Removing huffman tables; decoding context refactoring
This commit is contained in:
Yury Delendik
parent
2e5414cd18
commit
699abbd4f2
186
src/jbig2.js
186
src/jbig2.js
@ -168,14 +168,50 @@ var Jbig2Image = (function Jbig2ImageClosure() {
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return ArithmeticDecoder;
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})();
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// Utility data structures
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function ContextCache() {}
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ContextCache.prototype = {
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getContexts: function(id) {
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if (id in this)
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return this[id];
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return (this[id] = []);
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}
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};
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function DecodingContext(data, start, end) {
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this.data = data;
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this.start = start;
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this.end = end;
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}
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DecodingContext.prototype = {
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get decoder() {
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var decoder = new ArithmeticDecoder(this.data, this.start, this.end);
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Object.defineProperty(this, 'decoder', {
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value: decoder,
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writable: false,
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configurable: true,
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enumerable: true
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});
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return decoder;
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},
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get contextCache() {
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var cache = new ContextCache();
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Object.defineProperty(this, 'contextCache', {
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value: cache,
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writable: false,
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configurable: true,
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enumerable: true
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});
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return cache;
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}
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};
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// Annex A. Arithmetic Integer Decoding Procedure
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// A.2 Procedure for decoding values
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function decodeInteger(contextCache, procedure, decoder) {
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var contexts;
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if (procedure in contextCache)
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contexts = contextCache[procedure];
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else
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contextCache[procedure] = contexts = [];
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var contexts = contextCache.getContexts(procedure);
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var prev = 1;
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var state = 1, v = 0, s;
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@ -232,13 +268,10 @@ var Jbig2Image = (function Jbig2ImageClosure() {
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v += offset;
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return !s ? v : v > 0 ? -v : null;
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}
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// A.3 The IAID decoding procedure
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function decodeIAID(contextCache, decoder, codeLength) {
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var contexts;
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if ('IAID' in contextCache)
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contexts = contextCache['IAID'];
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else
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contextCache['IAID'] = contexts = [];
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var contexts = contextCache.getContexts('IAID');
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var prev = 1;
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for (var i = 0; i < codeLength; i++) {
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@ -254,41 +287,6 @@ var Jbig2Image = (function Jbig2ImageClosure() {
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return prev - Math.pow(2, codeLength);
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}
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// Annex B. Huffman Table Decoding Procedure
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// B.5 Standard Huffman tables
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function TableB1(reader) {
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if (!reader.readBit())
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return reader.readBits(4); // 0 + VAL
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if (!reader.readBit())
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return reader.readBits(8) + 16; // 10 + (VAL - 16)
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if (!reader.readBit())
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return reader.readBits(16) + 272; // 110 + (VAL - 272)
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if (!reader.readBit())
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return reader.readBits(32) + 65808; // 1110 + (VAL - 65808)
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}
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function TableB2(reader) {
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if (!reader.readBit())
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return 0; // 0
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if (!reader.readBit())
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return 1; // 10
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if (!reader.readBit())
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return 2; // 110
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if (!reader.readBit())
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return reader.readBits(3) + 3; // 1110 + (VAL - 3)
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if (!reader.readBit())
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return reader.readBits(6) + 11; // 11110 + (VAL - 11)
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if (!reader.readBit())
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return reader.readBits(32) + 75; // 111110 + (VAL - 75)
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return null; // OOB
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}
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function TableB3(reader) {}
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function TableB4(reader) {}
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function TableB5(reader) {}
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// 7.3 Segment types
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var SegmentTypes = [
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'SymbolDictionary', null, null, null, 'IntermediateTextRegion', null,
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@ -374,7 +372,7 @@ var Jbig2Image = (function Jbig2ImageClosure() {
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// 6.2 Generic Region Decoding Procedure
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function decodeBitmap(mmr, width, height, templateIndex, prediction, skip, at,
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data, start, end) {
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decodingContext) {
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if (mmr)
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throw 'MMR encoding is not supported';
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@ -390,23 +388,14 @@ var Jbig2Image = (function Jbig2ImageClosure() {
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var pseudoPixelContext = ReusedContexts[templateIndex];
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var bitmap = [];
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var decoder, contexts, cx;
