kig/jsdecode.html

## jsdecode.html
<html>
<body>
<script>

var QRDecoder = function(imageData) {
	this.imageData = imageData;
	this.imageBits = new Int8Array(QRDecoder.MAX_SIZE * QRDecoder.MAX_SIZE);
	this.decodedBits = new Uint8Array( (QRDecoder.MAX_SIZE * QRDecoder.MAX_SIZE) >> 3 );
	this.size = -1;
	this.ecc = -1;
	this.mask = -1;
};

QRDecoder.MIN_SIZE = 21;
QRDecoder.MAX_SIZE = 177;

QRDecoder.prototype.setSize = function(size) {
	this.size = size;
	this.alignmentCoords = [];
	if (size > QRDecoder.MIN_SIZE) {
		var version = (size - QRDecoder.MIN_SIZE) / 4 + 1;
		this.version = version;
		var divs = 2 + (version / 7) | 0;
		var total_dist = size - 7 - 6;
		var divisor = 2 * (divs - 1);

		var step = ((((total_dist + (divisor / 2) | 0) + 1) / divisor) | 0) * 2;
		this.alignmentCoords.push(6);

		for (var i=divs-2; i >= 0; i--) {
			this.alignmentCoords.push(size - 7 - i * step)
		}
	}
};

QRDecoder.prototype.maskAlignmentPatterns = function() {
	var size = this.size;
	for (var i=0; i<this.alignmentCoords.length; i++) {
		for (var j=0; j<this.alignmentCoords.length; j++) {
			var x = this.alignmentCoords[i];
			var y = this.alignmentCoords[j];
			if (
				(x < 9 && y < 9) || // Skip top-left marker
				(x < 9 && y > this.size-9) || // Skip bottom-left marker
				(x > this.size-8 && y < 9)  // Skip top-right marker
			) {
				// skip
			} else {
				for (var py=-2; py<3; py++) {
					for (var px=-2; px<3; px++) {
						this.negateBit(x+px, y+py);
					}
				}
			}
		}
	}
	for (var y=0; y<9; y++) {
		for (var x=0; x<9; x++) {
			this.negateBit(x, y);
		}
	}
	for (var y=0; y<9; y++) {
		for (var x=size-8; x<size; x++) {
			this.negateBit(x, y);
		}
	}
	for (var y=size-8; y<size; y++) {
		for (var x=0; x<9; x++) {
			this.negateBit(x, y);
		}
	}
	for (var x=0; x<size; x++) {
		this.negateBit(x, 6);
	}
	for (var y=0; y<size; y++) {
		this.negateBit(6, y);
	}
	if (this.version >= 7) {
		for (var y=0; y<3; y++) {
			for (var x=0; x<7; x++) {
				this.negateBit(x, y+size-11);
			}
		}
		for (var y=0; y<7; y++) {
			for (var x=0; x<3; x++) {
				this.negateBit(x+size-11, y);
			}
		}
	}
};

QRDecoder.prototype.negateBit = function(x,y) {
	if (this.imageBits[y*this.size + x] < 0) return;
	this.imageBits[y*this.size + x] *= -1;
	this.imageBits[y*this.size + x] += -1;
};

QRDecoder.prototype.getBit = function(x,y){
	return this.imageBits[y*this.size + x];
};

QRDecoder.prototype.setBit = function(x,y,v){
	this.imageBits[y*this.size + x] = v;
};

QRDecoder.prototype.getMaskBit = function(x,y) {
	switch (this.mask) {
		case 0: return ((x+y)%2)^1;
		case 1: return (y%2)^1;
		case 2: return (x%3) === 0 ? 1 : 0;
		case 3: return ((x+y)%3 === 0) ? 1 : 0;
		case 4: return (((y/2 | 0) + (x/3 | 0)) % 2)^1;
		case 5: return ((y*x)%2 + (y*x)%3) === 0 ? 1 : 0;
		case 6: return (((y*x)%2 + (y*x)%3) % 2) ^ 1;
		case 7: return (((y+x)%2 + (y*x)%3) % 2) ^ 1;
		default:
			return 0;
	}
};

