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jbig2.js
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/* -*- Mode: Java; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set shiftwidth=2 tabstop=2 autoindent cindent expandtab: */
/* 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.
*/
'use strict';
var Jbig2Image = (function Jbig2ImageClosure() {
// Annex E. Arithmetic Coding
var ArithmeticDecoder = (function ArithmeticDecoderClosure() {
var QeTable = [
{qe: 0x5601, nmps: 1, nlps: 1, switchFlag: 1},
{qe: 0x3401, nmps: 2, nlps: 6, switchFlag: 0},
{qe: 0x1801, nmps: 3, nlps: 9, switchFlag: 0},
{qe: 0x0AC1, nmps: 4, nlps: 12, switchFlag: 0},
{qe: 0x0521, nmps: 5, nlps: 29, switchFlag: 0},
{qe: 0x0221, nmps: 38, nlps: 33, switchFlag: 0},
{qe: 0x5601, nmps: 7, nlps: 6, switchFlag: 1},
{qe: 0x5401, nmps: 8, nlps: 14, switchFlag: 0},
{qe: 0x4801, nmps: 9, nlps: 14, switchFlag: 0},
{qe: 0x3801, nmps: 10, nlps: 14, switchFlag: 0},
{qe: 0x3001, nmps: 11, nlps: 17, switchFlag: 0},
{qe: 0x2401, nmps: 12, nlps: 18, switchFlag: 0},
{qe: 0x1C01, nmps: 13, nlps: 20, switchFlag: 0},
{qe: 0x1601, nmps: 29, nlps: 21, switchFlag: 0},
{qe: 0x5601, nmps: 15, nlps: 14, switchFlag: 1},
{qe: 0x5401, nmps: 16, nlps: 14, switchFlag: 0},
{qe: 0x5101, nmps: 17, nlps: 15, switchFlag: 0},
{qe: 0x4801, nmps: 18, nlps: 16, switchFlag: 0},
{qe: 0x3801, nmps: 19, nlps: 17, switchFlag: 0},
{qe: 0x3401, nmps: 20, nlps: 18, switchFlag: 0},
{qe: 0x3001, nmps: 21, nlps: 19, switchFlag: 0},
{qe: 0x2801, nmps: 22, nlps: 19, switchFlag: 0},
{qe: 0x2401, nmps: 23, nlps: 20, switchFlag: 0},
{qe: 0x2201, nmps: 24, nlps: 21, switchFlag: 0},
{qe: 0x1C01, nmps: 25, nlps: 22, switchFlag: 0},
{qe: 0x1801, nmps: 26, nlps: 23, switchFlag: 0},
{qe: 0x1601, nmps: 27, nlps: 24, switchFlag: 0},
{qe: 0x1401, nmps: 28, nlps: 25, switchFlag: 0},
{qe: 0x1201, nmps: 29, nlps: 26, switchFlag: 0},
{qe: 0x1101, nmps: 30, nlps: 27, switchFlag: 0},
{qe: 0x0AC1, nmps: 31, nlps: 28, switchFlag: 0},
{qe: 0x09C1, nmps: 32, nlps: 29, switchFlag: 0},
{qe: 0x08A1, nmps: 33, nlps: 30, switchFlag: 0},
{qe: 0x0521, nmps: 34, nlps: 31, switchFlag: 0},
{qe: 0x0441, nmps: 35, nlps: 32, switchFlag: 0},
{qe: 0x02A1, nmps: 36, nlps: 33, switchFlag: 0},
{qe: 0x0221, nmps: 37, nlps: 34, switchFlag: 0},
{qe: 0x0141, nmps: 38, nlps: 35, switchFlag: 0},
{qe: 0x0111, nmps: 39, nlps: 36, switchFlag: 0},
{qe: 0x0085, nmps: 40, nlps: 37, switchFlag: 0},
{qe: 0x0049, nmps: 41, nlps: 38, switchFlag: 0},
{qe: 0x0025, nmps: 42, nlps: 39, switchFlag: 0},
{qe: 0x0015, nmps: 43, nlps: 40, switchFlag: 0},
{qe: 0x0009, nmps: 44, nlps: 41, switchFlag: 0},
{qe: 0x0005, nmps: 45, nlps: 42, switchFlag: 0},
{qe: 0x0001, nmps: 45, nlps: 43, switchFlag: 0},
{qe: 0x5601, nmps: 46, nlps: 46, switchFlag: 0}
];
function ArithmeticDecoder(data, start, end) {
this.data = data;
this.bp = start;
this.dataEnd = end;
this.chigh = data[start];
this.clow = 0;
this.byteIn();
this.chigh = ((this.chigh << 7) & 0xFFFF) | ((this.clow >> 9) & 0x7F);
this.clow = (this.clow << 7) & 0xFFFF;
this.ct -= 7;
this.a = 0x8000;
}
ArithmeticDecoder.prototype = {
byteIn: function ArithmeticDecoder_byteIn() {
var data = this.data;
var bp = this.bp;
if (data[bp] == 0xFF) {
