detector.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 PerspectiveTransform( a11,  a21,  a31,  a12,  a22,  a32,  a13,  a23,  a33)
{
	this.a11 = a11;
	this.a12 = a12;
	this.a13 = a13;
	this.a21 = a21;
	this.a22 = a22;
	this.a23 = a23;
	this.a31 = a31;
	this.a32 = a32;
	this.a33 = a33;
	this.transformPoints1=function( points)
		{
			var max = points.length;
			var a11 = this.a11;
			var a12 = this.a12;
			var a13 = this.a13;
			var a21 = this.a21;
			var a22 = this.a22;
			var a23 = this.a23;
			var a31 = this.a31;
			var a32 = this.a32;
			var a33 = this.a33;
			for (var i = 0; i < max; i += 2)
			{
				var x = points[i];
				var y = points[i + 1];
				var denominator = a13 * x + a23 * y + a33;
				points[i] = (a11 * x + a21 * y + a31) / denominator;
				points[i + 1] = (a12 * x + a22 * y + a32) / denominator;
			}
		}
	this. transformPoints2=function(xValues, yValues)
		{
			var n = xValues.length;
			for (var i = 0; i < n; i++)
			{
				var x = xValues[i];
				var y = yValues[i];
				var denominator = this.a13 * x + this.a23 * y + this.a33;
				xValues[i] = (this.a11 * x + this.a21 * y + this.a31) / denominator;
				yValues[i] = (this.a12 * x + this.a22 * y + this.a32) / denominator;
			}
		}

	this.buildAdjoint=function()
		{
			// Adjoint is the transpose of the cofactor matrix:
			return new PerspectiveTransform(this.a22 * this.a33 - this.a23 * this.a32, this.a23 * this.a31 - this.a21 * this.a33, this.a21 * this.a32 - this.a22 * this.a31, this.a13 * this.a32 - this.a12 * this.a33, this.a11 * this.a33 - this.a13 * this.a31, this.a12 * this.a31 - this.a11 * this.a32, this.a12 * this.a23 - this.a13 * this.a22, this.a13 * this.a21 - this.a11 * this.a23, this.a11 * this.a22 - this.a12 * this.a21);
		}
	this.times=function( other)
		{
			return new PerspectiveTransform(this.a11 * other.a11 + this.a21 * other.a12 + this.a31 * other.a13, this.a11 * other.a21 + this.a21 * other.a22 + this.a31 * other.a23, this.a11 * other.a31 + this.a21 * other.a32 + this.a31 * other.a33, this.a12 * other.a11 + this.a22 * other.a12 + this.a32 * other.a13, this.a12 * other.a21 + this.a22 * other.a22 + this.a32 * other.a23, this.a12 * other.a31 + this.a22 * other.a32 + this.a32 * other.a33, this.a13 * other.a11 + this.a23 * other.a12 +this.a33 * other.a13, this.a13 * other.a21 + this.a23 * other.a22 + this.a33 * other.a23, this.a13 * other.a31 + this.a23 * other.a32 + this.a33 * other.a33);
		}

}

PerspectiveTransform.quadrilateralToQuadrilateral=function( x0,  y0,  x1,  y1,  x2,  y2,  x3,  y3,  x0p,  y0p,  x1p,  y1p,  x2p,  y2p,  x3p,  y3p)
{
	
	var qToS = this.quadrilateralToSquare(x0, y0, x1, y1, x2, y2, x3, y3);
	var sToQ = this.squareToQuadrilateral(x0p, y0p, x1p, y1p, x2p, y2p, x3p, y3p);
	return sToQ.times(qToS);
}

