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);
+ Object.defineProperty(this, 'decoder', {
+ value: decoder,
+ writable: false,
+ configurable: true,
+ enumerable: true
+ });
+ return decoder;
+ },
+ get contextCache() {
+ var cache = new ContextCache();
+ Object.defineProperty(this, 'contextCache', {
+ value: cache,
+ writable: false,
+ configurable: true,
+ enumerable: true
+ });
+ return cache;
+ }
+ };
+
// Annex A. Arithmetic Integer Decoding Procedure
// A.2 Procedure for decoding values
function decodeInteger(contextCache, procedure, decoder) {
- var contexts;
- if (procedure in contextCache)
- contexts = contextCache[procedure];
- else
- contextCache[procedure] = contexts = [];
+ var contexts = contextCache.getContexts(procedure);
var prev = 1;
var state = 1, v = 0, s;
v += offset;
return !s ? v : v > 0 ? -v : null;
}
+
// A.3 The IAID decoding procedure
function decodeIAID(contextCache, decoder, codeLength) {
- var contexts;
- if ('IAID' in contextCache)
- contexts = contextCache['IAID'];
- else
- contextCache['IAID'] = contexts = [];
+ var contexts = contextCache.getContexts('IAID');
var prev = 1;
for (var i = 0; i < codeLength; i++) {
return prev - Math.pow(2, codeLength);
}
- // Annex B. Huffman Table Decoding Procedure
- // B.5 Standard Huffman tables
- function TableB1(reader) {
- if (!reader.readBit())
- return reader.readBits(4); // 0 + VAL
- if (!reader.readBit())
- return reader.readBits(8) + 16; // 10 + (VAL - 16)
- if (!reader.readBit())
- return reader.readBits(16) + 272; // 110 + (VAL - 272)
- if (!reader.readBit())
- return reader.readBits(32) + 65808; // 1110 + (VAL - 65808)
- }
-
- function TableB2(reader) {
- if (!reader.readBit())
- return 0; // 0
- if (!reader.readBit())
- return 1; // 10
- if (!reader.readBit())
- return 2; // 110
- if (!reader.readBit())
- return reader.readBits(3) + 3; // 1110 + (VAL - 3)
- if (!reader.readBit())
- return reader.readBits(6) + 11; // 11110 + (VAL - 11)
- if (!reader.readBit())
- return reader.readBits(32) + 75; // 111110 + (VAL - 75)
- return null; // OOB
- }
-
- function TableB3(reader) {}
-
- function TableB4(reader) {}
-
- function TableB5(reader) {}
-
// 7.3 Segment types
var SegmentTypes = [
'SymbolDictionary', null, null, null, 'IntermediateTextRegion', null,
// 6.2 Generic Region Decoding Procedure
function decodeBitmap(mmr, width, height, templateIndex, prediction, skip, at,
- data, start, end) {
+ decodingContext) {
if (mmr)
throw 'MMR encoding is not supported';
var pseudoPixelContext = ReusedContexts[templateIndex];
var bitmap = [];
- var decoder, contexts, cx;
- if (data instanceof ArithmeticDecoder) {
- decoder = data;
- var contextCache = start;
- if ('GB' in contextCache)
- contexts = contextCache['GB'];
- else
- contextCache['GB'] = contexts = [];
- } else {
- decoder = new ArithmeticDecoder(data, start, end);
- contexts = [];
- }
+
+ var decoder = decodingContext.decoder;
+ var contexts = decodingContext.contextCache.getContexts('GB');
var ltp = 0;
for (var i = 0; i < height; i++) {
if (prediction) {
- cx = contexts[pseudoPixelContext];
+ var cx = contexts[pseudoPixelContext];
if (!cx)
contexts[pseudoPixelContext] = cx = {index: 0, mps: 0};
var sltp = decoder.readBit(cx);
else
contextLabel = (contextLabel << 1) | bitmap[i0][j0];
}
- cx = contexts[contextLabel];
+ var cx = contexts[contextLabel];
if (!cx)
contexts[contextLabel] = cx = {index: 0, mps: 0};
var pixel = decoder.readBit(cx);
// 6.3.2 Generic Refinement Region Decoding Procedure
function decodeRefinement(width, height, templateIndex, referenceBitmap,
offsetX, offsetY, prediction, at,
- data, start, end) {
+ decodingContext) {
var codingTemplate = RefinementTemplates[templateIndex].coding;
if (templateIndex == 0)
codingTemplate = codingTemplate.concat([at[0]]);
var pseudoPixelContext = RefinementReusedContexts[templateIndex];
var bitmap = [];
- var decoder, contexts, cx;
- if (data instanceof ArithmeticDecoder) {
- decoder = data;
- var contextCache = start;
- if ('GR' in contextCache)
- contexts = contextCache['GR'];
- else
- contextCache['GR'] = contexts = [];
- } else {
- decoder = new ArithmeticDecoder(data, start, end);
- contexts = [];
- }
+
+ var decoder = decodingContext.decoder;
+ var contexts = decodingContext.contextCache.getContexts('GR');
var ltp = 0;
for (var i = 0; i < height; i++) {
if (prediction) {
- cx = contexts[pseudoPixelContext];
