Add addition method to matrix class

Add method, test, new constructor and improve existing javadocs

Author: Samuel Huylebroeck

kernel/src/main/java/com/itextpdf/kernel/geom/Matrix.java

@@ -100,14 +100,32 @@ public Matrix(float tx, float ty) {
         vals[I32] = ty;
     }
 
+    /**
+     * Creates a Matrix with 9 specified entries
+     * @param e11 element at position (1,1)
+     */
+    public Matrix(float e11, float e12, float e13, float e21, float e22, float e23, float e31, float e32, float e33){
+        vals[I11] = e11;
+        vals[I12] = e12;
+        vals[I13] = e13;
+        vals[I21] = e21;
+        vals[I22] = e22;
+        vals[I23] = e23;
+        vals[I31] = e31;
+        vals[I32] = e32;
+        vals[I33] = e33;
+    }
+
     /**
      * Creates a Matrix with 6 specified entries
-     * @param a
-     * @param b
-     * @param c
-     * @param d
-     * @param e
-     * @param f
+     * The third column will always be [0 0 1]
+     * (row, column)
+     * @param a element at (1,1)
+     * @param b element at (1,2)
+     * @param c element at (2,1)
+     * @param d element at (2,2)
+     * @param e element at (3,1)
+     * @param f element at (3,2)
      */
     public Matrix(float a, float b, float c, float d, float e, float f){
         vals[I11] = a;
@@ -162,6 +180,32 @@ public Matrix multiply(Matrix by){
         return rslt;
     }
 
+    /**
+     * adds a matrix from this matrix and returns the results
+     * @param arg the matrix to subtract from this matrix
+     * @return a Matrix object
+     */
+    public Matrix add(Matrix arg){
+        Matrix rslt = new Matrix();
+
+        float[] a = vals;
+        float[] b = arg.vals;
+        float[] c = rslt.vals;
+
+        c[I11] = a[I11]+b[I11];
+        c[I12] = a[I12]+b[I12];
+        c[I13] = a[I13]+b[I13];
+        c[I21] = a[I21]+b[I21];
+        c[I22] = a[I22]+b[I22];
+        c[I23] = a[I23]+b[I23];
+        c[I31] = a[I31]+b[I31];
+        c[I32] = a[I32]+b[I32];
+        c[I33] = a[I33]+b[I33];
+
+
+        return rslt;
+    }
+
     /**
      * Subtracts a matrix from this matrix and returns the results
      * @param arg the matrix to subtract from this matrix

kernel/src/test/java/com/itextpdf/kernel/geom/MatrixTest.java

@@ -69,4 +69,24 @@ public void testDeterminant(){
         Assert.assertEquals(-2f, m.getDeterminant(), .001f);
     }
 
+    @Test
+    public void testSubtract() throws Exception{
+        Matrix m1 = new Matrix(1, 2, 3, 4, 5, 6);
+        Matrix m2 = new Matrix(6, 5, 4, 3, 2, 1);
+        Matrix shouldBe = new Matrix(-5, -3,0, -1, 1,0, 3, 5,0);
+
+        Matrix rslt = m1.subtract(m2);
+        Assert.assertEquals(shouldBe, rslt);
+    }
+
+    @Test
+    public void testAdd() throws Exception{
+        Matrix m1 = new Matrix(1, 2, 3, 4, 5, 6);
+        Matrix m2 = new Matrix(6, 5, 4, 3, 2, 1);
+        Matrix shouldBe = new Matrix(7, 7,0, 7, 7,0, 7, 7,2);
+
+        Matrix rslt = m1.add(m2);
+        Assert.assertEquals(shouldBe, rslt);
+    }
+
 }