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jpx.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.
*/
/* globals error, globalScope, warn */
'use strict';
var JpxImage = (function JpxImageClosure() {
// Table E.1
var SubbandsGainLog2 = {
'LL': 0,
'LH': 1,
'HL': 1,
'HH': 2
};
function JpxImage() {
this.failOnCorruptedImage = false;
}
JpxImage.prototype = {
load: function JpxImage_load(url) {
var xhr = new XMLHttpRequest();
xhr.open('GET', url, true);
xhr.responseType = 'arraybuffer';
xhr.onload = (function() {
// TODO catch parse error
var data = new Uint8Array(xhr.response || xhr.mozResponseArrayBuffer);
this.parse(data);
if (this.onload)
this.onload();
}).bind(this);
xhr.send(null);
},
parse: function JpxImage_parse(data) {
function readUint(data, offset, bytes) {
var n = 0;
for (var i = 0; i < bytes; i++)
n = n * 256 + (data[offset + i] & 0xFF);
return n;
}
var position = 0, length = data.length;
while (position < length) {
var headerSize = 8;
var lbox = readUint(data, position, 4);
var tbox = readUint(data, position + 4, 4);
position += headerSize;
if (lbox == 1) {
lbox = readUint(data, position, 8);
position += 8;
headerSize += 8;
}
if (lbox === 0)
lbox = length - position + headerSize;
if (lbox < headerSize)
error('JPX error: Invalid box field size');
var dataLength = lbox - headerSize;
var jumpDataLength = true;
switch (tbox) {
case 0x6A501A1A: // 'jP\032\032'
// TODO
break;
case 0x6A703268: // 'jp2h'
jumpDataLength = false; // parsing child boxes
break;
case 0x636F6C72: // 'colr'
// TODO
break;
case 0x6A703263: // 'jp2c'
this.parseCodestream(data, position, position + dataLength);
break;
}
if (jumpDataLength)
position += dataLength;
}
},
parseCodestream: function JpxImage_parseCodestream(data, start, end) {
var context = {};
try {
var position = start;
while (position < end) {
var code = readUint16(data, position);
position += 2;
var length = 0, j;
switch (code) {
case 0xFF4F: // Start of codestream (SOC)
context.mainHeader = true;
break;
case 0xFFD9: // End of codestream (EOC)
break;
case 0xFF51: // Image and tile size (SIZ)
length = readUint16(data, position);
var siz = {};
siz.Xsiz = readUint32(data, position + 4);
siz.Ysiz = readUint32(data, position + 8);
siz.XOsiz = readUint32(data, position + 12);
siz.YOsiz = readUint32(data, position + 16);
siz.XTsiz = readUint32(data, position + 20);
siz.YTsiz = readUint32(data, position + 24);
siz.XTOsiz = readUint32(data, position + 28);
siz.YTOsiz = readUint32(data, position + 32);
var componentsCount = readUint16(data, position + 36);
siz.Csiz = componentsCount;
var components = [];
j = position + 38;
for (var i = 0; i < componentsCount; i++) {
var component = {
precision: (data[j] & 0x7F) + 1,
isSigned: !!(data[j] & 0x80),
XRsiz: data[j + 1],
YRsiz: data[j + 1]
};
calculateComponentDimensions(component, siz);
components.push(component);
}
context.SIZ = siz;
context.components = components;
calculateTileGrids(context, components);
context.QCC = [];
context.COC = [];
break;
case 0xFF5C: // Quantization default (QCD)
length = readUint16(data, position);
var qcd = {};
j = position + 2;
var sqcd = data[j++];
var spqcdSize, scalarExpounded;
switch (sqcd & 0x1F) {
case 0:
spqcdSize = 8;
scalarExpounded = true;
break;
case 1:
spqcdSize = 16;
scalarExpounded = false;
break;
case 2:
spqcdSize = 16;
scalarExpounded = true;
break;
default:
throw 'Invalid SQcd value ' + sqcd;
}
qcd.noQuantization = spqcdSize == 8;
qcd.scalarExpounded = scalarExpounded;
qcd.guardBits = sqcd >> 5;
var spqcds = [];
while (j < length + position) {
var spqcd = {};