QRDecoder.prototype.getMaskedBit = function(x,y) {
	var mb = this.getMaskBit(x,y);
	var bb = this.imageBits[y*this.size + x];
	var b = bb^mb;
	// if (this.ctx) {
	// 	if (mb) {
	// 		this.ctx.fillStyle = 'rgba('+ (this.readIdx%256) +',0,'+ (255-this.readIdx%256) + ',1)';
	// 	} else {
	// 		this.ctx.fillStyle = 'rgba('+ (this.readIdx%256) +','+ (255-this.readIdx%256) + ', 255,1)';
	// 	}
	// 	this.readIdx++;
	// 	this.ctx.fillRect(x*4, y*4, 4, 4);
	// }
	return b;
};

QRDecoder.prototype.getFormat = function() {
	var ecc = ((this.getBit(0, 8)^1) << 1) + this.getBit(1, 8);
	var mask =
		((this.getBit(2, 8)^1) << 2) +
		(this.getBit(3, 8) << 1) +
		(this.getBit(4, 8)^1);

	this.ecc = ecc;
	this.mask = mask;

};


QRDecoder.prototype.notOnAlignmentMarker = function(x, y) {
	return this.getBit(x,y) !== -1;
}

QRDecoder.prototype.readDecodedBits = function() {
	this.readIdx = 0;
	var readBits = this.decodedBits;
	for (var i=0; i<readBits.length; i++) {
		readBits[i] = 0;
	}
	var x = this.size - 1;
	var y = this.size - 1;
	var dir = -1;
	var off = 0;
	var boff = 0;
	var bit = -1;
	this.firstEncoding = (
		(this.getMaskedBit(x,y) << 3) +
		(this.getMaskedBit(x-1,y) << 2) +
		(this.getMaskedBit(x,y-1) << 1) +
		(this.getMaskedBit(x-1,y-1))
	);
	y -= 2;
	while (x > 0) {
		if (y === 6) { // Skip horizontal timing sequence
			y += dir;
		}

		bit = this.getMaskedBit(x, y);
		if (bit >= 0) {
			boff = off >> 3;
			readBits[boff] += bit << (7 - (off-boff*8));
			off++;
		}

		bit = this.getMaskedBit(x-1, y);
		if (bit >= 0) {
			boff = off >> 3;
			readBits[boff] += bit << (7 - (off-boff*8));
			off++;
		}

		y += dir;

		if (y < 0 || y >= this.size) { // Reverse reading direction at top and bottom of marker
			dir *= -1;
			y += dir;
			x -= 2;
			if (x === 6) { // Skip vertical timing sequence
				x--;
			}
		}
	}
	this.bitLength = off;
	this.bitOffset = 0;
};

QRDecoder.prototype.readBits = function(n) {
	if (n === 8 && (this.bitOffset & 7) === 0) {
		var b = this.decodedBits[this.bitOffset >> 3];
		this.bitOffset += 8;
		return b;
	}
	var b = 0;
	var boff = 0;
	for (var i=0; i<n; i++) {
		b <<= 1;
		boff = this.bitOffset >> 3;
		b += (this.decodedBits[boff] >> (7-(this.bitOffset-boff*8))) & 1;
		this.bitOffset++;
	}
	return b;
};

QRDecoder.prototype.decodeNumeric = function() {
	var lengthBits = 10;
	if (this.version >= 27) {
		lengthBits = 14;
	} else if (this.version >= 10) {
		lengthBits = 12;
	}
	var length = this.readBits(lengthBits);
	var message = '';
	for (var i=0; i<length/3; i++) {
		var num = this.readBits(10);
		if (num < 10) {
			message += '00'+num.toString();
		} else if (num < 100) {
			message += '0'+num.toString();
		} else {
			message += num.toString();
		}
	}
	return {
		encoding: 1,
		length: length,
		message: message
	};
};