PerspectiveTransform.squareToQuadrilateral=function( x0,  y0,  x1,  y1,  x2,  y2,  x3,  y3)
{
	 dy2 = y3 - y2;
	 dy3 = y0 - y1 + y2 - y3;
	if (dy2 == 0.0 && dy3 == 0.0)
	{
		return new PerspectiveTransform(x1 - x0, x2 - x1, x0, y1 - y0, y2 - y1, y0, 0.0, 0.0, 1.0);
	}
	else
	{
		 dx1 = x1 - x2;
		 dx2 = x3 - x2;
		 dx3 = x0 - x1 + x2 - x3;
		 dy1 = y1 - y2;
		 denominator = dx1 * dy2 - dx2 * dy1;
		 a13 = (dx3 * dy2 - dx2 * dy3) / denominator;
		 a23 = (dx1 * dy3 - dx3 * dy1) / denominator;
		return new PerspectiveTransform(x1 - x0 + a13 * x1, x3 - x0 + a23 * x3, x0, y1 - y0 + a13 * y1, y3 - y0 + a23 * y3, y0, a13, a23, 1.0);
	}
}

PerspectiveTransform.quadrilateralToSquare=function( x0,  y0,  x1,  y1,  x2,  y2,  x3,  y3)
{
	// Here, the adjoint serves as the inverse:
	return this.squareToQuadrilateral(x0, y0, x1, y1, x2, y2, x3, y3).buildAdjoint();
}

function DetectorResult(bits,  points)
{
	this.bits = bits;
	this.points = points;
}


function Detector(image)
{
	this.image=image;
	this.resultPointCallback = null;
	
	this.sizeOfBlackWhiteBlackRun=function( fromX,  fromY,  toX,  toY)
		{
			// Mild variant of Bresenham's algorithm;
			// see http://en.wikipedia.org/wiki/Bresenham's_line_algorithm
			var steep = Math.abs(toY - fromY) > Math.abs(toX - fromX);
			if (steep)
			{
				var temp = fromX;
				fromX = fromY;
				fromY = temp;
				temp = toX;
				toX = toY;
				toY = temp;
			}
			
			var dx = Math.abs(toX - fromX);
			var dy = Math.abs(toY - fromY);
			var error = - dx >> 1;
			var ystep = fromY < toY?1:- 1;
			var xstep = fromX < toX?1:- 1;
			var state = 0; // In black pixels, looking for white, first or second time
			for (var x = fromX, y = fromY; x != toX; x += xstep)
			{
				
				var realX = steep?y:x;
				var realY = steep?x:y;
				if (state == 1)
				{
					// In white pixels, looking for black
					if (this.image[realX + realY*qrcode.width])
					{
						state++;
					}
				}
				else
				{
					if (!this.image[realX + realY*qrcode.width])
					{
						state++;
					}
				}
				
				if (state == 3)
				{
					// Found black, white, black, and stumbled back onto white; done
					var diffX = x - fromX;
					var diffY = y - fromY;
					return  Math.sqrt( (diffX * diffX + diffY * diffY));
				}
				error += dy;
				if (error > 0)
				{
					if (y == toY)
					{
						break;
					}
					y += ystep;
					error -= dx;
				}
			}
			var diffX2 = toX - fromX;
			var diffY2 = toY - fromY;
			return  Math.sqrt( (diffX2 * diffX2 + diffY2 * diffY2));
		}

	
	this.sizeOfBlackWhiteBlackRunBothWays=function( fromX,  fromY,  toX,  toY)
		{
			
			var result = this.sizeOfBlackWhiteBlackRun(fromX, fromY, toX, toY);
			
			// Now count other way -- don't run off image though of course
			var scale = 1.0;
			var otherToX = fromX - (toX - fromX);
			if (otherToX < 0)
			{
				scale =  fromX /  (fromX - otherToX);
				otherToX = 0;
			}
			else if (otherToX >= qrcode.width)
			{
				scale =  (qrcode.width - 1 - fromX) /  (otherToX - fromX);
				otherToX = qrcode.width - 1;
			}
			var otherToY = Math.floor (fromY - (toY - fromY) * scale);
			
