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jpgjs performance improvements 

see https://github.com/notmasteryet/jpgjs/pull/22
Thorben Bochenek 11 years ago committed by Yury Delendik
parent
1416eca164
commit
03892a85c2
1 changed files with 234 additions and 227 deletions
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  1. 459
      external/jpgjs/jpg.js

459
external/jpgjs/jpg.js vendored
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@ -88,6 +88,10 @@ var JpegImage = (function jpegImage() {
return code[0].children; return code[0].children;
} }
function getBlockBufferOffset(component, row, col) {
return 64 * (component.blocksPerLine * row + col);
}
function decodeScan(data, offset, function decodeScan(data, offset,
frame, components, resetInterval, frame, components, resetInterval,
spectralStart, spectralEnd, spectralStart, spectralEnd,
@ -143,10 +147,10 @@ var JpegImage = (function jpegImage() {
return n; return n;
return n + (-1 << length) + 1; return n + (-1 << length) + 1;
} }
function decodeBaseline(component, zz) { function decodeBaseline(component, offset) {
var t = decodeHuffman(component.huffmanTableDC); var t = decodeHuffman(component.huffmanTableDC);
var diff = t === 0 ? 0 : receiveAndExtend(t); var diff = t === 0 ? 0 : receiveAndExtend(t);
zz[0]= (component.pred += diff); component.blocks[offset] = (component.pred += diff);
var k = 1; var k = 1;
while (k < 64) { while (k < 64) {
var rs = decodeHuffman(component.huffmanTableAC); var rs = decodeHuffman(component.huffmanTableAC);
@ -159,20 +163,20 @@ var JpegImage = (function jpegImage() {
} }
k += r; k += r;
var z = dctZigZag[k]; var z = dctZigZag[k];
zz[z] = receiveAndExtend(s); component.blocks[offset + z] = receiveAndExtend(s);
k++; k++;
} }
} }
function decodeDCFirst(component, zz) { function decodeDCFirst(component, offset) {
var t = decodeHuffman(component.huffmanTableDC); var t = decodeHuffman(component.huffmanTableDC);
var diff = t === 0 ? 0 : (receiveAndExtend(t) << successive); var diff = t === 0 ? 0 : (receiveAndExtend(t) << successive);
zz[0] = (component.pred += diff); component.blocks[offset] = (component.pred += diff);
} }
function decodeDCSuccessive(component, zz) { function decodeDCSuccessive(component, offset) {
zz[0] |= readBit() << successive; component.blocks[offset] |= readBit() << successive;
} }
var eobrun = 0; var eobrun = 0;
function decodeACFirst(component, zz) { function decodeACFirst(component, offset) {
if (eobrun > 0) { if (eobrun > 0) {
eobrun--; eobrun--;
return; return;
@ -191,12 +195,12 @@ var JpegImage = (function jpegImage() {
} }
k += r; k += r;
var z = dctZigZag[k]; var z = dctZigZag[k];
zz[z] = receiveAndExtend(s) * (1 << successive); component.blocks[offset + z] = receiveAndExtend(s) * (1 << successive);
k++; k++;
} }
} }
var successiveACState = 0, successiveACNextValue; var successiveACState = 0, successiveACNextValue;
function decodeACSuccessive(component, zz) { function decodeACSuccessive(component, offset) {
var k = spectralStart, e = spectralEnd, r = 0; var k = spectralStart, e = spectralEnd, r = 0;