QRDecoder.ALPHANUMERIC_TABLE = [
'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F',
'G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V',
'W','X','Y','Z',' ','$','%','*','+','-','.','/',':'
];

QRDecoder.prototype.decodeAlphanumeric = function() {
	var lengthBits = 9;
	if (this.version >= 27) {
		lengthBits = 13;
	} else if (this.version >= 10) {
		lengthBits = 11;
	}
	var length = this.readBits(lengthBits);
	var message = '';
	for (var i=0; i<length; i+=2) {
		if (i === length-1) {
			var c1 = this.readBits(6);
			message += QRDecoder.ALPHANUMERIC_TABLE[c1];
		} else {
			var chars = this.readBits(11);
			var c1 = (chars / 45) | 0;
			message += QRDecoder.ALPHANUMERIC_TABLE[c1];
			var c2 = chars % 45;
			message += QRDecoder.ALPHANUMERIC_TABLE[c2];
		}
	}
	return {
		encoding: 2,
		length: length,
		message: message
	};
};

QRDecoder.prototype.decodeKanji = function() {
	var lengthBits = 8;
	if (this.version >= 27) {
		lengthBits = 12;
	} else if (this.version >= 10) {
		lengthBits = 10;
	}
	var length = this.readBits(lengthBits);
	return null;
};

QRDecoder.prototype.decodeByte = function() {
	var lengthBits = 8;
	if (this.version >= 27) {
		lengthBits = 16;
	} else if (this.version >= 10) {
		lengthBits = 16;
	}
	var length = this.readBits(lengthBits);
	var message = '';
	for (var i=0; i<length; i++) {
		message += String.fromCharCode(this.readBits(8));
	}
	return {
		encoding: 4,
		length: length,
		message: message
	};
};


QRDecoder.prototype.parseBits = function(bits) {
	var packets = [];
	var encoding = this.firstEncoding;
	while (this.bitOffset < this.bitLength) {
		// var raw = [];
		// for (var i=0; i<26; i++) {
		// 	var s = this.decodedBits[i].toString(16);
		// 	if (s.length < 2) s = '0' + s;
		// 	raw.push(s);
		// }
		// console.log(raw.join(" "));
		if (this.bitOffset > 0) {
			encoding = this.readBits(4);
		}
		if (encoding !== 0) {
			var packet;
			switch (encoding) {
				case 1: // Numeric
					packet = this.decodeNumeric();
					break;
				case 2: // Alphanumeric
					packet = this.decodeAlphanumeric();
					break;
				case 4: // Byte
					packet = this.decodeByte();
					break;
				case 8: // Kanji
					packet = this.decodeKanji();
					break;
				case 7: // ECI
					break;
			}
			if (packet) {
				packets.push(packet);
				return packets;
			}
		}
	}
	return packets;
};

QRDecoder.prototype.decode = function() {
	if (this.extractQRBits(this.imageData, this)) {
		this.getFormat();
		this.maskAlignmentPatterns();
		this.readDecodedBits();
		return this.parseBits();
	}
	return null;
};

QRDecoder.prototype.extractQRBits = function(imageData, bits) {
	var width = imageData.width;
	var height = imageData.height;
	var data = imageData.data;