			scale = 1.0;
			if (otherToY < 0)
			{
				scale =  fromY /  (fromY - otherToY);
				otherToY = 0;
			}
			else if (otherToY >= qrcode.height)
			{
				scale =  (qrcode.height - 1 - fromY) /  (otherToY - fromY);
				otherToY = qrcode.height - 1;
			}
			otherToX = Math.floor (fromX + (otherToX - fromX) * scale);
			
			result += this.sizeOfBlackWhiteBlackRun(fromX, fromY, otherToX, otherToY);
			return result - 1.0; // -1 because we counted the middle pixel twice
		}
		

	
	this.calculateModuleSizeOneWay=function( pattern,  otherPattern)
		{
			var moduleSizeEst1 = this.sizeOfBlackWhiteBlackRunBothWays(Math.floor( pattern.X), Math.floor( pattern.Y), Math.floor( otherPattern.X), Math.floor(otherPattern.Y));
			var moduleSizeEst2 = this.sizeOfBlackWhiteBlackRunBothWays(Math.floor(otherPattern.X), Math.floor(otherPattern.Y), Math.floor( pattern.X), Math.floor(pattern.Y));
			if (isNaN(moduleSizeEst1))
			{
				return moduleSizeEst2 / 7.0;
			}
			if (isNaN(moduleSizeEst2))
			{
				return moduleSizeEst1 / 7.0;
			}
			// Average them, and divide by 7 since we've counted the width of 3 black modules,
			// and 1 white and 1 black module on either side. Ergo, divide sum by 14.
			return (moduleSizeEst1 + moduleSizeEst2) / 14.0;
		}

	
	this.calculateModuleSize=function( topLeft,  topRight,  bottomLeft)
		{
			// Take the average
			return (this.calculateModuleSizeOneWay(topLeft, topRight) + this.calculateModuleSizeOneWay(topLeft, bottomLeft)) / 2.0;
		}

	this.distance=function( pattern1,  pattern2)
	{
		xDiff = pattern1.X - pattern2.X;
		yDiff = pattern1.Y - pattern2.Y;
		return  Math.sqrt( (xDiff * xDiff + yDiff * yDiff));
	}
	this.computeDimension=function( topLeft,  topRight,  bottomLeft,  moduleSize)
		{
			
			var tltrCentersDimension = Math.round(this.distance(topLeft, topRight) / moduleSize);
			var tlblCentersDimension = Math.round(this.distance(topLeft, bottomLeft) / moduleSize);
			var dimension = ((tltrCentersDimension + tlblCentersDimension) >> 1) + 7;
			switch (dimension & 0x03)
			{
				
				// mod 4
				case 0: 
					dimension++;
					break;
					// 1? do nothing
				
				case 2: 
					dimension--;
					break;
				
				case 3: 
					throw "Error";
				}
			return dimension;
		}

	this.findAlignmentInRegion=function( overallEstModuleSize,  estAlignmentX,  estAlignmentY,  allowanceFactor)
		{
			// Look for an alignment pattern (3 modules in size) around where it
			// should be
			var allowance = Math.floor (allowanceFactor * overallEstModuleSize);
			var alignmentAreaLeftX = Math.max(0, estAlignmentX - allowance);
			var alignmentAreaRightX = Math.min(qrcode.width - 1, estAlignmentX + allowance);
			if (alignmentAreaRightX - alignmentAreaLeftX < overallEstModuleSize * 3)
			{
				throw "Error";
			}
			
			var alignmentAreaTopY = Math.max(0, estAlignmentY - allowance);
			var alignmentAreaBottomY = Math.min(qrcode.height - 1, estAlignmentY + allowance);
			
			var alignmentFinder = new AlignmentPatternFinder(this.image, alignmentAreaLeftX, alignmentAreaTopY, alignmentAreaRightX - alignmentAreaLeftX, alignmentAreaBottomY - alignmentAreaTopY, overallEstModuleSize, this.resultPointCallback);
			return alignmentFinder.find();
		}
		