+ var cx = contexts[pseudoPixelContext];
if (!cx)
contexts[pseudoPixelContext] = cx = {index: 0, mps: 0};
var sltp = decoder.readBit(cx);
else
contextLabel = (contextLabel << 1) | referenceBitmap[i0][j0];
}
- cx = contexts[contextLabel];
+ var cx = contexts[contextLabel];
if (!cx)
contexts[contextLabel] = cx = {index: 0, mps: 0};
var pixel = decoder.readBit(cx);
numberOfNewSymbols, numberOfExportedSymbols,
huffmanTables, templateIndex, at,
refinementTemplateIndex, refinementAt,
- data, start, end) {
+ decodingContext) {
if (huffman)
throw 'huffman is not supported';
var newSymbols = [];
var currentHeight = 0;
- var contextCache = {};
var symbolCodeLength = log2(symbols.length + numberOfNewSymbols);
- var decoder = new ArithmeticDecoder(data, start, end);
+
+ var decoder = decodingContext.decoder;
+ var contextCache = decodingContext.contextCache;
+
while (newSymbols.length < numberOfNewSymbols) {
var deltaHeight = decodeInteger(contextCache, 'IADH', decoder); // 6.5.6
currentHeight += deltaHeight;
newSymbols[symbolId - symbols.length];
bitmap = decodeRefinement(currentWidth, currentHeight,
refinementTemplateIndex, symbol, rdx, rdy, false, refinementAt,
- decoder, contextCache);
+ decodingContext);
} else {
// 6.5.8.1 Direct-coded symbol bitmap
bitmap = decodeBitmap(false, currentWidth, currentHeight,
- templateIndex, false, null, at, decoder, contextCache);
+ templateIndex, false, null, at, decodingContext);
}
newSymbols.push(bitmap);
}
transposed, dsOffset, referenceCorner,
combinationOperator, huffmanTables,
refinementTemplateIndex, refinementAt,
- data, start, end) {
+ decodingContext) {
if (huffman)
throw 'huffman is not supported';
bitmap.push(row);
}
- var contextCache = {};
- var decoder = new ArithmeticDecoder(data, start, end);
+ var decoder = decodingContext.decoder;
+ var contextCache = decodingContext.contextCache;
if (transposed)
throw 'transposed!=0 is not supported';
symbolBitmap = decodeRefinement(symbolWidth, symbolHeight,
refinementTemplateIndex, symbolBitmap, (rdw >> 1) + rdx,
(rdh >> 1) + rdy, false, refinementAt,
- decoder, contextCache);
+ decodingContext);
}
var offsetT = t - ((referenceCorner & 1) ? 0 : symbolHeight);
var offsetS = currentS - ((referenceCorner & 2) ? symbolWidth : 0);
function SimpleSegmentVisitor_ImmediateGenericRegion(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, data, start, end);
+ region.at, decodingContext);
this.drawBitmap(regionInfo, bitmap);
},
SymbolDictionary:
function SimpleSegmentVisitor_SymbolDictionary(dictionary, currentSegment,
referredSegments,
data, start, end) {
- var symbols = this.symbols;
var huffmanTables;
- if (dictionary.huffman) {
- huffmanTables = {};
- huffmanTables.DeltaHeights = dictionary.huffmanDHSelector == 0 ?
- TableB4 : dictionary.huffmanDHSelector == 1 ? TableB5 :
- this.userTable;
- huffmanTables.DeltaWidths = dictionary.huffmanDHSelector == 0 ?
- TableB2 : dictionary.huffmanDHSelector == 2 ? TableB3 :
- this.userTable;
- huffmanTables.BitmapSize = dictionary.huffmanBitmapSizeSelector == 0 ?
- TableB1 : this.userTable;
- huffmanTables.AggregationInstances =
- dictionary.aggregationInstancesSelector == 0 ? TableB1 :
- this.userTable;
- }
+ if (dictionary.huffman)
+ throw 'huffman is not supported';
+
// Combines exported symbols from all referred segments
+ var symbols = this.symbols;
+ if (!symbols)
+ this.symbols = symbols = {};
+
var inputSymbols = [];
for (var i = 0; i < referredSegments.length; i++)
inputSymbols = inputSymbols.concat(symbols[referredSegments[i]]);
- if (!symbols)
- this.symbols = symbols = {};
+ 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,
- data, start, end);
+ decodingContext);
},
ImmediateTextRegion:
function SimpleSegmentVisitor_ImmediateTextRegion(region,
referredSegments,
data, start, end) {
var regionInfo = region.info;
- var symbols = this.symbols;
var huffmanTables;
+
// Combines exported symbols from all referred segments
+ var symbols = this.symbols;
var inputSymbols = [];
for (var i = 0; i < referredSegments.length; i++)
inputSymbols = inputSymbols.concat(symbols[referredSegments[i]]);
var symbolCodeLength = log2(inputSymbols.length);
+ 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, data, start, end);
+ region.refinementTemplate, region.refinementAt, decodingContext);
this.drawBitmap(regionInfo, bitmap);
}
};
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