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Faster JPX decoding

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This commit is contained in:
fkaelberer 2014-02-24 18:43:12 +01:00
parent f11a6ae238
commit 5f8546c120
1 changed files with 66 additions and 42 deletions
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108
src/core/jpx.js
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@ -1692,18 +1692,18 @@ var JpxImage = (function JpxImageClosure() {
}
return ll;
};
Transform.prototype.expand = function expand(buffer, bufferPadding, step) {
Transform.prototype.extend = function extend(buffer, offset, size) {
// Section F.3.7 extending... using max extension of 4
var i1 = bufferPadding - 1, j1 = bufferPadding + 1;
var i2 = bufferPadding + step - 2, j2 = bufferPadding + step;
buffer[i1--] = buffer[j1++];
buffer[j2++] = buffer[i2--];
var i1 = offset - 1, j1 = offset + 1;
var i2 = offset + size - 2, j2 = offset + size;
buffer[i1--] = buffer[j1++];
buffer[j2++] = buffer[i2--];
buffer[i1--] = buffer[j1++];
buffer[j2++] = buffer[i2--];
buffer[i1--] = buffer[j1++];
buffer[j2++] = buffer[i2--];
buffer[i1] = buffer[j1];
buffer[j2] = buffer[i2];
};
Transform.prototype.iterate = function Transform_iterate(ll, hl, lh, hh,
u0, v0) {
@ -1716,32 +1716,35 @@ var JpxImage = (function JpxImageClosure() {
var width = llWidth + hlWidth;
var height = llHeight + lhHeight;
var items = new Float32Array(width * height);
for (var i = 0, ii = llHeight; i < ii; i++) {
var i, j, k, l;
for (i = 0; i < llHeight; i++) {
var k = i * llWidth, l = i * 2 * width;
for (var j = 0, jj = llWidth; j < jj; j++, k++, l += 2)
for (var j = 0; j < llWidth; j++, k++, l += 2) {
items[l] = llItems[k];
}
}
for (var i = 0, ii = hlHeight; i < ii; i++) {
var k = i * hlWidth, l = i * 2 * width + 1;
for (var j = 0, jj = hlWidth; j < jj; j++, k++, l += 2)
for (i = 0; i < hlHeight; i++) {
k = i * hlWidth, l = i * 2 * width + 1;
for (j = 0; j < hlWidth; j++, k++, l += 2) {
items[l] = hlItems[k];
}
}
for (var i = 0, ii = lhHeight; i < ii; i++) {
var k = i * lhWidth, l = (i * 2 + 1) * width;
for (var j = 0, jj = lhWidth; j < jj; j++, k++, l += 2)
for (i = 0; i < lhHeight; i++) {
k = i * lhWidth, l = (i * 2 + 1) * width;
for (j = 0; j < lhWidth; j++, k++, l += 2) {
items[l] = lhItems[k];
}
}
for (var i = 0, ii = hhHeight; i < ii; i++) {
var k = i * hhWidth, l = (i * 2 + 1) * width + 1;
for (var j = 0, jj = hhWidth; j < jj; j++, k++, l += 2)
for (i = 0; i < hhHeight; i++) {
k = i * hhWidth, l = (i * 2 + 1) * width + 1;
for (j = 0; j < hhWidth; j++, k++, l += 2) {
items[l] = hhItems[k];
}
}
var bufferPadding = 4;
var bufferLength = new Float32Array(Math.max(width, height) +
2 * bufferPadding);
var buffer = new Float32Array(bufferLength);
var bufferOut = new Float32Array(bufferLength);
var rowBuffer = new Float32Array(width + 2 * bufferPadding);
// Section F.3.4 HOR_SR
for (var v = 0; v < height; v++) {
@ -1752,21 +1755,28 @@ var JpxImage = (function JpxImageClosure() {
}
continue;
}
var k = v * width;
var l = bufferPadding;
for (var u = 0; u < width; u++, k++, l++)
buffer[l] = items[k];
this.expand(buffer, bufferPadding, width);
this.filter(buffer, bufferPadding, width, u0, bufferOut);
k = v * width;
l = bufferPadding;
for (var u = 0; u < width; u++, k++, l++)
items[k] = bufferOut[l];
rowBuffer.set(items.subarray(k, k + width), bufferPadding);
this.extend(rowBuffer, bufferPadding, width);
this.filter(rowBuffer, bufferPadding, width, u0, rowBuffer);
items.set(rowBuffer.subarray(bufferPadding, bufferPadding + width), k);
}
// Accesses to the items array can take long, because it may not fit into
// CPU cache and has to be fetched from main memory. Since subsequent
// accesses to the items array are not local when reading columns, we
// have a cache miss every time. To reduce cache misses, get up to
// 'numBuffers' items at a time and store them into the individual
// buffers. The colBuffers should be small enough to fit into CPU cache.
var numBuffers = 16;
var colBuffers = [];
for (i = 0; i < numBuffers; i++) {
colBuffers.push(new Float32Array(height + 2 * bufferPadding));
}
var b, currentBuffer = 0, ll = bufferPadding + height;
// Section F.3.5 VER_SR
for (var u = 0; u < width; u++) {
if (height == 1) {
@ -1777,19 +1787,33 @@ var JpxImage = (function JpxImageClosure() {
continue;
}
var k = u;
var l = bufferPadding;
for (var v = 0; v < height; v++, k += width, l++)
buffer[l] = items[k];
// if we ran out of buffers, copy several image columns at once
if (currentBuffer === 0) {
numBuffers = Math.min(width - u, numBuffers);
for (k = u, l = bufferPadding; l < ll; k += width, l++) {
for (b = 0; b < numBuffers; b++) {
colBuffers[b][l] = items[k + b];
}
}
currentBuffer = numBuffers;
}
this.expand(buffer, bufferPadding, height);
this.filter(buffer, bufferPadding, height, v0, bufferOut);
currentBuffer--;
var buffer = colBuffers[currentBuffer];
this.extend(buffer, bufferPadding, height);
this.filter(buffer, bufferPadding, height, v0, buffer);
k = u;
l = bufferPadding;
for (var v = 0; v < height; v++, k += width, l++)
items[k] = bufferOut[l];
// If this is last buffer in this group of buffers, flush all buffers.
if (currentBuffer === 0) {
k = u - numBuffers + 1;
for (l = bufferPadding; l < ll; k += width, l++) {
for (b = 0; b < numBuffers; b++) {
items[k + b] = colBuffers[b][l];
}
}
}
}
return {
width: width,
height: height,