	var bitMatrix = [];
	for (var y=0; y<height; y++) {
		var bit = 0;
		var rowBits = [];
		bitMatrix.push(rowBits);
		for (var x=0; x<width; x++) {
			var b = data[(y*width + x)*4] < 127 ? 1 : 0;
			if (b !== bit) {
				bit = b;
				rowBits.push(x, b&1);
			}
		}
	}
	while (bitMatrix.length && bitMatrix[0].length === 0) {
		bitMatrix.shift();
	}
	while (bitMatrix.length && bitMatrix[bitMatrix.length-1].length === 0) {
		bitMatrix.pop();
	}
	var rowMatch = function(a, b) {
		if (a === null || a.length !== b.length) {
			return false;
		}
		for (var i=0; i<a.length; i+=2) {
			if (Math.abs( a[i] - b[i] ) > 2) {
				return false;
			}
			if (a[i+1] !== b[i+1]) {
				return false;
			}
		}
		return true;
	};
	var bitRows = [];
	var lastBitRow = null;
	var lastRow = null;
	for (var i=0; i<bitMatrix.length; i++) {
		if (!rowMatch(lastRow, bitMatrix[i])) {
			var row = {length: 0, row: bitMatrix[i]};
			bitRows.push(row);
			lastBitRow = row;
		}
		lastBitRow.length++;
		lastRow = bitMatrix[i];
	}
	var bitRowLengths = [];
	for (var i=0; i<bitRows.length; i++) {
		var l = bitRows[i].length;
		bitRowLengths[l] = (bitRowLengths[l] || 0) + 1;
	}
	var maxCount = 0;
	var maxCountLength = 0;
	for (var i=2; i<bitRowLengths.length; i++) {
		if (bitRowLengths[i] && bitRowLengths[i] > maxCount) {
			maxCountLength = i;
			maxCount = bitRowLengths[i];
		}
	}
	bitRows = bitRows.filter(function(br) {
		return br.length > 1 && Math.abs(br.length - maxCountLength) <= 2;
	});

	var r = bitRows[0].row;
	var w = r[r.length-2] - r[0];
	var stride = w / bitRows.length;
	var off = r[0] + stride/2;

	var sz = bitRows.length;

	if (sz < QRDecoder.MIN_SIZE || sz > QRDecoder.MAX_SIZE || (sz - QRDecoder.MIN_SIZE) % 4 !== 0) {
		return false;
	}

	bits.setSize(sz);

	for (var y=0; y<bitRows.length; y++) {
		var r = bitRows[y].row;
		for (var x=0; x<bitRows.length; x++) {
			var xc = x * stride + off;
			var bit = 0;
			for (var j=r.length-2; j>=0; j-=2) {
				if (r[j] < xc) {
					bit = r[j+1];
					break;
				}
			}
			bits.setBit(x, y, bit);
		}
	}

	return bits;
};

</script>

<script>
	var img = new Image;
	img.src = 'qr.png';
	img.onload = function() {

		var width = Math.floor(this.width),
			height = Math.floor(this.height);

		var canvas = document.createElement('canvas');
		canvas.width = width*3;
		canvas.height = height*2;
		var ctx = canvas.getContext('2d');
		ctx.drawImage(this, 0, 0, width, height);
		var imageData = ctx.getImageData(0, 0, width, height);
		document.body.appendChild(canvas);

		var decoder = new QRDecoder(imageData);

		var tick = function() {
			console.time('qr processing x100');
			var msg = decoder.decode();
			for (var i=0; i<99; i++) {
				decoder.imageData = imageData;
				if (msg[0].message !== decoder.decode()[0].message) {
					throw "Non-stable decoding";
				}
			}
			console.timeEnd('qr processing x100');
			requestAnimationFrame(tick);
		};

		decoder.extractQRBits(imageData, decoder);
		decoder.getFormat();
		console.log("ecc: %d, mask: %d\n", decoder.ecc, decoder.mask);
		decoder.maskAlignmentPatterns();
		ctx.save();
		ctx.translate(width,26);
		for (var y=0; y<decoder.size; y++) {
			for (var x=0; x<decoder.size; x++) {
				var b = decoder.getBit(x,y);
				if (b) {
					ctx.fillStyle = b < 0 ? (b < -1 ? '#ff0000' : '#00ff00') : '#000000';
					ctx.fillRect( x*5 , y*5, 5, 5);
				}
			}
		}
		for (var i=0; i<10; i++) {
			decoder.decode();
		}
		// decoder.ctx = ctx;
		//ctx.restore();
		console.time('decode');
		var res = decoder.decode();
		console.timeEnd('decode');
		console.log(res);
		ctx.font = '18px sans-serif';
		ctx.fillText(res[0].message, 0, decoder.size * 5 + 20);
		// tick();
	};
</script>
</body>
</html>
	<html>
	<body>
	<script>

	var QRDecoder = function(imageData) {
	this.imageData = imageData;
	this.imageBits = new Int8Array(QRDecoder.MAX_SIZE * QRDecoder.MAX_SIZE);
	this.decodedBits = new Uint8Array( (QRDecoder.MAX_SIZE * QRDecoder.MAX_SIZE) >> 3 );
	this.size = -1;
	this.ecc = -1;
	this.mask = -1;
	};