while (k <= e) { while (k <= e) {
var z = dctZigZag[k]; var z = dctZigZag[k];
@ -221,25 +225,26 @@ var JpegImage = (function jpegImage() {
continue; continue;
case 1: // skipping r zero items case 1: // skipping r zero items
case 2: case 2:
if (zz[z]) if (component.blocks[offset + z]) {
zz[z] += (readBit() << successive); component.blocks[offset + z] += (readBit() << successive);
else { } else {
r--; r--;
if (r === 0) if (r === 0)
successiveACState = successiveACState == 2 ? 3 : 0; successiveACState = successiveACState == 2 ? 3 : 0;
} }
break; break;
case 3: // set value for a zero item case 3: // set value for a zero item
if (zz[z]) if (component.blocks[offset + z]) {
zz[z] += (readBit() << successive); component.blocks[offset + z] += (readBit() << successive);
else { } else {
zz[z] = successiveACNextValue << successive; component.blocks[offset + z] = successiveACNextValue << successive;
successiveACState = 0; successiveACState = 0;
} }
break; break;
case 4: // eob case 4: // eob
if (zz[z]) if (component.blocks[offset + z]) {
zz[z] += (readBit() << successive); component.blocks[offset + z] += (readBit() << successive);
}
break; break;
} }
k++; k++;
@ -250,17 +255,20 @@ var JpegImage = (function jpegImage() {
successiveACState = 0; successiveACState = 0;
} }
} }
function decodeMcu(component, decode, mcu, row, col) { function decodeMcu(component, decode, mcu, row, col) {
var mcuRow = (mcu / mcusPerLine) | 0; var mcuRow = (mcu / mcusPerLine) | 0;
var mcuCol = mcu % mcusPerLine; var mcuCol = mcu % mcusPerLine;
var blockRow = mcuRow * component.v + row; var blockRow = mcuRow * component.v + row;
var blockCol = mcuCol * component.h + col; var blockCol = mcuCol * component.h + col;
decode(component, component.blocks[blockRow][blockCol]);
decode(component, getBlockBufferOffset(component, blockRow, blockCol));
} }
function decodeBlock(component, decode, mcu) { function decodeBlock(component, decode, mcu) {
var blockRow = (mcu / component.blocksPerLine) | 0; var blockRow = (mcu / component.blocksPerLine) | 0;
var blockCol = mcu % component.blocksPerLine; var blockCol = mcu % component.blocksPerLine;
decode(component, component.blocks[blockRow][blockCol]); decode(component, getBlockBufferOffset(component, blockRow, blockCol));
} }
var componentsLength = components.length; var componentsLength = components.length;
@ -330,184 +338,188 @@ var JpegImage = (function jpegImage() {
return offset - startOffset; return offset - startOffset;
} }
function buildComponentData(frame, component) { // A port of poppler's IDCT method which in turn is taken from:
var lines = []; // Christoph Loeffler, Adriaan Ligtenberg, George S. Moschytz,
var blocksPerLine = component.blocksPerLine; // "Practical Fast 1-D DCT Algorithms with 11 Multiplications",
var blocksPerColumn = component.blocksPerColumn; // IEEE Intl. Conf. on Acoustics, Speech & Signal Processing, 1989,
var samplesPerLine = blocksPerLine << 3; // 988-991.
var R = new Int32Array(64); function quantizeAndInverse(component, blockBufferOffset, p) {
