findpat.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.
*/


var MIN_SKIP = 3;
var MAX_MODULES = 57;
var INTEGER_MATH_SHIFT = 8;
var CENTER_QUORUM = 2;

qrcode.orderBestPatterns=function(patterns)
		{
			
			function distance( pattern1,  pattern2)
			{
				xDiff = pattern1.X - pattern2.X;
				yDiff = pattern1.Y - pattern2.Y;
				return  Math.sqrt( (xDiff * xDiff + yDiff * yDiff));
			}
			
			/// <summary> Returns the z component of the cross product between vectors BC and BA.</summary>
			function crossProductZ( pointA,  pointB,  pointC)
			{
				var bX = pointB.x;
				var bY = pointB.y;
				return ((pointC.x - bX) * (pointA.y - bY)) - ((pointC.y - bY) * (pointA.x - bX));
			}

			
			// Find distances between pattern centers
			var zeroOneDistance = distance(patterns[0], patterns[1]);
			var oneTwoDistance = distance(patterns[1], patterns[2]);
			var zeroTwoDistance = distance(patterns[0], patterns[2]);
			
			var pointA, pointB, pointC;
			// Assume one closest to other two is B; A and C will just be guesses at first
			if (oneTwoDistance >= zeroOneDistance && oneTwoDistance >= zeroTwoDistance)
			{
				pointB = patterns[0];
				pointA = patterns[1];
				pointC = patterns[2];
			}
			else if (zeroTwoDistance >= oneTwoDistance && zeroTwoDistance >= zeroOneDistance)
			{
				pointB = patterns[1];
				pointA = patterns[0];
				pointC = patterns[2];
			}
			else
			{
				pointB = patterns[2];
				pointA = patterns[0];
				pointC = patterns[1];
			}
			
			// Use cross product to figure out whether A and C are correct or flipped.
			// This asks whether BC x BA has a positive z component, which is the arrangement
			// we want for A, B, C. If it's negative, then we've got it flipped around and
			// should swap A and C.
			if (crossProductZ(pointA, pointB, pointC) < 0.0)
			{
				var temp = pointA;
				pointA = pointC;
				pointC = temp;
			}
			
			patterns[0] = pointA;
			patterns[1] = pointB;
			patterns[2] = pointC;
		}


function FinderPattern(posX, posY,  estimatedModuleSize)
{
	this.x=posX;
	this.y=posY;
	this.count = 1;
	this.estimatedModuleSize = estimatedModuleSize;
	
	this.__defineGetter__("EstimatedModuleSize", function()
	{
		return this.estimatedModuleSize;
	}); 
	this.__defineGetter__("Count", function()
	{
		return this.count;
	});
	this.__defineGetter__("X", function()
	{
		return this.x;
	});
	this.__defineGetter__("Y", function()
	{
		return this.y;
	});
	this.incrementCount = function()
	{
		this.count++;
	}
	this.aboutEquals=function( moduleSize,  i,  j)
		{
			if (Math.abs(i - this.y) <= moduleSize && Math.abs(j - this.x) <= moduleSize)
			{
				var moduleSizeDiff = Math.abs(moduleSize - this.estimatedModuleSize);
				return moduleSizeDiff <= 1.0 || moduleSizeDiff / this.estimatedModuleSize <= 1.0;
			}
			return false;
		}
	
}

function FinderPatternInfo(patternCenters)
{
	this.bottomLeft = patternCenters[0];
	this.topLeft = patternCenters[1];
	this.topRight = patternCenters[2];
	this.__defineGetter__("BottomLeft", function()
	{
		return this.bottomLeft;
	}); 
	this.__defineGetter__("TopLeft", function()
	{
		return this.topLeft;
	}); 
	this.__defineGetter__("TopRight", function()
	{
		return this.topRight;
	}); 
}

function FinderPatternFinder()
{
	this.image=null;
	this.possibleCenters = [];
	this.hasSkipped = false;
	this.crossCheckStateCount = new Array(0,0,0,0,0);
	this.resultPointCallback = null;
	
	this.__defineGetter__("CrossCheckStateCount", function()
	{
		this.crossCheckStateCount[0] = 0;
		this.crossCheckStateCount[1] = 0;
		this.crossCheckStateCount[2] = 0;
		this.crossCheckStateCount[3] = 0;
		this.crossCheckStateCount[4] = 0;
		return this.crossCheckStateCount;
	}); 
	
