[Pkg-javascript-commits] [pdf.js] 46/56: Optimized JPX decoder ~6% faster
David Prévot
taffit at moszumanska.debian.org
Thu May 15 15:17:46 UTC 2014
This is an automated email from the git hooks/post-receive script.
taffit pushed a commit to branch master
in repository pdf.js.
commit a66326cc5449437297bf4c5d8096671d1b1a3fd5
Author: p01 <p01 at opera.com>
Date: Thu Apr 10 15:07:50 2014 +0200
Optimized JPX decoder ~6% faster
---
src/core/jpx.js | 108 +++++++++++++++++++++++++++++++++++++++-----------------
1 file changed, 75 insertions(+), 33 deletions(-)
diff --git a/src/core/jpx.js b/src/core/jpx.js
index 4c4294b..8c2efdd 100644
--- a/src/core/jpx.js
+++ b/src/core/jpx.js
@@ -954,7 +954,7 @@ var JpxImage = (function JpxImageClosure() {
var magnitudeCorrection = reversible ? 0 : 0.5;
var k, n, nb;
position = 0;
- // Do the interleaving of Section F.3.3 here, so we do not need
+ // Do the interleaving of Section F.3.3 here, so we do not need
// to copy later. LL level is not interleaved, just copied.
var interleave = (subband.type !== 'LL');
for (j = 0; j < blockHeight; j++) {
@@ -1566,12 +1566,16 @@ var JpxImage = (function JpxImageClosure() {
var oneRowDown = width;
var twoRowsDown = width * 2;
var threeRowsDown = width * 3;
- for (var i0 = 0; i0 < height; i0 += 4) {
+ var iNext;
+ for (var i0 = 0; i0 < height; i0 = iNext) {
+ iNext = Math.min(i0 + 4, height);
+ var indexBase = i0 * width;
+ var checkAllEmpty = i0 + 3 < height;
for (var j = 0; j < width; j++) {
- var index0 = i0 * width + j;
+ var index0 = indexBase + j;
// using the property: labels[neighborsSignificance[index]] == 0
// when neighborsSignificance[index] == 0
- var allEmpty = (i0 + 3 < height &&
+ var allEmpty = (checkAllEmpty &&
processingFlags[index0] === 0 &&
processingFlags[index0 + oneRowDown] === 0 &&
processingFlags[index0 + twoRowsDown] === 0 &&
@@ -1581,7 +1585,7 @@ var JpxImage = (function JpxImageClosure() {
neighborsSignificance[index0 + twoRowsDown] === 0 &&
neighborsSignificance[index0 + threeRowsDown] === 0);
var i1 = 0, index = index0;
- var i, sign;
+ var i = i0, sign;
if (allEmpty) {
var hasSignificantCoefficent =
decoder.readBit(contexts, RUNLENGTH_CONTEXT);
@@ -1594,8 +1598,10 @@ var JpxImage = (function JpxImageClosure() {
}
i1 = (decoder.readBit(contexts, UNIFORM_CONTEXT) << 1) |
decoder.readBit(contexts, UNIFORM_CONTEXT);
- i = i0 + i1;
- index += i1 * width;
+ if (i1 !== 0) {
+ i = i0 + i1;
+ index += i1 * width;
+ }
sign = this.decodeSignBit(i, j, index);
coefficentsSign[index] = sign;
@@ -1610,12 +1616,7 @@ var JpxImage = (function JpxImageClosure() {
i1++;
}
- for (; i1 < 4; i1++, index += width) {
- i = i0 + i1;
- if (i >= height) {
- break;
- }
-
+ for (i = i0 + i1; i < iNext; i++, index += width) {
if (coefficentsMagnitude[index] ||
(processingFlags[index] & processedMask) !== 0) {
continue;
@@ -1623,7 +1624,7 @@ var JpxImage = (function JpxImageClosure() {
var contextLabel = labels[neighborsSignificance[index]];
var decision = decoder.readBit(contexts, contextLabel);
- if (decision == 1) {
+ if (decision === 1) {
sign = this.decodeSignBit(i, j, index);
coefficentsSign[index] = sign;
coefficentsMagnitude[index] = 1;
@@ -1678,7 +1679,6 @@ var JpxImage = (function JpxImageClosure() {
};
Transform.prototype.iterate = function Transform_iterate(ll, hl_lh_hh,
u0, v0) {
-
var llWidth = ll.width, llHeight = ll.height, llItems = ll.items;
var width = hl_lh_hh.width;
var height = hl_lh_hh.height;
@@ -1711,7 +1711,7 @@ var JpxImage = (function JpxImageClosure() {
rowBuffer.set(items.subarray(k, k + width), bufferPadding);
this.extend(rowBuffer, bufferPadding, width);
- this.filter(rowBuffer, bufferPadding, width, u0, rowBuffer);
+ this.filter(rowBuffer, bufferPadding, width);
items.set(
rowBuffer.subarray(bufferPadding, bufferPadding + width),
@@ -1757,7 +1757,7 @@ var JpxImage = (function JpxImageClosure() {
currentBuffer--;
var buffer = colBuffers[currentBuffer];
this.extend(buffer, bufferPadding, height);
- this.filter(buffer, bufferPadding, height, v0, buffer);
+ this.filter(buffer, bufferPadding, height);
// If this is last buffer in this group of buffers, flush all buffers.
