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<html>
<head>
<script src="jpg.js"></script>
<script src="DataStream.js"></script>
</head>
<body>
<h1>JPEG marker reader</h1>
<h3>Select a JPEG or TIFF file</h3>
<input type="file"><br>
<pre></pre>
<script>
document.querySelector('input[type="file"]').onchange = function(e) {
var reader = new FileReader();
var tiffByteSize = {
1:1, 2:1, 3:2, 4:4, 5:8, 6:1, 7:1, 8:2, 9:4, 10:8, 11:4, 12:8
};
var tiffTag = [
'tag', 'uint16',
'type', 'uint16',
'count', 'uint32',
'value', function(ds, s) {
var p = ds.position;
if (s.count * tiffByteSize[s.type] > 4) {
ds.seek(ds.readUint32());
}
var v = {error: 'Unknown TIFF Field'};
switch (s.type) {
case 1: v = ds.readUint8Array(s.count); break;
case 2: v = ds.readString(s.count); break;
case 3: v = ds.readUint16Array(s.count); break;
case 4: v = ds.readUint32Array(s.count); break;
case 5: v = ds.readUint32Array(2*s.count); break;
case 6: v = ds.readInt8Array(s.count); break;
case 7: v = ds.readInt8Array(s.count); break;
case 8: v = ds.readInt16Array(s.count); break;
case 9: v = ds.readInt32Array(s.count); break;
case 10: v = ds.readInt32Array(2*s.count); break;
case 11: v = ds.readFloat32(s.count); break;
case 12: v = ds.readFloat64(s.count); break;
}
ds.position = p + 4;
if (v.length && s.type != 2) {
v = Array.prototype.join.call(v);
}
return v;
}
];
var parseTIFF = function(u8) {
var rv = {};
var ds = new DataStream(u8);
rv.endianness = ds.readString(2);
ds.endianness = rv.endianness == 'MM' ? DataStream.BIG_ENDIAN : DataStream.LITTLE_ENDIAN;
rv.magic = ds.readUint16();
if (rv.magic != 42) return null;
rv.firstOff = ds.readUint32();
ds.seek(rv.firstOff);
var h = [];
rv.entries = h;
rv.dirOffsets = [];
while (true) {
numEntries = ds.readUint16();
for (var i = 0; i<numEntries; i++) {
h.push(ds.readStruct(tiffTag));
}
nextOff = ds.readUint32();
if (nextOff) {
ds.seek(nextOff);
rv.dirOffsets.push(nextOff);
} else {
break;
}
}
return rv;
};
var jpegMarkers = {
// Huffman coding SOFs
0xFFC0: "SOF0", // baseline DCT
0xFFC1: "SOF1", // extended sequential DCT
0xFFC2: "SOF2", // progressive DCT
0xFFC3: "SOF3", // lossless (sequential)
0xFFC5: "SOF5", // differential sequential DCT
0xFFC6: "SOF6", // differential progressive DCT
0xFFC7: "SOF7", // differential lossless (sequential)
// Arithmetic coding SOFs
0xFFC8: "JPG", // reserved
0xFFC9: "SOF9", // extended sequential DCT
0xFFCA: "SOF10", // progressive DCT
0xFFCB: "SOF11", // lossless sequential
0xFFCD: "SOF13", // differential sequential DCT
0xFFCE: "SOF14", // differential progressive DCT
0xFFCF: "SOF15", // differential lossless DCT
0xFFC4: "DHT", // Define Huffman table(s)
0xFFCC: "DAC", // Define arithmetic coding conditioning(s)
// Restart interval termination
0xFFD0: "RST0",
0xFFD1: "RST1",
0xFFD2: "RST2",
0xFFD3: "RST3",
0xFFD4: "RST4",
0xFFD5: "RST5",
0xFFD6: "RST6",
0xFFD7: "RST7",
// other markers
0xFFD8: "SOI", // start of image
0xFFD9: "EOI", // end of image
0xFFDA: "SOS", // start of scan
0xFFDB: "DQT", // define quantization table(s)
0xFFDC: "DNL", // define number of lines
0xFFDD: "DRI", // define restart interval
0xFFDE: "DHP", // define hierarchical progression
0xFFDF: "EXP", // expand reference component(s)
// APP markers
0xFFE0: "APP0",
0xFFE1: "APP1",
0xFFE2: "APP2",
0xFFE3: "APP3",
0xFFE4: "APP4",
0xFFE5: "APP5",
0xFFE6: "APP6",
0xFFE7: "APP7",
0xFFE8: "APP8",
0xFFE9: "APP9",
0xFFEA: "APP10",
0xFFEB: "APP11",
0xFFEC: "APP12",
0xFFED: "APP13",
0xFFEE: "APP14",
0xFFEF: "APP15",
// JPEG extensions
0xFFF0: "JPG0",