	QRDecoder.MIN_SIZE = 21;
	QRDecoder.MAX_SIZE = 177;

	QRDecoder.prototype.setSize = function(size) {
	this.size = size;
	this.alignmentCoords = [];
	if (size > QRDecoder.MIN_SIZE) {
	var version = (size - QRDecoder.MIN_SIZE) / 4 + 1;
	this.version = version;
	var divs = 2 + (version / 7) \| 0;
	var total_dist = size - 7 - 6;
	var divisor = 2 * (divs - 1);

	var step = ((((total_dist + (divisor / 2) \| 0) + 1) / divisor) \| 0) * 2;
	this.alignmentCoords.push(6);

	for (var i=divs-2; i >= 0; i--) {
	this.alignmentCoords.push(size - 7 - i * step)
	}
	}
	};

	QRDecoder.prototype.maskAlignmentPatterns = function() {
	var size = this.size;
	for (var i=0; i<this.alignmentCoords.length; i++) {
	for (var j=0; j<this.alignmentCoords.length; j++) {
	var x = this.alignmentCoords[i];
	var y = this.alignmentCoords[j];
	if (
	(x < 9 && y < 9) \|\| // Skip top-left marker
	(x < 9 && y > this.size-9) \|\| // Skip bottom-left marker
	(x > this.size-8 && y < 9) // Skip top-right marker
	) {
	// skip
	} else {
	for (var py=-2; py<3; py++) {
	for (var px=-2; px<3; px++) {
	this.negateBit(x+px, y+py);
	}
	}
	}
	}
	}
	for (var y=0; y<9; y++) {
	for (var x=0; x<9; x++) {
	this.negateBit(x, y);
	}
	}
	for (var y=0; y<9; y++) {
	for (var x=size-8; x<size; x++) {
	this.negateBit(x, y);
	}
	}
	for (var y=size-8; y<size; y++) {
	for (var x=0; x<9; x++) {
	this.negateBit(x, y);
	}
	}
	for (var x=0; x<size; x++) {
	this.negateBit(x, 6);
	}
	for (var y=0; y<size; y++) {
	this.negateBit(6, y);
	}
	if (this.version >= 7) {
	for (var y=0; y<3; y++) {
	for (var x=0; x<7; x++) {
	this.negateBit(x, y+size-11);
	}
	}
	for (var y=0; y<7; y++) {
	for (var x=0; x<3; x++) {
	this.negateBit(x+size-11, y);
	}
	}
	}
	};

	QRDecoder.prototype.negateBit = function(x,y) {
	if (this.imageBits[y*this.size + x] < 0) return;
	this.imageBits[ythis.size + x] = -1;
	this.imageBits[y*this.size + x] += -1;
	};

	QRDecoder.prototype.getBit = function(x,y){
	return this.imageBits[y*this.size + x];
	};

	QRDecoder.prototype.setBit = function(x,y,v){
	this.imageBits[y*this.size + x] = v;
	};

	QRDecoder.prototype.getMaskBit = function(x,y) {
	switch (this.mask) {
	case 0: return ((x+y)%2)^1;
	case 1: return (y%2)^1;
	case 2: return (x%3) === 0 ? 1 : 0;
	case 3: return ((x+y)%3 === 0) ? 1 : 0;
	case 4: return (((y/2 \| 0) + (x/3 \| 0)) % 2)^1;
	case 5: return ((yx)%2 + (yx)%3) === 0 ? 1 : 0;
	case 6: return (((yx)%2 + (yx)%3) % 2) ^ 1;
	case 7: return (((y+x)%2 + (y*x)%3) % 2) ^ 1;
	default:
	return 0;
	}
	};

