jsqrcode/src/perspective-transform.js

a node port of Lazar Laszlo's `jsqrcode` qr code decoder

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();
}

module.exports = PerspectiveTransform