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if (data instanceof ArithmeticDecoder) {
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decoder = data;
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var contextCache = start;
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if ('GB' in contextCache)
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contexts = contextCache['GB'];
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else
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contextCache['GB'] = contexts = [];
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} else {
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decoder = new ArithmeticDecoder(data, start, end);
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contexts = [];
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}
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var decoder = decodingContext.decoder;
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var contexts = decodingContext.contextCache.getContexts('GB');
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var ltp = 0;
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for (var i = 0; i < height; i++) {
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if (prediction) {
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cx = contexts[pseudoPixelContext];
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var cx = contexts[pseudoPixelContext];
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if (!cx)
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contexts[pseudoPixelContext] = cx = {index: 0, mps: 0};
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var sltp = decoder.readBit(cx);
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@ -431,7 +420,7 @@ var Jbig2Image = (function Jbig2ImageClosure() {
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else
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contextLabel = (contextLabel << 1) | bitmap[i0][j0];
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}
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cx = contexts[contextLabel];
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var cx = contexts[contextLabel];
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if (!cx)
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contexts[contextLabel] = cx = {index: 0, mps: 0};
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var pixel = decoder.readBit(cx);
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@ -444,7 +433,7 @@ var Jbig2Image = (function Jbig2ImageClosure() {
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// 6.3.2 Generic Refinement Region Decoding Procedure
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function decodeRefinement(width, height, templateIndex, referenceBitmap,
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offsetX, offsetY, prediction, at,
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data, start, end) {
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decodingContext) {
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var codingTemplate = RefinementTemplates[templateIndex].coding;
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if (templateIndex == 0)
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codingTemplate = codingTemplate.concat([at[0]]);
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@ -470,23 +459,14 @@ var Jbig2Image = (function Jbig2ImageClosure() {
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var pseudoPixelContext = RefinementReusedContexts[templateIndex];
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var bitmap = [];
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var decoder, contexts, cx;
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if (data instanceof ArithmeticDecoder) {
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decoder = data;
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var contextCache = start;
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if ('GR' in contextCache)
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contexts = contextCache['GR'];
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else
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contextCache['GR'] = contexts = [];
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} else {
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decoder = new ArithmeticDecoder(data, start, end);
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contexts = [];
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}
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var decoder = decodingContext.decoder;
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var contexts = decodingContext.contextCache.getContexts('GR');
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var ltp = 0;
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for (var i = 0; i < height; i++) {
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if (prediction) {
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cx = contexts[pseudoPixelContext];
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var cx = contexts[pseudoPixelContext];
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if (!cx)
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contexts[pseudoPixelContext] = cx = {index: 0, mps: 0};
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var sltp = decoder.readBit(cx);
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@ -514,7 +494,7 @@ var Jbig2Image = (function Jbig2ImageClosure() {
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else
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contextLabel = (contextLabel << 1) | referenceBitmap[i0][j0];
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}
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cx = contexts[contextLabel];
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var cx = contexts[contextLabel];
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if (!cx)
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contexts[contextLabel] = cx = {index: 0, mps: 0};
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var pixel = decoder.readBit(cx);
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@ -530,15 +510,17 @@ var Jbig2Image = (function Jbig2ImageClosure() {
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numberOfNewSymbols, numberOfExportedSymbols,
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huffmanTables, templateIndex, at,
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refinementTemplateIndex, refinementAt,
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data, start, end) {
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decodingContext) {
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if (huffman)
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throw 'huffman is not supported';
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var newSymbols = [];
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var currentHeight = 0;
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var contextCache = {};
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var symbolCodeLength = log2(symbols.length + numberOfNewSymbols);
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var decoder = new ArithmeticDecoder(data, start, end);
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var decoder = decodingContext.decoder;
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var contextCache = decodingContext.contextCache;
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while (newSymbols.length < numberOfNewSymbols) {
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var deltaHeight = decodeInteger(contextCache, 'IADH', decoder); // 6.5.6
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currentHeight += deltaHeight;
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@ -563,11 +545,11 @@ var Jbig2Image = (function Jbig2ImageClosure() {
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newSymbols[symbolId - symbols.length];
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bitmap = decodeRefinement(currentWidth, currentHeight,
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refinementTemplateIndex, symbol, rdx, rdy, false, refinementAt,
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decoder, contextCache);
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decodingContext);
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} else {
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// 6.5.8.1 Direct-coded symbol bitmap
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bitmap = decodeBitmap(false, currentWidth, currentHeight,
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templateIndex, false, null, at, decoder, contextCache);
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templateIndex, false, null, at, decodingContext);
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}
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newSymbols.push(bitmap);
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}
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@ -594,7 +576,7 @@ var Jbig2Image = (function Jbig2ImageClosure() {