	QRDecoder.prototype.getMaskedBit = function(x,y) {
	var mb = this.getMaskBit(x,y);
	var bb = this.imageBits[y*this.size + x];
	var b = bb^mb;
	// if (this.ctx) {
	// if (mb) {
	// this.ctx.fillStyle = 'rgba('+ (this.readIdx%256) +',0,'+ (255-this.readIdx%256) + ',1)';
	// } else {
	// this.ctx.fillStyle = 'rgba('+ (this.readIdx%256) +','+ (255-this.readIdx%256) + ', 255,1)';
	// }
	// this.readIdx++;
	// this.ctx.fillRect(x4, y4, 4, 4);
	// }
	return b;
	};

	QRDecoder.prototype.getFormat = function() {
	var ecc = ((this.getBit(0, 8)^1) << 1) + this.getBit(1, 8);
	var mask =
	((this.getBit(2, 8)^1) << 2) +
	(this.getBit(3, 8) << 1) +
	(this.getBit(4, 8)^1);

	this.ecc = ecc;
	this.mask = mask;

	};


	QRDecoder.prototype.notOnAlignmentMarker = function(x, y) {
	return this.getBit(x,y) !== -1;
	}

	QRDecoder.prototype.readDecodedBits = function() {
	this.readIdx = 0;
	var readBits = this.decodedBits;
	for (var i=0; i<readBits.length; i++) {
	readBits[i] = 0;
	}
	var x = this.size - 1;
	var y = this.size - 1;
	var dir = -1;
	var off = 0;
	var boff = 0;
	var bit = -1;
	this.firstEncoding = (
	(this.getMaskedBit(x,y) << 3) +
	(this.getMaskedBit(x-1,y) << 2) +
	(this.getMaskedBit(x,y-1) << 1) +
	(this.getMaskedBit(x-1,y-1))
	);
	y -= 2;
	while (x > 0) {
	if (y === 6) { // Skip horizontal timing sequence
	y += dir;
	}

	bit = this.getMaskedBit(x, y);
	if (bit >= 0) {
	boff = off >> 3;
	readBits[boff] += bit << (7 - (off-boff*8));
	off++;
	}

	bit = this.getMaskedBit(x-1, y);
	if (bit >= 0) {
	boff = off >> 3;
	readBits[boff] += bit << (7 - (off-boff*8));
	off++;
	}

	y += dir;

	if (y < 0 \|\| y >= this.size) { // Reverse reading direction at top and bottom of marker
	dir *= -1;
	y += dir;
	x -= 2;
	if (x === 6) { // Skip vertical timing sequence
	x--;
	}
	}
	}
	this.bitLength = off;
	this.bitOffset = 0;
	};

	QRDecoder.prototype.readBits = function(n) {
	if (n === 8 && (this.bitOffset & 7) === 0) {
	var b = this.decodedBits[this.bitOffset >> 3];
	this.bitOffset += 8;
	return b;
	}
	var b = 0;
	var boff = 0;
	for (var i=0; i<n; i++) {
	b <<= 1;
	boff = this.bitOffset >> 3;
	b += (this.decodedBits[boff] >> (7-(this.bitOffset-boff*8))) & 1;
	this.bitOffset++;
	}
	return b;
	};

	QRDecoder.prototype.decodeNumeric = function() {
	var lengthBits = 10;
	if (this.version >= 27) {
	lengthBits = 14;
	} else if (this.version >= 10) {
	lengthBits = 12;
	}
	var length = this.readBits(lengthBits);
	var message = '';
	for (var i=0; i<length/3; i++) {
	var num = this.readBits(10);
	if (num < 10) {
	message += '00'+num.toString();
	} else if (num < 100) {
	message += '0'+num.toString();
	} else {
	message += num.toString();
	}
	}
	return {
	encoding: 1,
	length: length,
	message: message
	};
	};