var b1 = data[bp + 1];
if (b1 > 0x8F) {
this.clow += 0xFF00;
this.ct = 8;
} else {
bp++;
this.clow += (data[bp] << 9);
this.ct = 7;
this.bp = bp;
}
} else {
bp++;
this.clow += bp < this.dataEnd ? (data[bp] << 8) : 0xFF00;
this.ct = 8;
this.bp = bp;
}
if (this.clow > 0xFFFF) {
this.chigh += (this.clow >> 16);
this.clow &= 0xFFFF;
}
},
readBit: function ArithmeticDecoder_readBit(cx) {
var qeIcx = QeTable[cx.index].qe;
this.a -= qeIcx;
if (this.chigh < qeIcx) {
var d = this.exchangeLps(cx);
this.renormD();
return d;
} else {
this.chigh -= qeIcx;
if ((this.a & 0x8000) == 0) {
var d = this.exchangeMps(cx);
this.renormD();
return d;
} else {
return cx.mps;
}
}
},
renormD: function ArithmeticDecoder_renormD() {
do {
if (this.ct == 0)
this.byteIn();
this.a <<= 1;
this.chigh = ((this.chigh << 1) & 0xFFFF) | ((this.clow >> 15) & 1);
this.clow = (this.clow << 1) & 0xFFFF;
this.ct--;
} while ((this.a & 0x8000) == 0);
},
exchangeMps: function ArithmeticDecoder_exchangeMps(cx) {
var d;
var qeTableIcx = QeTable[cx.index];
if (this.a < qeTableIcx.qe) {
d = 1 - cx.mps;
if (qeTableIcx.switchFlag == 1) {
cx.mps = 1 - cx.mps;
}
cx.index = qeTableIcx.nlps;
} else {
d = cx.mps;
cx.index = qeTableIcx.nmps;
}
return d;
},
exchangeLps: function ArithmeticDecoder_exchangeLps(cx) {
var d;
var qeTableIcx = QeTable[cx.index];
if (this.a < qeTableIcx.qe) {
this.a = qeTableIcx.qe;
d = cx.mps;
cx.index = qeTableIcx.nmps;
} else {
this.a = qeTableIcx.qe;
d = 1 - cx.mps;
if (qeTableIcx.switchFlag == 1) {
cx.mps = 1 - cx.mps;
}
cx.index = qeTableIcx.nlps;
}
return d;
}
};
return ArithmeticDecoder;
})();
// Utility data structures
function ContextCache() {}
ContextCache.prototype = {
getContexts: function(id) {
if (id in this)
return this[id];
return (this[id] = []);
}
};
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;
var state = 1, v = 0, s;
var toRead = 32, offset = 4436; // defaults for state 7
while (state) {
var cx = contexts[prev];
if (!cx)
contexts[prev] = cx = {index: 0, mps: 0};
var bit = decoder.readBit(cx);
prev = prev < 256 ? (prev << 1) | bit :
(((prev << 1) | bit) & 511) | 256;
switch (state) {
case 1:
s = !!bit;
break;
case 2:
if (bit) break;
state = 7;
toRead = 2;
offset = 0;
break;
case 3:
if (bit) break;
state = 7;
toRead = 4;
offset = 4;
break;
case 4:
if (bit) break;
state = 7;
toRead = 6;
offset = 20;
break;
case 5:
if (bit) break;
state = 7;
toRead = 8;
offset = 84;
break;
case 6:
if (bit) break;
state = 7;
toRead = 12;
offset = 340;
break;
default:
v = v * 2 + bit;
if (--toRead == 0)
state = 0;
continue;
}
state++;
}
v += offset;
return !s ? v : v > 0 ? -v : 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 cx = contexts[prev];
if (!cx)
contexts[prev] = cx = {index: 0, mps: 0};
var bit = decoder.readBit(cx);
prev = (prev * 2) + bit;
}
if (codeLength < 31)
return prev & ((1 << codeLength) - 1);
else
return prev - Math.pow(2, codeLength);
}
// 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: -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}]
}
];
var ReusedContexts = [
0x1CD3, // '00111001101' (template) + '0011' (at),
0x079A, // '001111001101' + '0',
0x00E3, // '001110001' + '1',
0x018B // '011000101' + '1'
];
var RefinementReusedContexts = [