if (spqcdSize == 8) {
spqcd.epsilon = data[j++] >> 3;
spqcd.mu = 0;
} else {
spqcd.epsilon = data[j] >> 3;
spqcd.mu = ((data[j] & 0x7) << 8) | data[j + 1];
j += 2;
}
spqcds.push(spqcd);
}
qcd.SPqcds = spqcds;
if (context.mainHeader)
context.QCD = qcd;
else {
context.currentTile.QCD = qcd;
context.currentTile.QCC = [];
}
break;
case 0xFF5D: // Quantization component (QCC)
length = readUint16(data, position);
var qcc = {};
j = position + 2;
var cqcc;
if (context.SIZ.Csiz < 257)
cqcc = data[j++];
else {
cqcc = readUint16(data, j);
j += 2;
}
var sqcd = data[j++];
var spqcdSize, scalarExpounded;
switch (sqcd & 0x1F) {
case 0:
spqcdSize = 8;
scalarExpounded = true;
break;
case 1:
spqcdSize = 16;
scalarExpounded = false;
break;
case 2:
spqcdSize = 16;
scalarExpounded = true;
break;
default:
throw 'Invalid SQcd value ' + sqcd;
}
qcc.noQuantization = spqcdSize == 8;
qcc.scalarExpounded = scalarExpounded;
qcc.guardBits = sqcd >> 5;
var spqcds = [];
while (j < length + position) {
var spqcd = {};
if (spqcdSize == 8) {
spqcd.epsilon = data[j++] >> 3;
spqcd.mu = 0;
} else {
spqcd.epsilon = data[j] >> 3;
spqcd.mu = ((data[j] & 0x7) << 8) | data[j + 1];
j += 2;
}
spqcds.push(spqcd);
}
qcc.SPqcds = spqcds;
if (context.mainHeader)
context.QCC[cqcc] = qcc;
else
context.currentTile.QCC[cqcc] = qcc;
break;
case 0xFF52: // Coding style default (COD)
length = readUint16(data, position);
var cod = {};
j = position + 2;
var scod = data[j++];
cod.entropyCoderWithCustomPrecincts = !!(scod & 1);
cod.sopMarkerUsed = !!(scod & 2);
cod.ephMarkerUsed = !!(scod & 4);
var codingStyle = {};
cod.progressionOrder = data[j++];
cod.layersCount = readUint16(data, j);
j += 2;
cod.multipleComponentTransform = data[j++];
cod.decompositionLevelsCount = data[j++];
cod.xcb = (data[j++] & 0xF) + 2;
cod.ycb = (data[j++] & 0xF) + 2;
var blockStyle = data[j++];
cod.selectiveArithmeticCodingBypass = !!(blockStyle & 1);
cod.resetContextProbabilities = !!(blockStyle & 2);
cod.terminationOnEachCodingPass = !!(blockStyle & 4);
cod.verticalyStripe = !!(blockStyle & 8);
cod.predictableTermination = !!(blockStyle & 16);
cod.segmentationSymbolUsed = !!(blockStyle & 32);
cod.transformation = data[j++];
if (cod.entropyCoderWithCustomPrecincts) {
var precinctsSizes = {};
while (j < length + position) {
var precinctsSize = data[j];
precinctsSizes.push({
PPx: precinctsSize & 0xF,
PPy: precinctsSize >> 4
});
}
cod.precinctsSizes = precinctsSizes;
}
if (cod.sopMarkerUsed || cod.ephMarkerUsed ||
cod.selectiveArithmeticCodingBypass ||
cod.resetContextProbabilities ||
cod.terminationOnEachCodingPass ||
cod.verticalyStripe || cod.predictableTermination)
throw 'Unsupported COD options: ' +
globalScope.JSON.stringify(cod);
if (context.mainHeader)
context.COD = cod;
else {
context.currentTile.COD = cod;
context.currentTile.COC = [];
}
break;
case 0xFF90: // Start of tile-part (SOT)
length = readUint16(data, position);
var tile = {};
tile.index = readUint16(data, position + 2);
tile.length = readUint32(data, position + 4);
tile.dataEnd = tile.length + position - 2;
tile.partIndex = data[position + 8];
tile.partsCount = data[position + 9];
context.mainHeader = false;
if (tile.partIndex === 0) {
// reset component specific settings
tile.COD = context.COD;
tile.COC = context.COC.slice(0); // clone of the global COC
tile.QCD = context.QCD;
tile.QCC = context.QCC.slice(0); // clone of the global COC
}
context.currentTile = tile;
break;
case 0xFF93: // Start of data (SOD)
var tile = context.currentTile;
if (tile.partIndex === 0) {
initializeTile(context, tile.index);