var qt = component.quantizationTable;
// A port of poppler's IDCT method which in turn is taken from: var v0, v1, v2, v3, v4, v5, v6, v7, t;
// Christoph Loeffler, Adriaan Ligtenberg, George S. Moschytz, var i;
// "Practical Fast 1-D DCT Algorithms with 11 Multiplications",
// IEEE Intl. Conf. on Acoustics, Speech & Signal Processing, 1989, // dequant
// 988-991. for (i = 0; i < 64; i++)
function quantizeAndInverse(zz, p) { p[i] = component.blocks[blockBufferOffset + i] * qt[i];
var qt = component.quantizationTable;
var v0, v1, v2, v3, v4, v5, v6, v7, t; // inverse DCT on rows
var i; for (i = 0; i < 8; ++i) {
var row = 8 * i;
// dequant
for (i = 0; i < 64; i++) // check for all-zero AC coefficients
p[i] = zz[i] * qt[i]; if (p[1 + row] == 0 && p[2 + row] == 0 && p[3 + row] == 0 &&
p[4 + row] == 0 && p[5 + row] == 0 && p[6 + row] == 0 &&
// inverse DCT on rows p[7 + row] == 0) {
for (i = 0; i < 8; ++i) { t = (dctSqrt2 * p[0 + row] + 512) >> 10;
var row = 8 * i; p[0 + row] = t;
p[1 + row] = t;
// check for all-zero AC coefficients p[2 + row] = t;
if (p[1 + row] == 0 && p[2 + row] == 0 && p[3 + row] == 0 && p[3 + row] = t;
p[4 + row] == 0 && p[5 + row] == 0 && p[6 + row] == 0 && p[4 + row] = t;
p[7 + row] == 0) { p[5 + row] = t;
t = (dctSqrt2 * p[0 + row] + 512) >> 10; p[6 + row] = t;
p[0 + row] = t; p[7 + row] = t;
p[1 + row] = t; continue;
p[2 + row] = t;
p[3 + row] = t;
p[4 + row] = t;
p[5 + row] = t;
p[6 + row] = t;
p[7 + row] = t;
continue;
}
// stage 4
v0 = (dctSqrt2 * p[0 + row] + 128) >> 8;
v1 = (dctSqrt2 * p[4 + row] + 128) >> 8;
v2 = p[2 + row];
v3 = p[6 + row];
v4 = (dctSqrt1d2 * (p[1 + row] - p[7 + row]) + 128) >> 8;
v7 = (dctSqrt1d2 * (p[1 + row] + p[7 + row]) + 128) >> 8;
v5 = p[3 + row] << 4;
v6 = p[5 + row] << 4;
// stage 3
t = (v0 - v1+ 1) >> 1;
v0 = (v0 + v1 + 1) >> 1;
v1 = t;
t = (v2 * dctSin6 + v3 * dctCos6 + 128) >> 8;
v2 = (v2 * dctCos6 - v3 * dctSin6 + 128) >> 8;
v3 = t;
t = (v4 - v6 + 1) >> 1;
v4 = (v4 + v6 + 1) >> 1;
v6 = t;
t = (v7 + v5 + 1) >> 1;
v5 = (v7 - v5 + 1) >> 1;
v7 = t;
// stage 2
t = (v0 - v3 + 1) >> 1;
v0 = (v0 + v3 + 1) >> 1;
v3 = t;
t = (v1 - v2 + 1) >> 1;
v1 = (v1 + v2 + 1) >> 1;
v2 = t;
t = (v4 * dctSin3 + v7 * dctCos3 + 2048) >> 12;
v4 = (v4 * dctCos3 - v7 * dctSin3 + 2048) >> 12;
v7 = t;
t = (v5 * dctSin1 + v6 * dctCos1 + 2048) >> 12;
v5 = (v5 * dctCos1 - v6 * dctSin1 + 2048) >> 12;
v6 = t;
// stage 1
p[0 + row] = v0 + v7;
p[7 + row] = v0 - v7;
p[1 + row] = v1 + v6;
p[6 + row] = v1 - v6;
p[2 + row] = v2 + v5;
p[5 + row] = v2 - v5;
p[3 + row] = v3 + v4;
p[4 + row] = v3 - v4;
} }
// inverse DCT on columns // stage 4
for (i = 0; i < 8; ++i) { v0 = (dctSqrt2 * p[0 + row] + 128) >> 8;
var col = i; v1 = (dctSqrt2 * p[4 + row] + 128) >> 8;
v2 = p[2 + row];
// check for all-zero AC coefficients v3 = p[6 + row];
if (p[1*8 + col] == 0 && p[2*8 + col] == 0 && p[3*8 + col] == 0 && v4 = (dctSqrt1d2 * (p[1 + row] - p[7 + row]) + 128) >> 8;
p[4*8 + col] == 0 && p[5*8 + col] == 0 && p[6*8 + col] == 0 && v7 = (dctSqrt1d2 * (p[1 + row] + p[7 + row]) + 128) >> 8;