0xFFF1: "JPG1",
0xFFF2: "JPG2",
0xFFF3: "JPG3",
0xFFF4: "JPG4",
0xFFF5: "JPG5",
0xFFF6: "JPG6",
0xFFF7: "JPG7",
0xFFF8: "JPG8",
0xFFF9: "JPG9",
0xFFFA: "JPG10",
0xFFFB: "JPG11",
0xFFFC: "JPG12",
0xFFFD: "JPG13",
0xFFFE: "COM", // comment
0xFF01: "TEM*" // For temporary private use in arithmetic coding
};
var jpegStruct = [
'start', function(ds){ var t = ds.readUint16(); return t == 0xFFD8 ? t : null; },
'markers', ['[]', [
'tag', function(ds){ var t = ds.readUint16(); return t == 0xFFD9 ? null : t; },
'tagName', function(ds, s) { return jpegMarkers[s.tag] || "Unknown"; },
'length', 'uint16be',
'data', {
get: function(ds, s) {
switch (s.tag) {
case 0xFFE1: // EXIF
var exif = ds.readString(6);
if (exif == 'Exif\000\000') {
// parse rest of Exif
return { exif: exif, data: parseTIFF(ds.mapUint8Array(s.length - 8)) };
} else {
ds.position -= exif.length;
var xmp = ds.readCString();
if (xmp == "http://ns.adobe.com/xap/1.0/") {
return { xmp: xmp, data: ds.readString(s.length-2-xmp.length-1) };
} else {
ds.position -= xmp.length+1;
return ds.mapUint8Array(s.length - 2).length;
}
}
break;
case 0xFFE0: // APP0
if (s.length >= 7) { // probably a JFIF
var p = ds.position;
var jfif = ds.readCString(5);
if (jfif == 'JFIF' || jfif == 'JFXX') {
var jfifStruct = [
'majorVersion', 'uint8',
'minorVersion', 'uint8',
'units', 'uint8',
'xDensity', 'uint16',
'yDensity', 'uint16',
'thumbnail', [
'width', 'uint8',
'height', 'uint8',
'data', ['[]', 'uint8', '*']]];
if (jfif == 'JFXX') {
jfifStruct.unshift('extensionCode', 'uint8');
}
var u8 = ds.mapUint8Array(s.length-7);
var rv = new DataStream(u8, null, DataStream.BIG_ENDIAN).readStruct(jfifStruct);
if (!rv) {
ds.position = p;
return ds.readString(s.length-2);
}
return {jfif: jfif, data: rv};
} else {
ds.position -= 5;
return ds.readString(s.length-2);
}
} else {
return ds.mapUint8Array(s.length - 2).length;
}
break;
case 0xFFE2: // APP2, ICC Profile most likely
return ds.readString(s.length-2);
case 0xFFED: // APP13, IPTC / Photoshop IRB
return ds.readString(s.length-2);
case 0xFFDD: // DRI
return s.length == 4 ? ds.readUint16() : ds.mapUint8Array(s.length-2).length;
case 0xFFDA: // image stream
var p = ds.position;
var cmpCount = ds.readUint8();
var cs = [];
for (var i=0; i<cmpCount; i++) {
cs.push({id: ds.readUint8(), huffmanTable: ds.readUint8()});
}
ds.position = p + s.length;
p = ds.position;
var u8 = ds.mapUint8Array(ds.byteLength-ds.position);
for (var i=1; i<u8.length; i++) {
if (u8[i-1] == 0xFF && u8[i] == 0xD9) {
break;
}
}
ds.position = p;
return {components: cs, imageData: ds.mapUint8Array(i-1).length};
break;
default:
return ds.mapUint8Array(s.length - 2).length;
break;
}
}
}
], '*'],
'end', function(ds){ var t = ds.readUint16(); return t == 0xFFD9 ? t : null; }
];
reader.onload = function(e) {
var ds = new DataStream(this.result);
ds.endianness = DataStream.BIG_ENDIAN;
var obj = ds.readStruct(jpegStruct) || parseTIFF(this.result);
pre = document.querySelector('pre');
if (obj) {
pre.textContent = JSON.stringify(obj, null, 4);
if (obj.start) {
var j = new JpegImage();
j.parse(new Uint8Array(this.result));
var c = document.createElement('canvas');
c.width = j.width; c.height = j.height;
var ctx = c.getContext('2d');
var id = ctx.getImageData(0,0,j.width, j.height);
j.copyToImageData(id);
ctx.putImageData(id, 0,0);
c.style.display = 'block';
pre.appendChild(c);
}
} else {
pre.textContent = "Failed to parse JPEG at "+ds.failurePosition+" :(";
}
};
reader.readAsArrayBuffer(this.files[0]);
};
</script>
</body>
</html>