buildPackets(context);
}
// moving to the end of the data
length = tile.dataEnd - position;
parseTilePackets(context, data, position, length);
break;
case 0xFF64: // Comment (COM)
length = readUint16(data, position);
// skipping content
break;
default:
throw 'Unknown codestream code: ' + code.toString(16);
}
position += length;
}
} catch (e) {
if (this.failOnCorruptedImage)
error('JPX error: ' + e);
else
warn('JPX error: ' + e + '. Trying to recover');
}
this.tiles = transformComponents(context);
this.width = context.SIZ.Xsiz - context.SIZ.XOsiz;
this.height = context.SIZ.Ysiz - context.SIZ.YOsiz;
this.componentsCount = context.SIZ.Csiz;
}
};
function readUint32(data, offset) {
return (data[offset] << 24) | (data[offset + 1] << 16) |
(data[offset + 2] << 8) | data[offset + 3];
}
function readUint16(data, offset) {
return (data[offset] << 8) | data[offset + 1];
}
function log2(x) {
var n = 1, i = 0;
while (x > n) {
n <<= 1;
i++;
}
return i;
}
function calculateComponentDimensions(component, siz) {
// Section B.2 Component mapping
component.x0 = Math.ceil(siz.XOsiz / component.XRsiz);
component.x1 = Math.ceil(siz.Xsiz / component.XRsiz);
component.y0 = Math.ceil(siz.YOsiz / component.YRsiz);
component.y1 = Math.ceil(siz.Ysiz / component.YRsiz);
component.width = component.x1 - component.x0;
component.height = component.y1 - component.y0;
}
function calculateTileGrids(context, components) {
var siz = context.SIZ;
// Section B.3 Division into tile and tile-components
var tiles = [];
var numXtiles = Math.ceil((siz.Xsiz - siz.XTOsiz) / siz.XTsiz);
var numYtiles = Math.ceil((siz.Ysiz - siz.YTOsiz) / siz.YTsiz);
for (var q = 0; q < numYtiles; q++) {
for (var p = 0; p < numXtiles; p++) {
var tile = {};
tile.tx0 = Math.max(siz.XTOsiz + p * siz.XTsiz, siz.XOsiz);
tile.ty0 = Math.max(siz.YTOsiz + q * siz.YTsiz, siz.YOsiz);
tile.tx1 = Math.min(siz.XTOsiz + (p + 1) * siz.XTsiz, siz.Xsiz);
tile.ty1 = Math.min(siz.YTOsiz + (q + 1) * siz.YTsiz, siz.Ysiz);
tile.width = tile.tx1 - tile.tx0;
tile.height = tile.ty1 - tile.ty0;
tile.components = [];
tiles.push(tile);
}
}
context.tiles = tiles;
var componentsCount = siz.Csiz;
for (var i = 0, ii = componentsCount; i < ii; i++) {
var component = components[i];
var tileComponents = [];
for (var j = 0, jj = tiles.length; j < jj; j++) {
var tileComponent = {}, tile = tiles[j];
tileComponent.tcx0 = Math.ceil(tile.tx0 / component.XRsiz);
tileComponent.tcy0 = Math.ceil(tile.ty0 / component.YRsiz);
tileComponent.tcx1 = Math.ceil(tile.tx1 / component.XRsiz);
tileComponent.tcy1 = Math.ceil(tile.ty1 / component.YRsiz);
tileComponent.width = tileComponent.tcx1 - tileComponent.tcx0;
tileComponent.height = tileComponent.tcy1 - tileComponent.tcy0;
tile.components[i] = tileComponent;
}
}
}
function getBlocksDimensions(context, component, r) {
var codOrCoc = component.codingStyleParameters;
var result = {};
if (!codOrCoc.entropyCoderWithCustomPrecincts) {
result.PPx = 15;
result.PPy = 15;
} else {
result.PPx = codOrCoc.precinctsSizes[r].PPx;
result.PPy = codOrCoc.precinctsSizes[r].PPy;
}
// calculate codeblock size as described in section B.7
result.xcb_ = r > 0 ? Math.min(codOrCoc.xcb, result.PPx - 1) :
Math.min(codOrCoc.xcb, result.PPx);
result.ycb_ = r > 0 ? Math.min(codOrCoc.ycb, result.PPy - 1) :
Math.min(codOrCoc.ycb, result.PPy);
return result;
}
function buildPrecincts(context, resolution, dimensions) {
// Section B.6 Division resolution to precincts
var precinctWidth = 1 << dimensions.PPx;
var precinctHeight = 1 << dimensions.PPy;
var numprecinctswide = resolution.trx1 > resolution.trx0 ?
