Affine Transform Example

AffineTransformTests.java

package document.transform;

import com.itextpdf.kernel.geom.AffineTransform;
import com.itextpdf.kernel.geom.Point;
import junit.framework.TestCase;
import org.junit.Test;


public class AffineTransformTests extends TestCase {


    /**
     * Test move a rectangle, move C to (0, 0)
     *  ------------------------------------
     *  |                                   |
     *  |                                   |
     *  |                                   |
     *  |                                   |
     *  |                                   |
     *  |    A(4,8) .        . B(8,8)       |
     *  |                                   |
     *  |                                   |
     *  |                                   |
     *  |    C(4,4) .        . D(8,4)       |
     *  |                                   |
     *  |                                   |
     *  |                                   |
     *  |                                   |
     *  ------------------------------------
     *
     * @throws Exception
     */
    @Test
    public void testMove() throws Exception{
        Point A = new Point(4, 8);
        Point B = new Point(8, 8);
        Point C = new Point(4,4);
        Point D = new Point(8, 4);

        AffineTransform transformer = AffineTransform.getTranslateInstance(-C.x, -C.y);

        Point newA = transformer.transform(A, null);
        Point newB = transformer.transform(B, null);
        Point newC = transformer.transform(C, null);
        Point newD = transformer.transform(D, null);

        assertEquals(0.0, newA.x,0.01);
        assertEquals(4.0, newA.y,0.01);

        assertEquals(4.0, newB.x,0.01);
        assertEquals(4.0, newB.y,0.01);

        assertEquals(0.0, newC.x,0.01);
        assertEquals(0.0, newC.y,0.01);

        assertEquals(4.0, newD.x,0.01);
        assertEquals(0.0, newD.y,0.01);
    }


    /**
     * Test Scale for a rectangle at the right top position, scale(x,y) = (1.5, 1.5)
     *  ------------------------------------
     *  |                                   |
     *  |                                   |
     *  |                                   |
     *  |                                   |
     *  |                                   |
     *  |    A(4,8) .        . B(8,8)       |
     *  |                                   |
     *  |                                   |
     *  |                                   |
     *  |    C(4,4) .        . D(8,4)       |
     *  |                                   |
     *  |                                   |
     *  |                                   |
     *  |                                   |
     *  ------------------------------------
     *
     * @throws Exception
     */
    @Test
    public void testScaleRightTop() throws Exception{
        Point A = new Point(4, 8);
        Point B = new Point(8, 8);
        Point C = new Point(4,4);
        Point D = new Point(8, 4);

        AffineTransform transformer = AffineTransform.getTranslateInstance(-C.x, -C.y);
        transformer.preConcatenate(AffineTransform.getScaleInstance(1.5, 1.5));
        transformer.preConcatenate(AffineTransform.getTranslateInstance(C.x, C.y));

        Point newA = transformer.transform(A, null);
        Point newB = transformer.transform(B, null);
        Point newC = transformer.transform(C, null);
        Point newD = transformer.transform(D, null);
        
        assertEquals(4.0, newA.x, 0.01);
        assertEquals(10.0, newA.y, 0.01);

        assertEquals(10.0, newB.x, 0.01);
        assertEquals(10.0, newB.y, 0.01);

        assertEquals(4.0, newC.x, 0.01);
        assertEquals(4.0, newC.y, 0.01);

        assertEquals(10.0, newD.x, 0.01);
        assertEquals(4.0, newD.y, 0.01);
    }

    /**
     * Test Scale for a rectangle at the right bottom position, scale(x,y) = (1.5, 1.5)
     *  ------------------------------------
     *  |                                   |
     *  |                                   |
     *  |                                   |
     *  |                                   |
     *  |                                   |
     *  |    A(4,8) .        . B(8,8)       |
     *  |                                   |
     *  |                                   |
     *  |                                   |
     *  |    C(4,4) .        . D(8,4)       |
     *  |                                   |
     *  |                                   |
     *  |                                   |
     *  |                                   |
     *  ------------------------------------
     *
     * @throws Exception
     */
    @Test
    public void testScaleRightBottom() throws Exception{
        Point A = new Point(4, 8);
        Point B = new Point(8, 8);
        Point C = new Point(4,4);
        Point D = new Point(8, 4);

        AffineTransform transformer = AffineTransform.getTranslateInstance(-D.x, -D.y);
        transformer.preConcatenate(AffineTransform.getScaleInstance(1.5, 1.5));
        transformer.preConcatenate(AffineTransform.getTranslateInstance(D.x, D.y));

        Point newA = transformer.transform(A, null);
        Point newB = transformer.transform(B, null);
        Point newC = transformer.transform(C, null);
        Point newD = transformer.transform(D, null);

        assertEquals(2.0, newA.x, 0.01);
        assertEquals(10.0, newA.y, 0.01);

        assertEquals(8.0, newB.x, 0.01);
        assertEquals(10.0, newB.y, 0.01);

        assertEquals(2.0, newC.x, 0.01);
        assertEquals(4.0, newC.y, 0.01);

        assertEquals(8.0, newD.x, 0.01);
        assertEquals(4.0, newD.y, 0.01);
    }

    /**
     * Test rotate a rectangle at the left top position, Counter Clock Wise 90 degree
     *  ------------------------------------
     *  |                                   |
     *  |                                   |
     *  |                                   |
     *  |                                   |
     *  |                                   |
     *  |    A(4,8) .        . B(8,8)       |
     *  |                                   |
     *  |                                   |
     *  |                                   |
     *  |    C(4,4) .        . D(8,4)       |
     *  |                                   |
     *  |                                   |
     *  |                                   |
     *  |                                   |
     *  ------------------------------------
     *
     * @throws Exception
     */
    @Test
    public void testRoteteLeftBottomCCW90() throws Exception{
        Point A = new Point(4, 8);
        Point B = new Point(8, 8);
        Point C = new Point(4,4);
        Point D = new Point(8, 4);

        AffineTransform transformer = AffineTransform.getTranslateInstance(-A.x, -A.y);
        transformer.preConcatenate(AffineTransform.getRotateInstance(Math.PI/2));
        transformer.preConcatenate(AffineTransform.getTranslateInstance(A.x, A.y));

        Point newA = transformer.transform(A, null);
        Point newB = transformer.transform(B, null);
        Point newC = transformer.transform(C, null);
        Point newD = transformer.transform(D, null);

        assertEquals(4.0, newA.x, 0.01);
        assertEquals(8.0, newA.y, 0.01);

        assertEquals(4.0, newB.x, 0.01);
        assertEquals(12, newB.y, 0.01);

        assertEquals(8.0, newC.x, 0.01);
        assertEquals(8.0, newC.y, 0.01);

        assertEquals(8.0, newD.x, 0.01);
        assertEquals(12.0, newD.y, 0.01);
    }
}