0x0020, // '000' + '0' (coding) + '00010000' + '0' (reference)
0x0008 // '0000' + '001000'
];
function log2(x) {
var n = 1, i = 0;
while (x > n) {
n <<= 1;
i++;
}
return i;
}
function readInt32(data, start) {
return (data[start] << 24) | (data[start + 1] << 16) |
(data[start + 2] << 8) | data[start + 3];
}
function readUint32(data, start) {
var value = readInt32(data, start);
return value & 0x80000000 ? (value + 4294967296) : value;
}
function readUint16(data, start) {
return (data[start] << 8) | data[start + 1];
}
function readInt8(data, start) {
return (data[start] << 24) >> 24;
}
// 6.2 Generic Region Decoding Procedure
function decodeBitmap(mmr, width, height, templateIndex, prediction, skip, at,
decodingContext) {
if (mmr)
error('JBIG2 error: MMR encoding is not supported');
var useskip = !!skip;
var template = CodingTemplates[templateIndex].concat(at);
var templateLength = template.length;
var templateX = new Int32Array(templateLength);
var templateY = new Int32Array(templateLength);
for (var k = 0; k < templateLength; k++) {
templateX[k] = template[k].x;
templateY[k] = template[k].y;
}
var pseudoPixelContext = ReusedContexts[templateIndex];
var bitmap = [];
var decoder = decodingContext.decoder;
var contexts = decodingContext.contextCache.getContexts('GB');
var ltp = 0;
for (var i = 0; i < height; i++) {
if (prediction) {
var cx = contexts[pseudoPixelContext];
if (!cx)
contexts[pseudoPixelContext] = cx = {index: 0, mps: 0};
var sltp = decoder.readBit(cx);
ltp ^= sltp;
}
if (ltp) {
bitmap.push(bitmap[bitmap.length - 1]); // duplicate previous row
continue;
}
var row = new Uint8Array(width);
bitmap.push(row);
for (var j = 0; j < width; j++) {
if (useskip && skip[i][j]) {
row[j] = 0;
continue;
}
var contextLabel = 0;
for (var k = 0; k < templateLength; k++) {
var i0 = i + templateY[k], j0 = j + templateX[k];
if (i0 < 0 || j0 < 0 || j0 >= width)
contextLabel <<= 1; // out of bound pixel
else
contextLabel = (contextLabel << 1) | bitmap[i0][j0];
}
var cx = contexts[contextLabel];
if (!cx)
contexts[contextLabel] = cx = {index: 0, mps: 0};
var pixel = decoder.readBit(cx);
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);
for (var 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 (var 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 cx = contexts[pseudoPixelContext];
if (!cx)
contexts[pseudoPixelContext] = cx = {index: 0, mps: 0};
var sltp = decoder.readBit(cx);
ltp ^= sltp;
}
var row = new Uint8Array(width);
bitmap.push(row);
for (var j = 0; j < width; j++) {
if (ltp)
error('JBIG2 error: prediction is not supported');
var contextLabel = 0;
for (var k = 0; k < codingTemplateLength; k++) {
var 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 (var k = 0; k < referenceTemplateLength; k++) {
var i0 = i + referenceTemplateY[k] + offsetY;
var 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 cx = contexts[contextLabel];
if (!cx)
contexts[contextLabel] = cx = {index: 0, mps: 0};
var pixel = decoder.readBit(cx);
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) {
if (huffman)
error('JBIG2 error: huffman is not supported');
var newSymbols = [];
var currentHeight = 0;
var symbolCodeLength = log2(symbols.length + numberOfNewSymbols);
var decoder = decodingContext.decoder;
