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Merge pull request #4434 from p01/jbig2Optimizations
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Jbig2 optimizations
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@yurydelendik
yurydelendik committed Mar 14, 2014
2 parents ba8a590 + bd9419f commit 8266225
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Showing 2 changed files with 91 additions and 56 deletions.
37 changes: 18 additions & 19 deletions src/core/arithmetic_decoder.js
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Original file line number Diff line number Diff line change
Expand Up @@ -128,41 +128,39 @@ var ArithmeticDecoder = (function ArithmeticDecoderClosure() {
var cx_index = contexts[pos] >> 1, cx_mps = contexts[pos] & 1;
var qeTableIcx = QeTable[cx_index];
var qeIcx = qeTableIcx.qe;
var nmpsIcx = qeTableIcx.nmps;
var nlpsIcx = qeTableIcx.nlps;
var switchIcx = qeTableIcx.switchFlag;
var d;
this.a -= qeIcx;
var a = this.a - qeIcx;

if (this.chigh < qeIcx) {
// exchangeLps
if (this.a < qeIcx) {
this.a = qeIcx;
if (a < qeIcx) {
a = qeIcx;
d = cx_mps;
cx_index = nmpsIcx;
cx_index = qeTableIcx.nmps;
} else {
this.a = qeIcx;
d = 1 - cx_mps;
if (switchIcx) {
a = qeIcx;
d = 1 ^ cx_mps;
if (qeTableIcx.switchFlag === 1) {
cx_mps = d;
}
cx_index = nlpsIcx;
cx_index = qeTableIcx.nlps;
}
} else {
this.chigh -= qeIcx;
if ((this.a & 0x8000) !== 0) {
if ((a & 0x8000) !== 0) {
this.a = a;
return cx_mps;
}
// exchangeMps
if (this.a < qeIcx) {
d = 1 - cx_mps;
if (switchIcx) {
if (a < qeIcx) {
d = 1 ^ cx_mps;
if (qeTableIcx.switchFlag === 1) {
cx_mps = d;
}
cx_index = nlpsIcx;
cx_index = qeTableIcx.nlps;
} else {
d = cx_mps;
cx_index = nmpsIcx;
cx_index = qeTableIcx.nmps;
}
}
// C.3.3 renormD;
Expand All @@ -171,11 +169,12 @@ var ArithmeticDecoder = (function ArithmeticDecoderClosure() {
this.byteIn();
}

this.a <<= 1;
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);
} while ((a & 0x8000) === 0);
this.a = a;

contexts[pos] = cx_index << 1 | cx_mps;
return d;
Expand Down
110 changes: 73 additions & 37 deletions src/core/jbig2.js
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Original file line number Diff line number Diff line change
Expand Up @@ -105,7 +105,7 @@ var Jbig2Image = (function Jbig2ImageClosure() {
offset = 340;
break;
default:
v = v * 2 + bit;
v = ((v << 1) | bit) >>> 0;
if (--toRead === 0) {
state = 0;
}
Expand All @@ -124,12 +124,12 @@ var Jbig2Image = (function Jbig2ImageClosure() {
var prev = 1;
for (var i = 0; i < codeLength; i++) {
var bit = decoder.readBit(contexts, prev);
prev = (prev * 2) + bit;
prev = (prev << 1) | bit;
}
if (codeLength < 31) {
return prev & ((1 << codeLength) - 1);
}
return prev - Math.pow(2, codeLength);
return prev & 0x7FFFFFFF;
}

// 7.3 Segment types
Expand Down Expand Up @@ -255,26 +255,41 @@ var Jbig2Image = (function Jbig2ImageClosure() {
changingTemplateEntries.push(k);
}
}
changingTemplateEntries = new Uint8Array(changingTemplateEntries);
var changingEntriesLength = changingTemplateEntries.length;