	this.foundPatternCross=function( stateCount)
		{
			var totalModuleSize = 0;
			for (var i = 0; i < 5; i++)
			{
				var count = stateCount[i];
				if (count == 0)
				{
					return false;
				}
				totalModuleSize += count;
			}
			if (totalModuleSize < 7)
			{
				return false;
			}
			var moduleSize = Math.floor((totalModuleSize << INTEGER_MATH_SHIFT) / 7);
			var maxVariance = Math.floor(moduleSize / 2);
			// Allow less than 50% variance from 1-1-3-1-1 proportions
			return Math.abs(moduleSize - (stateCount[0] << INTEGER_MATH_SHIFT)) < maxVariance && Math.abs(moduleSize - (stateCount[1] << INTEGER_MATH_SHIFT)) < maxVariance && Math.abs(3 * moduleSize - (stateCount[2] << INTEGER_MATH_SHIFT)) < 3 * maxVariance && Math.abs(moduleSize - (stateCount[3] << INTEGER_MATH_SHIFT)) < maxVariance && Math.abs(moduleSize - (stateCount[4] << INTEGER_MATH_SHIFT)) < maxVariance;
		}
	this.centerFromEnd=function( stateCount,  end)
		{
			return  (end - stateCount[4] - stateCount[3]) - stateCount[2] / 2.0;
		}
	this.crossCheckVertical=function( startI,  centerJ,  maxCount,  originalStateCountTotal)
		{
			var image = this.image;
			
			var maxI = qrcode.height;
			var stateCount = this.CrossCheckStateCount;
			
			// Start counting up from center
			var i = startI;
			while (i >= 0 && image[centerJ + i*qrcode.width])
			{
				stateCount[2]++;
				i--;
			}
			if (i < 0)
			{
				return NaN;
			}
			while (i >= 0 && !image[centerJ +i*qrcode.width] && stateCount[1] <= maxCount)
			{
				stateCount[1]++;
				i--;
			}
			// If already too many modules in this state or ran off the edge:
			if (i < 0 || stateCount[1] > maxCount)
			{
				return NaN;
			}
			while (i >= 0 && image[centerJ + i*qrcode.width] && stateCount[0] <= maxCount)
			{
				stateCount[0]++;
				i--;
			}
			if (stateCount[0] > maxCount)
			{
				return NaN;
			}
			
			// Now also count down from center
			i = startI + 1;
			while (i < maxI && image[centerJ +i*qrcode.width])
			{
				stateCount[2]++;
				i++;
			}
			if (i == maxI)
			{
				return NaN;
			}
			while (i < maxI && !image[centerJ + i*qrcode.width] && stateCount[3] < maxCount)
			{
				stateCount[3]++;
				i++;
			}
			if (i == maxI || stateCount[3] >= maxCount)
			{
				return NaN;
			}
			while (i < maxI && image[centerJ + i*qrcode.width] && stateCount[4] < maxCount)
			{
				stateCount[4]++;
				i++;
			}
			if (stateCount[4] >= maxCount)
			{
				return NaN;
			}
			
			// If we found a finder-pattern-like section, but its size is more than 40% different than
			// the original, assume it's a false positive
			var stateCountTotal = stateCount[0] + stateCount[1] + stateCount[2] + stateCount[3] + stateCount[4];
			if (5 * Math.abs(stateCountTotal - originalStateCountTotal) >= 2 * originalStateCountTotal)
			{
				return NaN;
			}
			
			return this.foundPatternCross(stateCount)?this.centerFromEnd(stateCount, i):NaN;
		}
	this.crossCheckHorizontal=function( startJ,  centerI,  maxCount, originalStateCountTotal)
		{
			var image = this.image;
			
			var maxJ = qrcode.width;
			var stateCount = this.CrossCheckStateCount;
			
			var j = startJ;
			while (j >= 0 && image[j+ centerI*qrcode.width])
			{
				stateCount[2]++;
				j--;
			}
			if (j < 0)
			{
				return NaN;
			}
			while (j >= 0 && !image[j+ centerI*qrcode.width] && stateCount[1] <= maxCount)
			{
				stateCount[1]++;
				j--;
			}
			if (j < 0 || stateCount[1] > maxCount)
			{
				return NaN;
			}
			while (j >= 0 && image[j+ centerI*qrcode.width] && stateCount[0] <= maxCount)
			{
				stateCount[0]++;
				j--;
			}
			if (stateCount[0] > maxCount)
			{
				return NaN;
			}
			
			j = startJ + 1;
			while (j < maxJ && image[j+ centerI*qrcode.width])
			{
				stateCount[2]++;
				j++;
			}
			if (j == maxJ)
			{
				return NaN;
			}
			while (j < maxJ && !image[j+ centerI*qrcode.width] && stateCount[3] < maxCount)
			{
				stateCount[3]++;
				j++;
			}
			if (j == maxJ || stateCount[3] >= maxCount)
			{
				return NaN;
			}
			while (j < maxJ && image[j+ centerI*qrcode.width] && stateCount[4] < maxCount)
			{
				stateCount[4]++;
				j++;
			}
			if (stateCount[4] >= maxCount)
			{
				return NaN;
			}
			
