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The Adobe Experience Manager SDK
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/*
*
*	File: Matrix.java
*
*
*	ADOBE CONFIDENTIAL
*	___________________
*
*	Copyright 2004-2005 Adobe Systems Incorporated
*	All Rights Reserved.
*
*	NOTICE: All information contained herein is, and remains the property of
*	Adobe Systems Incorporated and its suppliers, if any. The intellectual
*	and technical concepts contained herein are proprietary to Adobe Systems
*	Incorporated and its suppliers and may be covered by U.S. and Foreign
*	Patents, patents in process, and are protected by trade secret or
*	copyright law. Dissemination of this information or reproduction of this
*	material is strictly forbidden unless prior written permission is obtained
*	from Adobe Systems Incorporated.
*
*/
package com.adobe.fontengine.font;

/**
 * A 2x3 "Postscript style" coordinate matrix (a 2D transformation and shift).
 * 
 * Synchronization
 * 
 * These objects are immutable.
 */
final public class Matrix {
    /** a constant Matrix representing the identity transformation */
    public final static Matrix IDENTITY_MATRIX = new Matrix(1,0,0,1,0,0);
    
    public final double a;
    public final double b;
    public final double c;
    public final double d;
    public final double tx;
    public final double ty;
    
    /**
     * Creates a matrix from either a 4 or 6 element array representing a matrix.
     * If there are 4 elements, tx and ty are set to 0. 
     * 
     * @param matrix contains the matrix elements in the following order: a, b, c, d, tx, ty
     */
    public Matrix(double[] matrix)
    {
        a = matrix[0];
        b = matrix[1];
        c = matrix[2];
        d = matrix[3];
        tx = matrix.length > 4 ? matrix[4]:0;
        ty = matrix.length > 5 ? matrix[5]:0;
    }
    
    public Matrix(double a, double b, double c, double d, double tx, double ty)
    {
        this.a = a;
        this.b = b;
        this.c = c;
        this.d = d;
        this.tx = tx;
        this.ty = ty;
    }
    
    /**
     * Returns true iff this is very close to representing the identity transformation.
     */
    public boolean isIdentity()
    {
        return (Math.abs(a - 1) < 0.001 && Math.abs(d - 1) < 0.001 
                && Math.abs(b) < 0.001 && Math.abs(c) < 0.001
                && Math.abs(tx) < 0.001 && Math.abs(ty) < 0.001);
    }
    
    /**
     * Checks whether 'inverse' is the inverse of this matrix.
     * @param inverse the matrix to be compared
     * @return true iff this * inverse ~= IDENTITY_MATRIX
     */
    public boolean isInverse(Matrix inverse)
    {
        Matrix res = multiply(inverse);
        
        return res.isIdentity();
    }
    
    /** Computes this * multiplier and returns the resulting matrix. */
    public Matrix multiply(Matrix multiplier)
    {
        double aRes,bRes,cRes,dRes,txRes,tyRes;
        aRes = this.a * multiplier.a + this.b * multiplier.c;
        bRes = this.a * multiplier.b + this.b * multiplier.d;
        cRes = this.c * multiplier.a + this.d * multiplier.c;
        dRes = this.c * multiplier.b + this.d * multiplier.d;
        txRes = this.tx * multiplier.a + this.ty * multiplier.c + multiplier.tx;
        tyRes = this.tx * multiplier.b + this.ty * multiplier.d + multiplier.ty;
        return new Matrix(aRes,bRes,cRes,dRes,txRes,tyRes);
        
    }
    
    /** Computes this * multiplier and returns the resulting matrix. */
    public Matrix multiply (double multiplier) {
      return new Matrix (a * multiplier, b * multiplier, c * multiplier,
          d * multiplier, tx * multiplier, ty * multiplier);
    }
    
    /** computes p * this and returns the result in p */
    public void applyToPoint(Point p)
    {
        // shortcut the process if we are looking at the identity matrix.
        if (this.equals(IDENTITY_MATRIX))
            return;
        
        double origX = p.x;
        double origY = p.y;
        
        p.x = origX * a + origY * c + tx;
        p.y = origX * b + origY * d + ty;
    }
    
    /** computes [x y] * this and returns the resulting x value */
    public double applyToXYGetX(double x, double y)
    {
        return x*a + y*c + tx;
    }
    
    /** computes [x y] * this and returns the resulting y value */
    public double applyToXYGetY(double x, double y)
    {
        return x*b + y*d + ty;
    }
    
}