	QRDecoder.ALPHANUMERIC_TABLE = [
	'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F',
	'G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V',
	'W','X','Y','Z',' ','$','%','*','+','-','.','/',':'
	];

	QRDecoder.prototype.decodeAlphanumeric = function() {
	var lengthBits = 9;
	if (this.version >= 27) {
	lengthBits = 13;
	} else if (this.version >= 10) {
	lengthBits = 11;
	}
	var length = this.readBits(lengthBits);
	var message = '';
	for (var i=0; i<length; i+=2) {
	if (i === length-1) {
	var c1 = this.readBits(6);
	message += QRDecoder.ALPHANUMERIC_TABLE[c1];
	} else {
	var chars = this.readBits(11);
	var c1 = (chars / 45) \| 0;
	message += QRDecoder.ALPHANUMERIC_TABLE[c1];
	var c2 = chars % 45;
	message += QRDecoder.ALPHANUMERIC_TABLE[c2];
	}
	}
	return {
	encoding: 2,
	length: length,
	message: message
	};
	};

	QRDecoder.prototype.decodeKanji = function() {
	var lengthBits = 8;
	if (this.version >= 27) {
	lengthBits = 12;
	} else if (this.version >= 10) {
	lengthBits = 10;
	}
	var length = this.readBits(lengthBits);
	return null;
	};

	QRDecoder.prototype.decodeByte = function() {
	var lengthBits = 8;
	if (this.version >= 27) {
	lengthBits = 16;
	} else if (this.version >= 10) {
	lengthBits = 16;
	}
	var length = this.readBits(lengthBits);
	var message = '';
	for (var i=0; i<length; i++) {
	message += String.fromCharCode(this.readBits(8));
	}
	return {
	encoding: 4,
	length: length,
	message: message
	};
	};


	QRDecoder.prototype.parseBits = function(bits) {
	var packets = [];
	var encoding = this.firstEncoding;
	while (this.bitOffset < this.bitLength) {
	// var raw = [];
	// for (var i=0; i<26; i++) {
	// var s = this.decodedBits[i].toString(16);
	// if (s.length < 2) s = '0' + s;
	// raw.push(s);
	// }
	// console.log(raw.join(" "));
	if (this.bitOffset > 0) {
	encoding = this.readBits(4);
	}
	if (encoding !== 0) {
	var packet;
	switch (encoding) {
	case 1: // Numeric
	packet = this.decodeNumeric();
	break;
	case 2: // Alphanumeric
	packet = this.decodeAlphanumeric();
	break;
	case 4: // Byte
	packet = this.decodeByte();
	break;
	case 8: // Kanji
	packet = this.decodeKanji();
	break;
	case 7: // ECI
	break;
	}
	if (packet) {
	packets.push(packet);
	return packets;
	}
	}
	}
	return packets;
	};

	QRDecoder.prototype.decode = function() {
	if (this.extractQRBits(this.imageData, this)) {
	this.getFormat();
	this.maskAlignmentPatterns();
	this.readDecodedBits();
	return this.parseBits();
	}
	return null;
	};

	QRDecoder.prototype.extractQRBits = function(imageData, bits) {
	var width = imageData.width;
	var height = imageData.height;
	var data = imageData.data;