var contextCache = decodingContext.contextCache;
while (newSymbols.length < numberOfNewSymbols) {
var deltaHeight = decodeInteger(contextCache, 'IADH', decoder); // 6.5.6
currentHeight += deltaHeight;
var currentWidth = 0;
var totalWidth = 0;
while (true) {
var deltaWidth = 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)
error('JBIG2 error: number of instances > 1 is not supported');
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);
} else {
// 6.5.8.1 Direct-coded symbol bitmap
bitmap = decodeBitmap(false, currentWidth, currentHeight,
templateIndex, false, null, at, decodingContext);
}
newSymbols.push(bitmap);
}
}
// 6.5.10 Exported symbols
var exportedSymbols = [];
var flags = [], currentFlag = false;
var totalSymbolsLength = symbols.length + numberOfNewSymbols;
while (flags.length < totalSymbolsLength) {
var runLength = 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) {
if (huffman)
error('JBIG2 error: huffman is not supported');
// Prepare bitmap
var bitmap = [];
for (var i = 0; i < height; i++) {
var 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;
if (transposed)
error('JBIG2 error: transposed is not supported');
var stripT = -decodeInteger(contextCache, 'IADT', decoder); // 6.4.6
var firstS = 0;
var i = 0;
while (i < numberOfSymbolInstances) {
var deltaT = decodeInteger(contextCache, 'IADT', decoder); // 6.4.6
stripT += deltaT;
var deltaFirstS = decodeInteger(contextCache, 'IAFS', decoder); // 6.4.7
firstS += deltaFirstS;
var currentS = firstS;
do {
var currentT = stripSize == 1 ? 0 :
decodeInteger(contextCache, 'IAIT', decoder); // 6.4.9
var t = stripSize * stripT + currentT;
var symbolId = decodeIAID(contextCache, decoder, symbolCodeLength);
var applyRefinement = refinement &&
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);
var offsetS = currentS - ((referenceCorner & 2) ? symbolWidth : 0);
for (var t2 = 0; t2 < symbolHeight; t2++) {
var row = bitmap[offsetT + t2];
if (!row) continue;
var symbolRow = symbolBitmap[t2];
switch (combinationOperator) {
case 0: // OR
for (var s2 = 0; s2 < symbolWidth; s2++)
row[offsetS + s2] |= symbolRow[s2];
break;
case 2: // XOR
for (var s2 = 0; s2 < symbolWidth; s2++)
row[offsetS + s2] ^= symbolRow[s2];
break;
default:
error('JBIG2 error: operator ' + combinationOperator +
' is not supported');
}
}
currentS += symbolWidth - 1;
i++;
var deltaS = decodeInteger(contextCache, 'IADS', decoder); // 6.4.8
if (deltaS == null)
break; // OOB
currentS += deltaS + dsOffset;
} while (true);
}
return bitmap;
}
function readSegmentHeader(data, start) {
var segmentHeader = {};
segmentHeader.number = readUint32(data, start);
var flags = data[start + 4];
var segmentType = flags & 0x3F;
if (!SegmentTypes[segmentType])
error('JBIG2 error: 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 = readInt32(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)
error('JBIG2 error: invalid referred-to flags');
segmentHeader.retainBits = retainBits;
var referredToSegmentNumberSize = segmentHeader.number <= 256 ? 1 :
segmentHeader.number <= 65536 ? 2 : 4;
var referredTo = [];
for (var 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);
if (segmentHeader.length == 0xFFFFFFFF)
error('JBIG2 error: unknown segment length is not supported');