Math.ceil(resolution.trx1 / precinctWidth) -
Math.floor(resolution.trx0 / precinctWidth) : 0;
var numprecinctshigh = resolution.try1 > resolution.try0 ?
Math.ceil(resolution.try1 / precinctHeight) -
Math.floor(resolution.try0 / precinctHeight) : 0;
var numprecincts = numprecinctswide * numprecinctshigh;
var precinctXOffset = Math.floor(resolution.trx0 / precinctWidth) *
precinctWidth;
var precinctYOffset = Math.floor(resolution.try0 / precinctHeight) *
precinctHeight;
resolution.precinctParameters = {
precinctXOffset: precinctXOffset,
precinctYOffset: precinctYOffset,
precinctWidth: precinctWidth,
precinctHeight: precinctHeight,
numprecinctswide: numprecinctswide,
numprecinctshigh: numprecinctshigh,
numprecincts: numprecincts
};
}
function buildCodeblocks(context, subband, dimensions) {
// Section B.7 Division sub-band into code-blocks
var xcb_ = dimensions.xcb_;
var ycb_ = dimensions.ycb_;
var codeblockWidth = 1 << xcb_;
var codeblockHeight = 1 << ycb_;
var cbx0 = Math.floor(subband.tbx0 / codeblockWidth);
var cby0 = Math.floor(subband.tby0 / codeblockHeight);
var cbx1 = Math.ceil(subband.tbx1 / codeblockWidth);
var cby1 = Math.ceil(subband.tby1 / codeblockHeight);
var precinctParameters = subband.resolution.precinctParameters;
var codeblocks = [];
var precincts = [];
for (var j = cby0; j < cby1; j++) {
for (var i = cbx0; i < cbx1; i++) {
var codeblock = {
cbx: i,
cby: j,
tbx0: codeblockWidth * i,
tby0: codeblockHeight * j,
tbx1: codeblockWidth * (i + 1),
tby1: codeblockHeight * (j + 1)
};
// calculate precinct number
var pi = Math.floor((codeblock.tbx0 -
precinctParameters.precinctXOffset) /
precinctParameters.precinctWidth);
var pj = Math.floor((codeblock.tby0 -
precinctParameters.precinctYOffset) /
precinctParameters.precinctHeight);
var precinctNumber = pj +
pi * precinctParameters.numprecinctswide;
codeblock.tbx0_ = Math.max(subband.tbx0, codeblock.tbx0);
codeblock.tby0_ = Math.max(subband.tby0, codeblock.tby0);
codeblock.tbx1_ = Math.min(subband.tbx1, codeblock.tbx1);
codeblock.tby1_ = Math.min(subband.tby1, codeblock.tby1);
codeblock.precinctNumber = precinctNumber;
codeblock.subbandType = subband.type;
var coefficientsLength = (codeblock.tbx1_ - codeblock.tbx0_) *
(codeblock.tby1_ - codeblock.tby0_);
codeblock.Lblock = 3;
codeblocks.push(codeblock);
// building precinct for the sub-band
var precinct;
if (precinctNumber in precincts) {
precinct = precincts[precinctNumber];
precinct.cbxMin = Math.min(precinct.cbxMin, i);
precinct.cbyMin = Math.min(precinct.cbyMin, j);
precinct.cbxMax = Math.max(precinct.cbxMax, i);
precinct.cbyMax = Math.max(precinct.cbyMax, j);
} else {
precincts[precinctNumber] = precinct = {
cbxMin: i,
cbyMin: j,
cbxMax: i,
cbyMax: j
};
}
codeblock.precinct = precinct;
}
}
subband.codeblockParameters = {
codeblockWidth: xcb_,
codeblockHeight: ycb_,
numcodeblockwide: cbx1 - cbx0 + 1,
numcodeblockhigh: cby1 - cby1 + 1
};
subband.codeblocks = codeblocks;
for (var i = 0, ii = codeblocks.length; i < ii; i++) {
var codeblock = codeblocks[i];
var precinctNumber = codeblock.precinctNumber;
}
subband.precincts = precincts;
}
function createPacket(resolution, precinctNumber, layerNumber) {
var precinctCodeblocks = [];
// Section B.10.8 Order of info in packet
var subbands = resolution.subbands;
// sub-bands already ordered in 'LL', 'HL', 'LH', and 'HH' sequence
for (var i = 0, ii = subbands.length; i < ii; i++) {
var subband = subbands[i];
var codeblocks = subband.codeblocks;
for (var j = 0, jj = codeblocks.length; j < jj; j++) {