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

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

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

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

var ltp = 0, c, j, i0, j0, k, contextLabel = 0;
var ltp = 0, c, j, i0, j0, k, contextLabel = 0, bit, shift;
for (var i = 0; i < height; i++) {
if (prediction) {
var sltp = decoder.readBit(contexts, pseudoPixelContext);
ltp ^= sltp;
if (ltp) {
bitmap.push(row); // duplicate previous row
continue;
}
}
if (ltp) {
bitmap.push(bitmap[bitmap.length - 1]); // duplicate previous row
continue;
}
var row = new Uint8Array(width);
row = new Uint8Array(row);
bitmap.push(row);
for (j = 0; j < width; j++) {
if (useskip && skip[i][j]) {
Expand All @@ -283,24 +298,33 @@ var Jbig2Image = (function Jbig2ImageClosure() {
}
// Are we in the middle of a scanline, so we can reuse contextLabel
// bits?
if (i + minY > 0 && j + minX >= 0 && j + maxX < width) {
if (j >= sbb_left && j < sbb_right && i >= sbb_top) {
// If yes, we can just shift the bits that are reusable and only
// fetch the remaining ones.
contextLabel = (contextLabel << 1) & reuseMask;
for (c = 0; c < changingEntriesLength; c++) {
k = changingTemplateEntries[c];
i0 = i + templateY[k];
j0 = j + templateX[k];
contextLabel |= bitmap[i0][j0] << (templateLength - 1 - k);
for (k = 0; k < changingEntriesLength; k++) {
i0 = i + changingTemplateY[k];
j0 = j + changingTemplateX[k];
bit = bitmap[i0][j0];
if (bit) {
bit = changingTemplateBit[k];
contextLabel |= bit;
}
}
} else {
// compute the contextLabel from scratch
contextLabel = 0;
for (k = 0; k < templateLength; k++) {
i0 = i + templateY[k];
shift = templateLength - 1;
for (k = 0; k < templateLength; k++, shift--) {
j0 = j + templateX[k];
if (i0 >= 0 && j0 >= 0 && j0 < width) {
contextLabel |= bitmap[i0][j0] << (templateLength - 1 - k);
if (j0 >= 0 && j0 < width) {
i0 = i + templateY[k];
if (i0 >= 0) {
bit = bitmap[i0][j0];
if (bit) {
contextLabel |= bit << shift;
}
}
}
}
}
Expand Down Expand Up @@ -352,13 +376,13 @@ var Jbig2Image = (function Jbig2ImageClosure() {
if (prediction) {
var sltp = decoder.readBit(contexts, pseudoPixelContext);
ltp ^= sltp;
if (ltp) {
error('JBIG2 error: prediction is not supported');
}
}
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++) {
Expand Down Expand Up @@ -938,34 +962,46 @@ var Jbig2Image = (function Jbig2ImageClosure() {
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
var mask0 = 128 >> (regionInfo.x & 7);
var offset0 = regionInfo.y * rowSize + (regionInfo.x >> 3);
switch (combinationOperator) {
case 0: // OR
for (var i = 0; i < height; i++) {
var mask = mask0;
var offset = offset0;
for (var j = 0; j < width; j++) {
buffer[offset] |= bitmap[i][j] ? mask : 0;
if (bitmap[i][j]) {
buffer[offset] |= mask;
}
mask >>= 1;
if (!mask) {
mask = 128;
offset++;
}
}
break;
case 2: // XOR
offset0 += rowSize;
}
break;
case 2: // XOR
for (var i = 0; i < height; i++) {
var mask = mask0;
var offset = offset0;
for (var j = 0; j < width; j++) {
buffer[offset] ^= bitmap[i][j] ? mask : 0;
if (bitmap[i][j]) {
buffer[offset] ^= mask;
}
mask >>= 1;
if (!mask) {
mask = 128;
offset++;
}
}
break;
default:
error('JBIG2 error: operator ' + combinationOperator +
' is not supported');
}
offset0 += rowSize;
}
break;
default:
error('JBIG2 error: operator ' + combinationOperator +
' is not supported');
}
},
onImmediateGenericRegion:
Expand Down

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