	this.createTransform=function( topLeft,  topRight,  bottomLeft, alignmentPattern, dimension)
		{
			var dimMinusThree =  dimension - 3.5;
			var bottomRightX;
			var bottomRightY;
			var sourceBottomRightX;
			var sourceBottomRightY;
			if (alignmentPattern != null)
			{
				bottomRightX = alignmentPattern.X;
				bottomRightY = alignmentPattern.Y;
				sourceBottomRightX = sourceBottomRightY = dimMinusThree - 3.0;
			}
			else
			{
				// Don't have an alignment pattern, just make up the bottom-right point
				bottomRightX = (topRight.X - topLeft.X) + bottomLeft.X;
				bottomRightY = (topRight.Y - topLeft.Y) + bottomLeft.Y;
				sourceBottomRightX = sourceBottomRightY = dimMinusThree;
			}
			
			var transform = PerspectiveTransform.quadrilateralToQuadrilateral(3.5, 3.5, dimMinusThree, 3.5, sourceBottomRightX, sourceBottomRightY, 3.5, dimMinusThree, topLeft.X, topLeft.Y, topRight.X, topRight.Y, bottomRightX, bottomRightY, bottomLeft.X, bottomLeft.Y);
			
			return transform;
		}		
	
	this.sampleGrid=function( image,  transform,  dimension)
		{
			
			var sampler = GridSampler;
			return sampler.sampleGrid3(image, dimension, transform);
		}
	
	this.processFinderPatternInfo = function( info)
		{
			
			var topLeft = info.TopLeft;
			var topRight = info.TopRight;
			var bottomLeft = info.BottomLeft;
			
			var moduleSize = this.calculateModuleSize(topLeft, topRight, bottomLeft);
			if (moduleSize < 1.0)
			{
				throw "Error";
			}
			var dimension = this.computeDimension(topLeft, topRight, bottomLeft, moduleSize);
			var provisionalVersion = Version.getProvisionalVersionForDimension(dimension);
			var modulesBetweenFPCenters = provisionalVersion.DimensionForVersion - 7;
			
			var alignmentPattern = null;
			// Anything above version 1 has an alignment pattern
			if (provisionalVersion.AlignmentPatternCenters.length > 0)
			{
				
				// Guess where a "bottom right" finder pattern would have been
				var bottomRightX = topRight.X - topLeft.X + bottomLeft.X;
				var bottomRightY = topRight.Y - topLeft.Y + bottomLeft.Y;
				
				// Estimate that alignment pattern is closer by 3 modules
				// from "bottom right" to known top left location
				var correctionToTopLeft = 1.0 - 3.0 /  modulesBetweenFPCenters;
				var estAlignmentX = Math.floor (topLeft.X + correctionToTopLeft * (bottomRightX - topLeft.X));
				var estAlignmentY = Math.floor (topLeft.Y + correctionToTopLeft * (bottomRightY - topLeft.Y));
				
				// Kind of arbitrary -- expand search radius before giving up
				for (var i = 4; i <= 16; i <<= 1)
				{
					//try
					//{
						alignmentPattern = this.findAlignmentInRegion(moduleSize, estAlignmentX, estAlignmentY,  i);
						break;
					//}
					//catch (re)
					//{
						// try next round
					//}
				}
				// If we didn't find alignment pattern... well try anyway without it
			}
			
			var transform = this.createTransform(topLeft, topRight, bottomLeft, alignmentPattern, dimension);
			
			var bits = this.sampleGrid(this.image, transform, dimension);
			
			var points;
			if (alignmentPattern == null)
			{
				points = new Array(bottomLeft, topLeft, topRight);
			}
			else
			{
				points = new Array(bottomLeft, topLeft, topRight, alignmentPattern);
			}
			return new DetectorResult(bits, points);
		}
		

	
	this.detect=function()
	{
		var info =  new FinderPatternFinder().findFinderPattern(this.image);
			
		return this.processFinderPatternInfo(info); 
	}
}