var codeblock = codeblocks[j];
if (codeblock.precinctNumber != precinctNumber)
continue;
precinctCodeblocks.push(codeblock);
}
}
return {
layerNumber: layerNumber,
codeblocks: precinctCodeblocks
};
}
function LayerResolutionComponentPositionIterator(context) {
var siz = context.SIZ;
var tileIndex = context.currentTile.index;
var tile = context.tiles[tileIndex];
var layersCount = tile.codingStyleDefaultParameters.layersCount;
var componentsCount = siz.Csiz;
var maxDecompositionLevelsCount = 0;
for (var q = 0; q < componentsCount; q++) {
maxDecompositionLevelsCount = Math.max(maxDecompositionLevelsCount,
tile.components[q].codingStyleParameters.decompositionLevelsCount);
}
var l = 0, r = 0, i = 0, k = 0;
this.nextPacket = function JpxImage_nextPacket() {
// Section B.12.1.1 Layer-resolution-component-position
for (; l < layersCount; l++) {
for (; r <= maxDecompositionLevelsCount; r++) {
for (; i < componentsCount; i++) {
var component = tile.components[i];
if (r > component.codingStyleParameters.decompositionLevelsCount)
continue;
var resolution = component.resolutions[r];
var numprecincts = resolution.precinctParameters.numprecincts;
for (; k < numprecincts;) {
var packet = createPacket(resolution, k, l);
k++;
return packet;
}
k = 0;
}
i = 0;
}
r = 0;
}
throw 'Out of packets';
};
}
function ResolutionLayerComponentPositionIterator(context) {
var siz = context.SIZ;
var tileIndex = context.currentTile.index;
var tile = context.tiles[tileIndex];
var layersCount = tile.codingStyleDefaultParameters.layersCount;
var componentsCount = siz.Csiz;
var maxDecompositionLevelsCount = 0;
for (var q = 0; q < componentsCount; q++) {
maxDecompositionLevelsCount = Math.max(maxDecompositionLevelsCount,
tile.components[q].codingStyleParameters.decompositionLevelsCount);
}
var r = 0, l = 0, i = 0, k = 0;
this.nextPacket = function JpxImage_nextPacket() {
// Section B.12.1.2 Resolution-layer-component-position
for (; r <= maxDecompositionLevelsCount; r++) {
for (; l < layersCount; l++) {
for (; i < componentsCount; i++) {
var component = tile.components[i];
if (r > component.codingStyleParameters.decompositionLevelsCount)
continue;
var resolution = component.resolutions[r];
var numprecincts = resolution.precinctParameters.numprecincts;
for (; k < numprecincts;) {
var packet = createPacket(resolution, k, l);
k++;
return packet;
}
k = 0;
}
i = 0;
}
l = 0;
}
throw 'Out of packets';
};
}
function buildPackets(context) {
var siz = context.SIZ;
var tileIndex = context.currentTile.index;
var tile = context.tiles[tileIndex];
var componentsCount = siz.Csiz;
// Creating resolutions and sub-bands for each component
for (var c = 0; c < componentsCount; c++) {
var component = tile.components[c];
var decompositionLevelsCount =
component.codingStyleParameters.decompositionLevelsCount;
// Section B.5 Resolution levels and sub-bands
var resolutions = [];
var subbands = [];
for (var r = 0; r <= decompositionLevelsCount; r++) {
var blocksDimensions = getBlocksDimensions(context, component, r);
var resolution = {};
var scale = 1 << (decompositionLevelsCount - r);
resolution.trx0 = Math.ceil(component.tcx0 / scale);
resolution.try0 = Math.ceil(component.tcy0 / scale);
resolution.trx1 = Math.ceil(component.tcx1 / scale);
resolution.try1 = Math.ceil(component.tcy1 / scale);
buildPrecincts(context, resolution, blocksDimensions);
resolutions.push(resolution);
var subband;
if (r === 0) {
// one sub-band (LL) with last decomposition
subband = {};
subband.type = 'LL';