			// If we found a finder-pattern-like section, but its size is significantly different than
			// the original, assume it's a false positive
			var stateCountTotal = stateCount[0] + stateCount[1] + stateCount[2] + stateCount[3] + stateCount[4];
			if (5 * Math.abs(stateCountTotal - originalStateCountTotal) >= originalStateCountTotal)
			{
				return NaN;
			}
			
			return this.foundPatternCross(stateCount)?this.centerFromEnd(stateCount, j):NaN;
		}
	this.handlePossibleCenter=function( stateCount,  i,  j)
		{
			var stateCountTotal = stateCount[0] + stateCount[1] + stateCount[2] + stateCount[3] + stateCount[4];
			var centerJ = this.centerFromEnd(stateCount, j); //float
			var centerI = this.crossCheckVertical(i, Math.floor( centerJ), stateCount[2], stateCountTotal); //float
			if (!isNaN(centerI))
			{
				// Re-cross check
				centerJ = this.crossCheckHorizontal(Math.floor( centerJ), Math.floor( centerI), stateCount[2], stateCountTotal);
				if (!isNaN(centerJ))
				{
					var estimatedModuleSize =   stateCountTotal / 7.0;
					var found = false;
					var max = this.possibleCenters.length;
					for (var index = 0; index < max; index++)
					{
						var center = this.possibleCenters[index];
						// Look for about the same center and module size:
						if (center.aboutEquals(estimatedModuleSize, centerI, centerJ))
						{
							center.incrementCount();
							found = true;
							break;
						}
					}
					if (!found)
					{
						var point = new FinderPattern(centerJ, centerI, estimatedModuleSize);
						this.possibleCenters.push(point);
						if (this.resultPointCallback != null)
						{
							this.resultPointCallback.foundPossibleResultPoint(point);
						}
					}
					return true;
				}
			}
			return false;
		}
		
	this.selectBestPatterns=function()
		{
			
			var startSize = this.possibleCenters.length;
			if (startSize < 3)
			{
				// Couldn't find enough finder patterns
				throw "Couldn't find enough finder patterns";
			}
			
			// Filter outlier possibilities whose module size is too different
			if (startSize > 3)
			{
				// But we can only afford to do so if we have at least 4 possibilities to choose from
				var totalModuleSize = 0.0;
				for (var i = 0; i < startSize; i++)
				{
					totalModuleSize +=  this.possibleCenters[i].EstimatedModuleSize;
				}
				var average = totalModuleSize /  startSize;
				for (var i = 0; i < this.possibleCenters.length && this.possibleCenters.length > 3; i++)
				{
					var pattern =  this.possibleCenters[i];
					if (Math.abs(pattern.EstimatedModuleSize - average) > 0.2 * average)
					{
						this.possibleCenters.remove(i);
						i--;
					}
				}
			}
			
			if (this.possibleCenters.Count > 3)
			{
				// Throw away all but those first size candidate points we found.
				//Collections.insertionSort(possibleCenters, new CenterComparator());
				//SupportClass.SetCapacity(possibleCenters, 3);
			}
			
			return new Array( this.possibleCenters[0],  this.possibleCenters[1],  this.possibleCenters[2]);
		}
		
	this.findRowSkip=function()
		{
			var max = this.possibleCenters.length;
			if (max <= 1)
			{
				return 0;
			}
			var firstConfirmedCenter = null;
			for (var i = 0; i < max; i++)
			{
				var center =  this.possibleCenters[i];
				if (center.Count >= CENTER_QUORUM)
				{
					if (firstConfirmedCenter == null)
					{
						firstConfirmedCenter = center;
					}
					else
					{
						// We have two confirmed centers
						// How far down can we skip before resuming looking for the next
						// pattern? In the worst case, only the difference between the
						// difference in the x / y coordinates of the two centers.
						// This is the case where you find top left last.
						this.hasSkipped = true;
						return Math.floor ((Math.abs(firstConfirmedCenter.X - center.X) - Math.abs(firstConfirmedCenter.Y - center.Y)) / 2);
					}
				}
			}
			return 0;
		}
	