p[7*8 + col] == 0) { v5 = p[3 + row] << 4;
t = (dctSqrt2 * p[i+0] + 8192) >> 14; v6 = p[5 + row] << 4;
p[0*8 + col] = t;
p[1*8 + col] = t; // stage 3
p[2*8 + col] = t; t = (v0 - v1+ 1) >> 1;
p[3*8 + col] = t; v0 = (v0 + v1 + 1) >> 1;
p[4*8 + col] = t; v1 = t;
p[5*8 + col] = t; t = (v2 * dctSin6 + v3 * dctCos6 + 128) >> 8;
p[6*8 + col] = t; v2 = (v2 * dctCos6 - v3 * dctSin6 + 128) >> 8;
p[7*8 + col] = t; v3 = t;
continue; t = (v4 - v6 + 1) >> 1;
} v4 = (v4 + v6 + 1) >> 1;
v6 = t;
t = (v7 + v5 + 1) >> 1;
v5 = (v7 - v5 + 1) >> 1;
v7 = t;
// stage 2
t = (v0 - v3 + 1) >> 1;
v0 = (v0 + v3 + 1) >> 1;
v3 = t;
t = (v1 - v2 + 1) >> 1;
v1 = (v1 + v2 + 1) >> 1;
v2 = t;
t = (v4 * dctSin3 + v7 * dctCos3 + 2048) >> 12;
v4 = (v4 * dctCos3 - v7 * dctSin3 + 2048) >> 12;
v7 = t;
t = (v5 * dctSin1 + v6 * dctCos1 + 2048) >> 12;
v5 = (v5 * dctCos1 - v6 * dctSin1 + 2048) >> 12;
v6 = t;
// stage 1
p[0 + row] = v0 + v7;
p[7 + row] = v0 - v7;
p[1 + row] = v1 + v6;
p[6 + row] = v1 - v6;
p[2 + row] = v2 + v5;
p[5 + row] = v2 - v5;
p[3 + row] = v3 + v4;
p[4 + row] = v3 - v4;
}
// stage 4 // inverse DCT on columns
v0 = (dctSqrt2 * p[0*8 + col] + 2048) >> 12; for (i = 0; i < 8; ++i) {
v1 = (dctSqrt2 * p[4*8 + col] + 2048) >> 12; var col = i;
v2 = p[2*8 + col];
v3 = p[6*8 + col]; // check for all-zero AC coefficients
v4 = (dctSqrt1d2 * (p[1*8 + col] - p[7*8 + col]) + 2048) >> 12; if (p[1*8 + col] == 0 && p[2*8 + col] == 0 && p[3*8 + col] == 0 &&
v7 = (dctSqrt1d2 * (p[1*8 + col] + p[7*8 + col]) + 2048) >> 12; p[4*8 + col] == 0 && p[5*8 + col] == 0 && p[6*8 + col] == 0 &&
v5 = p[3*8 + col]; p[7*8 + col] == 0) {
v6 = p[5*8 + col]; t = (dctSqrt2 * p[i+0] + 8192) >> 14;
p[0*8 + col] = t;
// stage 3 p[1*8 + col] = t;
t = (v0 - v1 + 1) >> 1; p[2*8 + col] = t;
v0 = (v0 + v1 + 1) >> 1; p[3*8 + col] = t;
v1 = t; p[4*8 + col] = t;
t = (v2 * dctSin6 + v3 * dctCos6 + 2048) >> 12; p[5*8 + col] = t;
v2 = (v2 * dctCos6 - v3 * dctSin6 + 2048) >> 12; p[6*8 + col] = t;
v3 = t; p[7*8 + col] = t;
t = (v4 - v6 + 1) >> 1; continue;
v4 = (v4 + v6 + 1) >> 1;
v6 = t;
t = (v7 + v5 + 1) >> 1;
v5 = (v7 - v5 + 1) >> 1;
v7 = t;
// stage 2
t = (v0 - v3 + 1) >> 1;
v0 = (v0 + v3 + 1) >> 1;
v3 = t;
t = (v1 - v2 + 1) >> 1;
v1 = (v1 + v2 + 1) >> 1;
v2 = t;
t = (v4 * dctSin3 + v7 * dctCos3 + 2048) >> 12;
v4 = (v4 * dctCos3 - v7 * dctSin3 + 2048) >> 12;
v7 = t;
t = (v5 * dctSin1 + v6 * dctCos1 + 2048) >> 12;
v5 = (v5 * dctCos1 - v6 * dctSin1 + 2048) >> 12;
v6 = t;
// stage 1
p[0*8 + col] = v0 + v7;
p[7*8 + col] = v0 - v7;
p[1*8 + col] = v1 + v6;
p[6*8 + col] = v1 - v6;
p[2*8 + col] = v2 + v5;
p[5*8 + col] = v2 - v5;
p[3*8 + col] = v3 + v4;
p[4*8 + col] = v3 - v4;
} }
// convert to 8-bit integers // stage 4
for (i = 0; i < 64; ++i) { v0 = (dctSqrt2 * p[0*8 + col] + 2048) >> 12;
p[i] = clampTo8bit((p[i] + 2056) >> 4); v1 = (dctSqrt2 * p[4*8 + col] + 2048) >> 12;
} v2 = p[2*8 + col];
v3 = p[6*8 + col];
v4 = (dctSqrt1d2 * (p[1*8 + col] - p[7*8 + col]) + 2048) >> 12;
v7 = (dctSqrt1d2 * (p[1*8 + col] + p[7*8 + col]) + 2048) >> 12;
v5 = p[3*8 + col];