subband.tbx0 = Math.ceil(component.tcx0 / scale);
subband.tby0 = Math.ceil(component.tcy0 / scale);
subband.tbx1 = Math.ceil(component.tcx1 / scale);
subband.tby1 = Math.ceil(component.tcy1 / scale);
subband.resolution = resolution;
buildCodeblocks(context, subband, blocksDimensions);
subbands.push(subband);
resolution.subbands = [subband];
} else {
var bscale = 1 << (decompositionLevelsCount - r + 1);
var resolutionSubbands = [];
// three sub-bands (HL, LH and HH) with rest of decompositions
subband = {};
subband.type = 'HL';
subband.tbx0 = Math.ceil(component.tcx0 / bscale - 0.5);
subband.tby0 = Math.ceil(component.tcy0 / bscale);
subband.tbx1 = Math.ceil(component.tcx1 / bscale - 0.5);
subband.tby1 = Math.ceil(component.tcy1 / bscale);
subband.resolution = resolution;
buildCodeblocks(context, subband, blocksDimensions);
subbands.push(subband);
resolutionSubbands.push(subband);
subband = {};
subband.type = 'LH';
subband.tbx0 = Math.ceil(component.tcx0 / bscale);
subband.tby0 = Math.ceil(component.tcy0 / bscale - 0.5);
subband.tbx1 = Math.ceil(component.tcx1 / bscale);
subband.tby1 = Math.ceil(component.tcy1 / bscale - 0.5);
subband.resolution = resolution;
buildCodeblocks(context, subband, blocksDimensions);
subbands.push(subband);
resolutionSubbands.push(subband);
subband = {};
subband.type = 'HH';
subband.tbx0 = Math.ceil(component.tcx0 / bscale - 0.5);
subband.tby0 = Math.ceil(component.tcy0 / bscale - 0.5);
subband.tbx1 = Math.ceil(component.tcx1 / bscale - 0.5);
subband.tby1 = Math.ceil(component.tcy1 / bscale - 0.5);
subband.resolution = resolution;
buildCodeblocks(context, subband, blocksDimensions);
subbands.push(subband);
resolutionSubbands.push(subband);
resolution.subbands = resolutionSubbands;
}
}
component.resolutions = resolutions;
component.subbands = subbands;
}
// Generate the packets sequence
var progressionOrder = tile.codingStyleDefaultParameters.progressionOrder;
var packetsIterator;
switch (progressionOrder) {
case 0:
tile.packetsIterator =
new LayerResolutionComponentPositionIterator(context);
break;
case 1:
tile.packetsIterator =
new ResolutionLayerComponentPositionIterator(context);
break;
default:
throw 'Unsupported progression order ' + progressionOrder;
}
}
function parseTilePackets(context, data, offset, dataLength) {
var position = 0;
var buffer, bufferSize = 0, skipNextBit = false;
function readBits(count) {
while (bufferSize < count) {
var b = data[offset + position];
position++;
if (skipNextBit) {
buffer = (buffer << 7) | b;
bufferSize += 7;
skipNextBit = false;
} else {
buffer = (buffer << 8) | b;
bufferSize += 8;
}
if (b == 0xFF) {
skipNextBit = true;
}
}
bufferSize -= count;
return (buffer >>> bufferSize) & ((1 << count) - 1);
}
function alignToByte() {
bufferSize = 0;
if (skipNextBit) {
position++;
skipNextBit = false;
}
}
function readCodingpasses() {
var value = readBits(1);
if (value === 0)
return 1;
value = (value << 1) | readBits(1);
if (value == 0x02)
return 2;
value = (value << 2) | readBits(2);
if (value <= 0x0E)
return (value & 0x03) + 3;
value = (value << 5) | readBits(5);
if (value <= 0x1FE)
return (value & 0x1F) + 6;
value = (value << 7) | readBits(7);
return (value & 0x7F) + 37;
}
var tileIndex = context.currentTile.index;
var tile = context.tiles[tileIndex];
var packetsIterator = tile.packetsIterator;
while (position < dataLength) {
var packet = packetsIterator.nextPacket();
if (!readBits(1)) {
alignToByte();
continue;
}
var layerNumber = packet.layerNumber;
var queue = [];