	var bitMatrix = [];
	for (var y=0; y<height; y++) {
	var bit = 0;
	var rowBits = [];
	bitMatrix.push(rowBits);
	for (var x=0; x<width; x++) {
	var b = data[(ywidth + x)4] < 127 ? 1 : 0;
	if (b !== bit) {
	bit = b;
	rowBits.push(x, b&1);
	}
	}
	}
	while (bitMatrix.length && bitMatrix[0].length === 0) {
	bitMatrix.shift();
	}
	while (bitMatrix.length && bitMatrix[bitMatrix.length-1].length === 0) {
	bitMatrix.pop();
	}
	var rowMatch = function(a, b) {
	if (a === null \|\| a.length !== b.length) {
	return false;
	}
	for (var i=0; i<a.length; i+=2) {
	if (Math.abs( a[i] - b[i] ) > 2) {
	return false;
	}
	if (a[i+1] !== b[i+1]) {
	return false;
	}
	}
	return true;
	};
	var bitRows = [];
	var lastBitRow = null;
	var lastRow = null;
	for (var i=0; i<bitMatrix.length; i++) {
	if (!rowMatch(lastRow, bitMatrix[i])) {
	var row = {length: 0, row: bitMatrix[i]};
	bitRows.push(row);
	lastBitRow = row;
	}
	lastBitRow.length++;
	lastRow = bitMatrix[i];
	}
	var bitRowLengths = [];
	for (var i=0; i<bitRows.length; i++) {
	var l = bitRows[i].length;
	bitRowLengths[l] = (bitRowLengths[l] \|\| 0) + 1;
	}
	var maxCount = 0;
	var maxCountLength = 0;
	for (var i=2; i<bitRowLengths.length; i++) {
	if (bitRowLengths[i] && bitRowLengths[i] > maxCount) {
	maxCountLength = i;
	maxCount = bitRowLengths[i];
	}
	}
	bitRows = bitRows.filter(function(br) {
	return br.length > 1 && Math.abs(br.length - maxCountLength) <= 2;
	});

	var r = bitRows[0].row;
	var w = r[r.length-2] - r[0];
	var stride = w / bitRows.length;
	var off = r[0] + stride/2;

	var sz = bitRows.length;

	if (sz < QRDecoder.MIN_SIZE \|\| sz > QRDecoder.MAX_SIZE \|\| (sz - QRDecoder.MIN_SIZE) % 4 !== 0) {
	return false;
	}

	bits.setSize(sz);

	for (var y=0; y<bitRows.length; y++) {
	var r = bitRows[y].row;
	for (var x=0; x<bitRows.length; x++) {
	var xc = x * stride + off;
	var bit = 0;
	for (var j=r.length-2; j>=0; j-=2) {
	if (r[j] < xc) {
	bit = r[j+1];
	break;
	}
	}
	bits.setBit(x, y, bit);
	}
	}

	return bits;
	};

	</script>

	<script>
	var img = new Image;
	img.src = 'qr.png';
	img.onload = function() {

	var width = Math.floor(this.width),
	height = Math.floor(this.height);

	var canvas = document.createElement('canvas');
	canvas.width = width*3;
	canvas.height = height*2;
	var ctx = canvas.getContext('2d');
	ctx.drawImage(this, 0, 0, width, height);
	var imageData = ctx.getImageData(0, 0, width, height);
	document.body.appendChild(canvas);

	var decoder = new QRDecoder(imageData);

	var tick = function() {
	console.time('qr processing x100');
	var msg = decoder.decode();
	for (var i=0; i<99; i++) {
	decoder.imageData = imageData;
	if (msg[0].message !== decoder.decode()[0].message) {
	throw "Non-stable decoding";
	}
	}
	console.timeEnd('qr processing x100');
	requestAnimationFrame(tick);
	};

	decoder.extractQRBits(imageData, decoder);
	decoder.getFormat();
	console.log("ecc: %d, mask: %d\n", decoder.ecc, decoder.mask);
	decoder.maskAlignmentPatterns();
	ctx.save();
	ctx.translate(width,26);
	for (var y=0; y<decoder.size; y++) {
	for (var x=0; x<decoder.size; x++) {
	var b = decoder.getBit(x,y);
	if (b) {
	ctx.fillStyle = b < 0 ? (b < -1 ? '#ff0000' : '#00ff00') : '#000000';
	ctx.fillRect( x5 , y5, 5, 5);
	}
	}
	}
	for (var i=0; i<10; i++) {
	decoder.decode();
	}
	// decoder.ctx = ctx;
	//ctx.restore();
	console.time('decode');
	var res = decoder.decode();
	console.timeEnd('decode');
	console.log(res);
	ctx.font = '18px sans-serif';
	ctx.fillText(res[0].message, 0, decoder.size * 5 + 20);
	// tick();
	};
	</script>
	</body>
	</html>