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transposed, dsOffset, referenceCorner,
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combinationOperator, huffmanTables,
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refinementTemplateIndex, refinementAt,
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data, start, end) {
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decodingContext) {
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if (huffman)
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throw 'huffman is not supported';
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@ -609,8 +591,8 @@ var Jbig2Image = (function Jbig2ImageClosure() {
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bitmap.push(row);
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}
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var contextCache = {};
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var decoder = new ArithmeticDecoder(data, start, end);
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var decoder = decodingContext.decoder;
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var contextCache = decodingContext.contextCache;
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if (transposed)
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throw 'transposed!=0 is not supported';
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@ -647,7 +629,7 @@ var Jbig2Image = (function Jbig2ImageClosure() {
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symbolBitmap = decodeRefinement(symbolWidth, symbolHeight,
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refinementTemplateIndex, symbolBitmap, (rdw >> 1) + rdx,
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(rdh >> 1) + rdy, false, refinementAt,
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decoder, contextCache);
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decodingContext);
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}
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var offsetT = t - ((referenceCorner & 1) ? 0 : symbolHeight);
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var offsetS = currentS - ((referenceCorner & 2) ? symbolWidth : 0);
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@ -1007,64 +989,58 @@ var Jbig2Image = (function Jbig2ImageClosure() {
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function SimpleSegmentVisitor_ImmediateGenericRegion(region, data,
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start, end) {
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var regionInfo = region.info;
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var decodingContext = new DecodingContext(data, start, end);
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var bitmap = decodeBitmap(region.mmr, regionInfo.width, regionInfo.height,
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region.template, region.prediction, null,
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region.at, data, start, end);
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region.at, decodingContext);
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this.drawBitmap(regionInfo, bitmap);
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},
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SymbolDictionary:
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function SimpleSegmentVisitor_SymbolDictionary(dictionary, currentSegment,
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referredSegments,
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data, start, end) {
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var symbols = this.symbols;
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var huffmanTables;
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if (dictionary.huffman) {
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huffmanTables = {};
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huffmanTables.DeltaHeights = dictionary.huffmanDHSelector == 0 ?
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TableB4 : dictionary.huffmanDHSelector == 1 ? TableB5 :
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this.userTable;
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huffmanTables.DeltaWidths = dictionary.huffmanDHSelector == 0 ?
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TableB2 : dictionary.huffmanDHSelector == 2 ? TableB3 :
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this.userTable;
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huffmanTables.BitmapSize = dictionary.huffmanBitmapSizeSelector == 0 ?
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TableB1 : this.userTable;
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huffmanTables.AggregationInstances =
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dictionary.aggregationInstancesSelector == 0 ? TableB1 :
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this.userTable;
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}
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if (dictionary.huffman)
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throw 'huffman is not supported';
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// Combines exported symbols from all referred segments
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var symbols = this.symbols;
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if (!symbols)
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this.symbols = symbols = {};
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var inputSymbols = [];
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for (var i = 0; i < referredSegments.length; i++)
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inputSymbols = inputSymbols.concat(symbols[referredSegments[i]]);
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if (!symbols)
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this.symbols = symbols = {};
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var decodingContext = new DecodingContext(data, start, end);
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symbols[currentSegment] = decodeSymbolDictionary(dictionary.huffman,
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dictionary.refinement, inputSymbols, dictionary.numberOfNewSymbols,
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dictionary.numberOfExportedSymbols, huffmanTables,
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dictionary.template, dictionary.at,
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dictionary.refinementTemplate, dictionary.refinementAt,
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data, start, end);
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decodingContext);
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},
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ImmediateTextRegion:
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function SimpleSegmentVisitor_ImmediateTextRegion(region,
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referredSegments,
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data, start, end) {
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var regionInfo = region.info;
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var symbols = this.symbols;
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var huffmanTables;
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// Combines exported symbols from all referred segments
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var symbols = this.symbols;
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var inputSymbols = [];
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for (var i = 0; i < referredSegments.length; i++)
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inputSymbols = inputSymbols.concat(symbols[referredSegments[i]]);
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var symbolCodeLength = log2(inputSymbols.length);
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var decodingContext = new DecodingContext(data, start, end);
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var bitmap = decodeTextRegion(region.huffman, region.refinement,
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regionInfo.width, regionInfo.height, region.defaultPixelValue,
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region.numberOfSymbolInstances, region.stripSize, inputSymbols,
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symbolCodeLength, region.transposed, region.dsOffset,
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region.referenceCorner, region.combinationOperator, huffmanTables,
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region.refinementTemplate, region.refinementAt, data, start, end);
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region.refinementTemplate, region.refinementAt, decodingContext);
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this.drawBitmap(regionInfo, bitmap);
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}
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};
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