for (var i = 0, ii = packet.codeblocks.length; i < ii; i++) {
var codeblock = packet.codeblocks[i];
var precinct = codeblock.precinct;
var codeblockColumn = codeblock.cbx - precinct.cbxMin;
var codeblockRow = codeblock.cby - precinct.cbyMin;
var codeblockIncluded = false;
var firstTimeInclusion = false;
if ('included' in codeblock) {
codeblockIncluded = !!readBits(1);
} else {
// reading inclusion tree
var precinct = codeblock.precinct;
var inclusionTree, zeroBitPlanesTree;
if ('inclusionTree' in precinct) {
inclusionTree = precinct.inclusionTree;
} else {
// building inclusion and zero bit-planes trees
var width = precinct.cbxMax - precinct.cbxMin + 1;
var height = precinct.cbyMax - precinct.cbyMin + 1;
inclusionTree = new InclusionTree(width, height, layerNumber);
zeroBitPlanesTree = new TagTree(width, height);
precinct.inclusionTree = inclusionTree;
precinct.zeroBitPlanesTree = zeroBitPlanesTree;
}
if (inclusionTree.reset(codeblockColumn, codeblockRow, layerNumber)) {
while (true) {
if (readBits(1)) {
var valueReady = !inclusionTree.nextLevel();
if (valueReady) {
codeblock.included = true;
codeblockIncluded = firstTimeInclusion = true;
break;
}
} else {
inclusionTree.incrementValue(layerNumber);
break;
}
}
}
}
if (!codeblockIncluded)
continue;
if (firstTimeInclusion) {
zeroBitPlanesTree = precinct.zeroBitPlanesTree;
zeroBitPlanesTree.reset(codeblockColumn, codeblockRow);
while (true) {
if (readBits(1)) {
var valueReady = !zeroBitPlanesTree.nextLevel();
if (valueReady)
break;
} else
zeroBitPlanesTree.incrementValue();
}
codeblock.zeroBitPlanes = zeroBitPlanesTree.value;
}
var codingpasses = readCodingpasses();
while (readBits(1))
codeblock.Lblock++;
var codingpassesLog2 = log2(codingpasses);
// rounding down log2
var bits = ((codingpasses < (1 << codingpassesLog2)) ?
codingpassesLog2 - 1 : codingpassesLog2) + codeblock.Lblock;
var codedDataLength = readBits(bits);
queue.push({
codeblock: codeblock,
codingpasses: codingpasses,
dataLength: codedDataLength
});
}
alignToByte();
while (queue.length > 0) {
var packetItem = queue.shift();
var codeblock = packetItem.codeblock;
if (!('data' in codeblock))
codeblock.data = [];
codeblock.data.push({
data: data,
start: offset + position,
end: offset + position + packetItem.dataLength,
codingpasses: packetItem.codingpasses
});
position += packetItem.dataLength;
}
}
return position;
}
function copyCoefficients(coefficients, x0, y0, width, height,
delta, mb, codeblocks, transformation,
segmentationSymbolUsed) {
var r = 0.5; // formula (E-6)
for (var i = 0, ii = codeblocks.length; i < ii; ++i) {
var codeblock = codeblocks[i];
var blockWidth = codeblock.tbx1_ - codeblock.tbx0_;
var blockHeight = codeblock.tby1_ - codeblock.tby0_;
if (blockWidth === 0 || blockHeight === 0)
continue;
if (!('data' in codeblock))
continue;
var bitModel, currentCodingpassType;
bitModel = new BitModel(blockWidth, blockHeight, codeblock.subbandType,
codeblock.zeroBitPlanes);
currentCodingpassType = 2; // first bit plane starts from cleanup
// collect data
var data = codeblock.data, totalLength = 0, codingpasses = 0;
for (var q = 0, qq = data.length; q < qq; q++) {
var dataItem = data[q];
totalLength += dataItem.end - dataItem.start;
codingpasses += dataItem.codingpasses;
}
var encodedData = new Uint8Array(totalLength), k = 0;
for (var q = 0, qq = data.length; q < qq; q++) {
var dataItem = data[q];
var chunk = dataItem.data.subarray(dataItem.start, dataItem.end);
encodedData.set(chunk, k);
k += chunk.length;
}