v6 = p[5*8 + col];
// stage 3
t = (v0 - v1 + 1) >> 1;
v0 = (v0 + v1 + 1) >> 1;
v1 = t;
t = (v2 * dctSin6 + v3 * dctCos6 + 2048) >> 12;
v2 = (v2 * dctCos6 - v3 * dctSin6 + 2048) >> 12;
v3 = t;
t = (v4 - v6 + 1) >> 1;
v4 = (v4 + v6 + 1) >> 1;
v6 = t;
t = (v7 + v5 + 1) >> 1;
v5 = (v7 - v5 + 1) >> 1;
v7 = t;
// stage 2
t = (v0 - v3 + 1) >> 1;
v0 = (v0 + v3 + 1) >> 1;
v3 = t;
t = (v1 - v2 + 1) >> 1;
v1 = (v1 + v2 + 1) >> 1;
v2 = t;
t = (v4 * dctSin3 + v7 * dctCos3 + 2048) >> 12;
v4 = (v4 * dctCos3 - v7 * dctSin3 + 2048) >> 12;
v7 = t;
t = (v5 * dctSin1 + v6 * dctCos1 + 2048) >> 12;
v5 = (v5 * dctCos1 - v6 * dctSin1 + 2048) >> 12;
v6 = t;
// stage 1
p[0*8 + col] = v0 + v7;
p[7*8 + col] = v0 - v7;
p[1*8 + col] = v1 + v6;
p[6*8 + col] = v1 - v6;
p[2*8 + col] = v2 + v5;
p[5*8 + col] = v2 - v5;
p[3*8 + col] = v3 + v4;
p[4*8 + col] = v3 - v4;
} }
// convert to 8-bit integers
for (i = 0; i < 64; ++i) {
p[i] = clampTo8bit((p[i] + 2056) >> 4);
}
}
function buildComponentData(frame, component) {
var lines = [];
var blocksPerLine = component.blocksPerLine;
var blocksPerColumn = component.blocksPerColumn;
var samplesPerLine = blocksPerLine << 3;
var R = new Int16Array(64);
var i, j; var i, j;
for (var blockRow = 0; blockRow < blocksPerColumn; blockRow++) { for (var blockRow = 0; blockRow < blocksPerColumn; blockRow++) {
var scanLine = blockRow << 3; var scanLine = blockRow << 3;
for (i = 0; i < 8; i++) for (i = 0; i < 8; i++) {
lines.push(new Uint8Array(samplesPerLine)); lines.push(new Uint8Array(samplesPerLine));
}
for (var blockCol = 0; blockCol < blocksPerLine; blockCol++) { for (var blockCol = 0; blockCol < blocksPerLine; blockCol++) {
quantizeAndInverse(component.blocks[blockRow][blockCol], R);
quantizeAndInverse(component,
getBlockBufferOffset(component, blockRow, blockCol),
R);
var offset = 0, sample = blockCol << 3; var offset = 0, sample = blockCol << 3;
for (j = 0; j < 8; j++) { for (j = 0; j < 8; j++) {
var line = lines[scanLine + j]; var line = lines[scanLine + j];
for (i = 0; i < 8; i++) for (i = 0; i < 8; i++) {
line[sample + i] = R[offset++]; line[sample + i] = R[offset++];
}
} }
} }
} }
@ -532,60 +544,50 @@ var JpegImage = (function jpegImage() {
}).bind(this); }).bind(this);
xhr.send(null); xhr.send(null);
}, },
parse: function parse(data) { parse: function parse(data) {
var offset = 0, length = data.length;
function readUint16() { function readUint16() {
var value = (data[offset] << 8) | data[offset + 1]; var value = (data[offset] << 8) | data[offset + 1];
offset += 2; offset += 2;
return value; return value;
} }
function readDataBlock() { function readDataBlock() {
var length = readUint16(); var length = readUint16();
var array = data.subarray(offset, offset + length - 2); var array = data.subarray(offset, offset + length - 2);
offset += array.length; offset += array.length;
return array; return array;
} }
function prepareComponents(frame) { function prepareComponents(frame) {
var maxH = 0, maxV = 0; var mcusPerLine = Math.ceil(frame.samplesPerLine / (frame.maxH << 3));