position += 4;
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: 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;
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) {
var atLength = dictionary.template == 0 ? 4 : 1;
var at = [];
for (var 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) {
var at = [];
for (var 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.stripSize = 1 << ((textRegionSegmentFlags >> 2) & 3);
textRegion.referenceCorner = (textRegionSegmentFlags >> 4) & 3;
textRegion.transposed = !!(textRegionSegmentFlags & 64);
textRegion.combinationOperator = (textRegionSegmentFlags >> 7) & 3;
textRegion.defaultPixelValue = (textRegionSegmentFlags >> 9) & 1;
textRegion.dsOffset = (textRegionSegmentFlags >> 10) & 31;
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 & 14);
}
if (textRegion.refinement && !textRegion.refinementTemplate) {
var at = [];
for (var 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;
// TODO 7.4.3.1.7 Symbol ID Huffman table decoding
if (textRegion.huffman)
error('JBIG2 error: huffman is not supported');
args = [textRegion, 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) {
var atLength = genericRegion.template == 0 ? 4 : 1;
var at = [];
for (var 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];
var pageStripingInformatiom = readUint16(data, position + 17);
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 50: // EndOfStripe
break;
case 51: // EndOfFile
break;
default:
error('JBIG2 error: 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 parseJbig2(data, start, end) {
var position = start;
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)
error('JBIG2 error: invalid header');
var header = {};
position += 8;
var flags = data[position++];
header.randomAccess = !(flags & 1);
if (!(flags & 2)) {
header.numberOfPages = readUint32(data, position);
position += 4;
}
var segments = readSegments(header, data, position, end);
error('Not implemented');
// processSegments(segments, new SimpleSegmentVisitor());
}
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 SimpleSegmentVisitor() {}
SimpleSegmentVisitor.prototype = {
onPageInformation: function SimpleSegmentVisitor_onPageInformation(info) {
this.currentPageInfo = info;
var rowSize = (info.width + 7) >> 3;
var buffer = new Uint8Array(rowSize * info.height);
var fill = info.defaultPixelValue ? 0xFF : 0;
for (var i = 0, ii = buffer.length; i < ii; i++)
buffer[i] = fill;
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;
for (var i = 0; i < height; i++) {
var mask = 128 >> (regionInfo.x & 7);
var offset = (i + regionInfo.y) * rowSize + (regionInfo.x >> 3);
switch (combinationOperator) {
case 0: // OR
for (var j = 0; j < width; j++) {
buffer[offset] |= bitmap[i][j] ? mask : 0;
mask >>= 1;
if (!mask) {
mask = 128;
offset++;
}
}
break;
case 2: // XOR
for (var j = 0; j < width; j++) {
buffer[offset] ^= bitmap[i][j] ? mask : 0;
mask >>= 1;
if (!mask) {
mask = 128;
offset++;
}
}
break;
default:
error('JBIG2 error: operator ' + combinationOperator +
' is not supported');
}
}
},
onImmediateGenericRegion:
function SimpleSegmentVisitor_onImmediateGenericRegion(region, data,
start, end) {
var regionInfo = region.info;