// decoding the item
var decoder = new ArithmeticDecoder(encodedData, 0, totalLength);
bitModel.setDecoder(decoder);
for (var q = 0; q < codingpasses; q++) {
switch (currentCodingpassType) {
case 0:
bitModel.runSignificancePropogationPass();
break;
case 1:
bitModel.runMagnitudeRefinementPass();
break;
case 2:
bitModel.runCleanupPass();
if (segmentationSymbolUsed)
bitModel.checkSegmentationSymbol();
break;
}
currentCodingpassType = (currentCodingpassType + 1) % 3;
}
var offset = (codeblock.tbx0_ - x0) + (codeblock.tby0_ - y0) * width;
var position = 0;
for (var j = 0; j < blockHeight; j++) {
for (var k = 0; k < blockWidth; k++) {
var n = (bitModel.coefficentsSign[position] ? -1 : 1) *
bitModel.coefficentsMagnitude[position];
var nb = bitModel.bitsDecoded[position], correction;
if (transformation === 0 || mb > nb) {
// use r only if transformation is irreversible or
// not all bitplanes were decoded for reversible transformation
n += n < 0 ? n - r : n > 0 ? n + r : 0;
correction = 1 << (mb - nb);
} else
correction = 1;
coefficients[offset++] = n * correction * delta;
position++;
}
offset += width - blockWidth;
}
}
}
function transformTile(context, tile, c) {
var component = tile.components[c];
var codingStyleParameters = component.codingStyleParameters;
var quantizationParameters = component.quantizationParameters;
var decompositionLevelsCount =
codingStyleParameters.decompositionLevelsCount;
var spqcds = quantizationParameters.SPqcds;
var scalarExpounded = quantizationParameters.scalarExpounded;
var guardBits = quantizationParameters.guardBits;
var transformation = codingStyleParameters.transformation;
var segmentationSymbolUsed = codingStyleParameters.segmentationSymbolUsed;
var precision = context.components[c].precision;
var subbandCoefficients = [];
var k = 0, b = 0;
for (var i = 0; i <= decompositionLevelsCount; i++) {
var resolution = component.resolutions[i];
for (var j = 0, jj = resolution.subbands.length; j < jj; j++) {
var mu, epsilon;
if (!scalarExpounded) {
// formula E-5
mu = spqcds[0].mu;
epsilon = spqcds[0].epsilon + (i > 0 ? 1 - i : 0);
} else {
mu = spqcds[b].mu;
epsilon = spqcds[b].epsilon;
}
var subband = resolution.subbands[j];
var width = subband.tbx1 - subband.tbx0;
var height = subband.tby1 - subband.tby0;
var gainLog2 = SubbandsGainLog2[subband.type];
// calulate quantization coefficient (Section E.1.1.1)
var delta = Math.pow(2, (precision + gainLog2) - epsilon) *
(1 + mu / 2048);
var mb = (guardBits + epsilon - 1);
var coefficients = new Float32Array(width * height);
copyCoefficients(coefficients, subband.tbx0, subband.tby0,
width, height, delta, mb, subband.codeblocks, transformation,
segmentationSymbolUsed);
subbandCoefficients.push({
width: width,
height: height,
items: coefficients
});
b++;
}
}
var transformation = codingStyleParameters.transformation;
var transform = transformation === 0 ? new IrreversibleTransform() :
new ReversibleTransform();
var result = transform.calculate(subbandCoefficients,
component.tcx0, component.tcy0);
return {
left: component.tcx0,
top: component.tcy0,
width: result.width,
height: result.height,
items: result.items
};
}
function transformComponents(context) {
var siz = context.SIZ;
var components = context.components;
var componentsCount = siz.Csiz;
var resultImages = [];
for (var i = 0, ii = context.tiles.length; i < ii; i++) {
var tile = context.tiles[i];
var result = [];
for (var c = 0; c < componentsCount; c++) {
var image = transformTile(context, tile, c);
result.push(image);