bmparser.js

/*
  Ported to JavaScript by Lazar Laszlo 2011 
  
  lazarsoft@gmail.com, www.lazarsoft.info
  
*/

/*
*
* Copyright 2007 ZXing authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
*      http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/


function BitMatrixParser(bitMatrix)
{
	var dimension = bitMatrix.Dimension;
	if (dimension < 21 || (dimension & 0x03) != 1)
	{
		throw "Error BitMatrixParser";
	}
	this.bitMatrix = bitMatrix;
	this.parsedVersion = null;
	this.parsedFormatInfo = null;
	
	this.copyBit=function( i,  j,  versionBits)
	{
		return this.bitMatrix.get_Renamed(i, j)?(versionBits << 1) | 0x1:versionBits << 1;
	}
	
	this.readFormatInformation=function()
	{
			if (this.parsedFormatInfo != null)
			{
				return this.parsedFormatInfo;
			}
			
			// Read top-left format info bits
			var formatInfoBits = 0;
			for (var i = 0; i < 6; i++)
			{
				formatInfoBits = this.copyBit(i, 8, formatInfoBits);
			}
			// .. and skip a bit in the timing pattern ...
			formatInfoBits = this.copyBit(7, 8, formatInfoBits);
			formatInfoBits = this.copyBit(8, 8, formatInfoBits);
			formatInfoBits = this.copyBit(8, 7, formatInfoBits);
			// .. and skip a bit in the timing pattern ...
			for (var j = 5; j >= 0; j--)
			{
				formatInfoBits = this.copyBit(8, j, formatInfoBits);
			}
			
			this.parsedFormatInfo = FormatInformation.decodeFormatInformation(formatInfoBits);
			if (this.parsedFormatInfo != null)
			{
				return this.parsedFormatInfo;
			}
			
			// Hmm, failed. Try the top-right/bottom-left pattern
			var dimension = this.bitMatrix.Dimension;
			formatInfoBits = 0;
			var iMin = dimension - 8;
			for (var i = dimension - 1; i >= iMin; i--)
			{
				formatInfoBits = this.copyBit(i, 8, formatInfoBits);
			}
			for (var j = dimension - 7; j < dimension; j++)
			{
				formatInfoBits = this.copyBit(8, j, formatInfoBits);
			}
			
			this.parsedFormatInfo = FormatInformation.decodeFormatInformation(formatInfoBits);
			if (this.parsedFormatInfo != null)
			{
				return this.parsedFormatInfo;
			}
			throw "Error readFormatInformation";	
	}
	this.readVersion=function()
		{
			
			if (this.parsedVersion != null)
			{
				return this.parsedVersion;
			}
			
			var dimension = this.bitMatrix.Dimension;
			
			var provisionalVersion = (dimension - 17) >> 2;
			if (provisionalVersion <= 6)
			{
				return Version.getVersionForNumber(provisionalVersion);
			}
			
			// Read top-right version info: 3 wide by 6 tall
			var versionBits = 0;
			var ijMin = dimension - 11;
			for (var j = 5; j >= 0; j--)
			{
				for (var i = dimension - 9; i >= ijMin; i--)
				{
					versionBits = this.copyBit(i, j, versionBits);
				}
			}
			
			this.parsedVersion = Version.decodeVersionInformation(versionBits);
			if (this.parsedVersion != null && this.parsedVersion.DimensionForVersion == dimension)
			{
				return this.parsedVersion;
			}
			
			// Hmm, failed. Try bottom left: 6 wide by 3 tall
			versionBits = 0;
			for (var i = 5; i >= 0; i--)
			{
				for (var j = dimension - 9; j >= ijMin; j--)
				{
					versionBits = this.copyBit(i, j, versionBits);
				}
			}
			
			this.parsedVersion = Version.decodeVersionInformation(versionBits);
			if (this.parsedVersion != null && this.parsedVersion.DimensionForVersion == dimension)
			{
				return this.parsedVersion;
			}
			throw "Error readVersion";
		}
	this.readCodewords=function()
		{
			
			var formatInfo = this.readFormatInformation();
			var version = this.readVersion();
			
			// Get the data mask for the format used in this QR Code. This will exclude
			// some bits from reading as we wind through the bit matrix.
			var dataMask = DataMask.forReference( formatInfo.DataMask);
			var dimension = this.bitMatrix.Dimension;
			dataMask.unmaskBitMatrix(this.bitMatrix, dimension);
			
			var functionPattern = version.buildFunctionPattern();
			
			var readingUp = true;
			var result = new Array(version.TotalCodewords);
			var resultOffset = 0;
			var currentByte = 0;
			var bitsRead = 0;
			// Read columns in pairs, from right to left
			for (var j = dimension - 1; j > 0; j -= 2)
			{
				if (j == 6)
				{
					// Skip whole column with vertical alignment pattern;
					// saves time and makes the other code proceed more cleanly
					j--;
				}
				// Read alternatingly from bottom to top then top to bottom
				for (var count = 0; count < dimension; count++)
				{
					var i = readingUp?dimension - 1 - count:count;
					for (var col = 0; col < 2; col++)
					{
						// Ignore bits covered by the function pattern
						if (!functionPattern.get_Renamed(j - col, i))
						{
							// Read a bit
							bitsRead++;
							currentByte <<= 1;
							if (this.bitMatrix.get_Renamed(j - col, i))
							{
								currentByte |= 1;
							}
							// If we've made a whole byte, save it off
							if (bitsRead == 8)
							{
								result[resultOffset++] =  currentByte;
								bitsRead = 0;
								currentByte = 0;
							}
						}
					}
				}
				readingUp ^= true; // readingUp = !readingUp; // switch directions
			}
			if (resultOffset != version.TotalCodewords)
			{
				throw "Error readCodewords";
			}
			return result;
		}
}