var component, componentId; var mcusPerColumn = Math.ceil(frame.scanLines / (frame.maxV << 3));
for (componentId in frame.components) { for (var i = 0; i < frame.components.length; i++) {
if (frame.components.hasOwnProperty(componentId)) { component = frame.components[i];
component = frame.components[componentId]; var blocksPerLine = Math.ceil(Math.ceil(frame.samplesPerLine / 8) * component.h / maxH);
if (maxH < component.h) maxH = component.h; var blocksPerColumn = Math.ceil(Math.ceil(frame.scanLines / 8) * component.v / maxV);
if (maxV < component.v) maxV = component.v; var blocksPerLineForMcu = mcusPerLine * component.h;
} var blocksPerColumnForMcu = mcusPerColumn * component.v;
}
var mcusPerLine = Math.ceil(frame.samplesPerLine / 8 / maxH); var blocksBufferSize = 64 * blocksPerColumnForMcu
var mcusPerColumn = Math.ceil(frame.scanLines / 8 / maxV); * blocksPerLineForMcu;
for (componentId in frame.components) { var blocks = new Int16Array(blocksBufferSize);
if (frame.components.hasOwnProperty(componentId)) {
component = frame.components[componentId]; component.blocksPerLine = blocksPerLine;
var blocksPerLine = Math.ceil(Math.ceil(frame.samplesPerLine / 8) * component.h / maxH); component.blocksPerColumn = blocksPerColumn;
var blocksPerColumn = Math.ceil(Math.ceil(frame.scanLines / 8) * component.v / maxV); component.blocks = blocks;
var blocksPerLineForMcu = mcusPerLine * component.h;
var blocksPerColumnForMcu = mcusPerColumn * component.v;
var blocks = [];
for (var i = 0; i < blocksPerColumnForMcu; i++) {
var row = [];
for (var j = 0; j < blocksPerLineForMcu; j++)
row.push(new Int16Array(64));
blocks.push(row);
}
component.blocksPerLine = blocksPerLine;
component.blocksPerColumn = blocksPerColumn;
component.blocks = blocks;
}
} }
frame.maxH = maxH;
frame.maxV = maxV;
frame.mcusPerLine = mcusPerLine; frame.mcusPerLine = mcusPerLine;
frame.mcusPerColumn = mcusPerColumn; frame.mcusPerColumn = mcusPerColumn;
} }
var offset = 0, length = data.length;
var jfif = null; var jfif = null;
var adobe = null; var adobe = null;
var pixels = null; var pixels = null;
var frame, resetInterval; var frame, resetInterval;
var quantizationTables = [], frames = []; var quantizationTables = [];
var huffmanTablesAC = [], huffmanTablesDC = []; var huffmanTablesAC = [], huffmanTablesDC = [];
var fileMarker = readUint16(); var fileMarker = readUint16();
if (fileMarker != 0xFFD8) { // SOI (Start of Image) if (fileMarker != 0xFFD8) { // SOI (Start of Image)
@ -668,6 +670,9 @@ var JpegImage = (function jpegImage() {
case 0xFFC0: // SOF0 (Start of Frame, Baseline DCT) case 0xFFC0: // SOF0 (Start of Frame, Baseline DCT)
case 0xFFC1: // SOF1 (Start of Frame, Extended DCT) case 0xFFC1: // SOF1 (Start of Frame, Extended DCT)
case 0xFFC2: // SOF2 (Start of Frame, Progressive DCT) case 0xFFC2: // SOF2 (Start of Frame, Progressive DCT)
if (frame) {
throw "Only single frame JPEGs supported";
}
readUint16(); // skip data length readUint16(); // skip data length
frame = {}; frame = {};
frame.extended = (fileMarker === 0xFFC1); frame.extended = (fileMarker === 0xFFC1);