	this.haveMultiplyConfirmedCenters=function()
		{
			var confirmedCount = 0;
			var totalModuleSize = 0.0;
			var max = this.possibleCenters.length;
			for (var i = 0; i < max; i++)
			{
				var pattern =  this.possibleCenters[i];
				if (pattern.Count >= CENTER_QUORUM)
				{
					confirmedCount++;
					totalModuleSize += pattern.EstimatedModuleSize;
				}
			}
			if (confirmedCount < 3)
			{
				return false;
			}
			// OK, we have at least 3 confirmed centers, but, it's possible that one is a "false positive"
			// and that we need to keep looking. We detect this by asking if the estimated module sizes
			// vary too much. We arbitrarily say that when the total deviation from average exceeds
			// 5% of the total module size estimates, it's too much.
			var average = totalModuleSize / max;
			var totalDeviation = 0.0;
			for (var i = 0; i < max; i++)
			{
				pattern = this.possibleCenters[i];
				totalDeviation += Math.abs(pattern.EstimatedModuleSize - average);
			}
			return totalDeviation <= 0.05 * totalModuleSize;
		}
		
	this.findFinderPattern = function(image){
		var tryHarder = false;
		this.image=image;
		var maxI = qrcode.height;
		var maxJ = qrcode.width;
		var iSkip = Math.floor((3 * maxI) / (4 * MAX_MODULES));
		if (iSkip < MIN_SKIP || tryHarder)
		{
				iSkip = MIN_SKIP;
		}
		
		var done = false;
		var stateCount = new Array(5);
		for (var i = iSkip - 1; i < maxI && !done; i += iSkip)
		{
			// Get a row of black/white values
			stateCount[0] = 0;
			stateCount[1] = 0;
			stateCount[2] = 0;
			stateCount[3] = 0;
			stateCount[4] = 0;
			var currentState = 0;
			for (var j = 0; j < maxJ; j++)
			{
				if (image[j+i*qrcode.width] )
				{
					// Black pixel
					if ((currentState & 1) == 1)
					{
						// Counting white pixels
						currentState++;
					}
					stateCount[currentState]++;
				}
				else
				{
					// White pixel
					if ((currentState & 1) == 0)
					{
						// Counting black pixels
						if (currentState == 4)
						{
							// A winner?
							if (this.foundPatternCross(stateCount))
							{
								// Yes
								var confirmed = this.handlePossibleCenter(stateCount, i, j);
								if (confirmed)
								{
									// Start examining every other line. Checking each line turned out to be too
									// expensive and didn't improve performance.
									iSkip = 2;
									if (this.hasSkipped)
									{
										done = this.haveMultiplyConfirmedCenters();
									}
									else
									{
										var rowSkip = this.findRowSkip();
										if (rowSkip > stateCount[2])
										{
											// Skip rows between row of lower confirmed center
											// and top of presumed third confirmed center
											// but back up a bit to get a full chance of detecting
											// it, entire width of center of finder pattern
											
											// Skip by rowSkip, but back off by stateCount[2] (size of last center
											// of pattern we saw) to be conservative, and also back off by iSkip which
											// is about to be re-added
											i += rowSkip - stateCount[2] - iSkip;
											j = maxJ - 1;
										}
									}
								}
								else
								{
									// Advance to next black pixel
									do 
									{
										j++;
									}
									while (j < maxJ && !image[j + i*qrcode.width]);
									j--; // back up to that last white pixel
								}
								// Clear state to start looking again
								currentState = 0;
								stateCount[0] = 0;
								stateCount[1] = 0;
								stateCount[2] = 0;
								stateCount[3] = 0;
								stateCount[4] = 0;
							}
							else
							{
								// No, shift counts back by two
								stateCount[0] = stateCount[2];
								stateCount[1] = stateCount[3];
								stateCount[2] = stateCount[4];
								stateCount[3] = 1;
								stateCount[4] = 0;
								currentState = 3;
							}
						}
						else
						{
							stateCount[++currentState]++;
						}
					}
					else
					{
						// Counting white pixels
						stateCount[currentState]++;
					}
				}
			}
			if (this.foundPatternCross(stateCount))
			{
				var confirmed = this.handlePossibleCenter(stateCount, i, maxJ);
				if (confirmed)
				{
					iSkip = stateCount[0];
					if (this.hasSkipped)
					{
						// Found a third one
						done = haveMultiplyConfirmedCenters();
					}
				}
			}
		}
		
		var patternInfo = this.selectBestPatterns();
		qrcode.orderBestPatterns(patternInfo);
		
		return new FinderPatternInfo(patternInfo);
	};
}