if (currentBuffer === 0) {
@@ -1788,9 +1788,10 @@ var JpxImage = (function JpxImageClosure() {
IrreversibleTransform.prototype = Object.create(Transform.prototype);
IrreversibleTransform.prototype.filter =
- function irreversibleTransformFilter(y, offset, length, i0, x) {
+ function irreversibleTransformFilter(x, offset, length) {
var len = length >> 1;
offset = offset | 0;
+ var j, n, current, next;
var alpha = -1.586134342059924;
var beta = -0.052980118572961;
@@ -1798,34 +1799,75 @@ var JpxImage = (function JpxImageClosure() {
var delta = 0.443506852043971;
var K = 1.230174104914001;
var K_ = 1 / K;
- var j, n;
// step 1 is combined with step 3
// step 2
- for (j = offset - 3, n = len + 4; n--; j += 2) {
- x[j] = K_ * y[j];
+ j = offset - 3;
+ for (n = len + 4; n--; j += 2) {
+ x[j] *= K_;
}
// step 1 & 3
- for (j = offset - 2, n = len + 3; n--; j += 2) {
- x[j] = K * y[j] -
- delta * (x[j - 1] + x[j + 1]);
+ j = offset - 2;
+ current = delta * x[j -1];
+ for (n = len + 3; n--; j += 2) {
+ next = delta * x[j + 1];
+ x[j] = K * x[j] - current - next;
+ if (n--) {
+ j += 2;
+ current = delta * x[j + 1];
+ x[j] = K * x[j] - current - next;
+ } else {
+ break;
+ }
}
// step 4
- for (j = offset - 1, n = len + 2; n--; j += 2) {
- x[j] -= gamma * (x[j - 1] + x[j + 1]);
+ j = offset - 1;
+ current = gamma * x[j - 1];
+ for (n = len + 2; n--; j += 2) {
+ next = gamma * x[j + 1];
+ x[j] -= current + next;
+ if (n--) {
+ j += 2;
+ current = gamma * x[j + 1];
+ x[j] -= current + next;
+ } else {
+ break;
+ }
}
// step 5
- for (j = offset, n = len + 1; n--; j += 2) {
- x[j] -= beta * (x[j - 1] + x[j + 1]);
+ j = offset;
+ current = beta * x[j - 1];
+ for (n = len + 1; n--; j += 2) {
+ next = beta * x[j + 1];
+ x[j] -= current + next;
+ if (n--) {
+ j += 2;
+ current = beta * x[j + 1];
+ x[j] -= current + next;
+ } else {
+ break;
+ }
}
// step 6
- for (j = offset + 1, n = len; n--; j += 2) {
- x[j] -= alpha * (x[j - 1] + x[j + 1]);
+ if (len !== 0) {
+ j = offset + 1;
+ current = alpha * x[j - 1];
+ for (n = len; n--; j += 2) {
+ next = alpha * x[j + 1];
+ x[j] -= current + next;
+ if (n--) {
+ j += 2;
+ current = alpha * x[j + 1];
+ x[j] -= current + next;
+ } else {
+ break;
+ }
+ }
}
};
@@ -1840,17 +1882,17 @@ var JpxImage = (function JpxImageClosure() {
ReversibleTransform.prototype = Object.create(Transform.prototype);
ReversibleTransform.prototype.filter =
- function reversibleTransformFilter(y, offset, length, i0, x) {
+ function reversibleTransformFilter(x, offset, length) {
var len = length >> 1;
offset = offset | 0;
var j, n;
for (j = offset, n = len + 1; n--; j += 2) {
- x[j] = y[j] - ((y[j - 1] + y[j + 1] + 2) >> 2);
+ x[j] -= (x[j - 1] + x[j + 1] + 2) >> 2;
}
for (j = offset + 1, n = len; n--; j += 2) {
- x[j] = y[j] + ((x[j - 1] + x[j + 1]) >> 1);
+ x[j] += (x[j - 1] + x[j + 1]) >> 1;
}
};
--
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