@ -675,25 +680,28 @@ var JpegImage = (function jpegImage() {
frame.precision = data[offset++]; frame.precision = data[offset++];
frame.scanLines = readUint16(); frame.scanLines = readUint16();
frame.samplesPerLine = readUint16(); frame.samplesPerLine = readUint16();
frame.components = {}; frame.components = [];
frame.componentsOrder = []; frame.componentIds = {};
var componentsCount = data[offset++], componentId; var componentsCount = data[offset++], componentId;
var maxH = 0, maxV = 0; var maxH = 0, maxV = 0;
for (i = 0; i < componentsCount; i++) { for (i = 0; i < componentsCount; i++) {
componentId = data[offset]; componentId = data[offset];
var h = data[offset + 1] >> 4; var h = data[offset + 1] >> 4;
var v = data[offset + 1] & 15; var v = data[offset + 1] & 15;
if (maxH < h) maxH = h;
if (maxV < v) maxV = v;
var qId = data[offset + 2]; var qId = data[offset + 2];
frame.componentsOrder.push(componentId); var l = frame.components.push({
frame.components[componentId] = {
h: h, h: h,
v: v, v: v,
quantizationTable: quantizationTables[qId] quantizationTable: quantizationTables[qId]
}; });
frame.componentIds[componentId] = l - 1;
offset += 3; offset += 3;
} }
frame.maxH = maxH;
frame.maxV = maxV;
prepareComponents(frame); prepareComponents(frame);
frames.push(frame);
break; break;
case 0xFFC4: // DHT (Define Huffman Tables) case 0xFFC4: // DHT (Define Huffman Tables)
@ -725,7 +733,8 @@ var JpegImage = (function jpegImage() {
var selectorsCount = data[offset++]; var selectorsCount = data[offset++];
var components = [], component; var components = [], component;
for (i = 0; i < selectorsCount; i++) { for (i = 0; i < selectorsCount; i++) {
component = frame.components[data[offset++]]; var componentIndex = frame.componentIds[data[offset++]];
component = frame.components[componentIndex];
var tableSpec = data[offset++]; var tableSpec = data[offset++];
component.huffmanTableDC = huffmanTablesDC[tableSpec >> 4]; component.huffmanTableDC = huffmanTablesDC[tableSpec >> 4];
component.huffmanTableAC = huffmanTablesAC[tableSpec & 15]; component.huffmanTableAC = huffmanTablesAC[tableSpec & 15];
@ -752,16 +761,14 @@ var JpegImage = (function jpegImage() {
} }
fileMarker = readUint16(); fileMarker = readUint16();
} }
if (frames.length != 1)
throw "only single frame JPEGs supported";
this.width = frame.samplesPerLine; this.width = frame.samplesPerLine;
this.height = frame.scanLines; this.height = frame.scanLines;
this.jfif = jfif; this.jfif = jfif;
this.adobe = adobe; this.adobe = adobe;
this.components = []; this.components = [];
for (var i = 0; i < frame.componentsOrder.length; i++) { for (var i = 0; i < frame.components.length; i++) {
var component = frame.components[frame.componentsOrder[i]]; var component = frame.components[i];
this.components.push({ this.components.push({
lines: buildComponentData(frame, component), lines: buildComponentData(frame, component),
scaleX: component.h / frame.maxH, scaleX: component.h / frame.maxH,

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