('invalid Huffman DW selector');
    }

    let tableBitmapSize, tableAggregateInstances;
    if (dictionary.bitmapSizeSelector) {
      tableBitmapSize = getCustomHuffmanTable(customIndex, referredTo,
        customTables);
      customIndex++;
    } else {
      tableBitmapSize = getStandardTable(1);
    }

    if (dictionary.aggregationInstancesSelector) {
      tableAggregateInstances = getCustomHuffmanTable(customIndex, referredTo,
        customTables);
    } else {
      tableAggregateInstances = getStandardTable(1);
    }

    return {
      tableDeltaHeight,
      tableDeltaWidth,
      tableBitmapSize,
      tableAggregateInstances,
    };
  }

  function readUncompressedBitmap(reader, width, height) {
    let bitmap = [], x, y, row;
    for (y = 0; y < height; y++) {
      row = new Uint8Array(width);
      bitmap.push(row);
      for (x = 0; x < width; x++) {
        row[x] = reader.readBit();
      }
      reader.byteAlign();
    }
    return bitmap;
  }

  function decodeMMRBitmap(input, width, height, endOfBlock) {
    // MMR is the same compression algorithm as the PDF filter
    // CCITTFaxDecode with /K -1.
    let params = {
      K: -1,
      Columns: width,
      Rows: height,
      BlackIs1: true,
      EndOfBlock: endOfBlock,
    };
    let decoder = new CCITTFaxDecoder(input, params);
    let bitmap = [], x, y, row, currentByte, shift, eof = false;

    for (y = 0; y < height; y++) {
      row = new Uint8Array(width);
      bitmap.push(row);
      shift = -1;
      for (x = 0; x < width; x++) {
        if (shift < 0) {
          currentByte = decoder.readNextChar();
          if (currentByte === -1) {
            // Set the rest of the bits to zero.
            currentByte = 0;
            eof = true;
          }
          shift = 7;
        }
        row[x] = (currentByte >> shift) & 1;
        shift--;
      }
    }

    if (endOfBlock && !eof) {
      // Read until EOFB has been consumed.
      const lookForEOFLimit = 5;
      for (let i = 0; i < lookForEOFLimit; i++) {
        if (decoder.readNextChar() === -1) {
          break;
        }
      }
    }

    return bitmap;
  }

  function Jbig2Image() {}

  Jbig2Image.prototype = {
    parseChunks(chunks) {
      return parseJbig2Chunks(chunks);
    },

    parse(data) {
      const { imgData, width, height, } = parseJbig2(data);
      this.width = width;
      this.height = height;
      return imgData;
    },
  };

  return Jbig2Image;
})();

export {
  Jbig2Image,
};