The AffineTransform class can transform a shape (or coordinate system) by translating, scaling, rotating, or shearing it, using any combination of these individual transformation types. Figure 12-5 illustrates the results of various types of coordinate-system transformations on the appearance of one shape, drawn multiple times. Example 12-7 shows the Java code that generates the figure. Figure 12-5. Transformed shapesAn affine transformation is a linear transformation that has two important properties: all straight lines remain straight, and all parallel lines remain parallel. The AffineTransform class can perform a great variety of transformations, but it can't produce nonlinear effects, such as distorting a figure as through a fisheye lens. That kind of effect can be achieved only with image-processing techniques. For a further discussion of transformations and the linear algebra behind the AffineTransform class, see Chapter 4 of Java Foundation Classes in a Nutshell. Example 12-7. Transforms.javapackage je3.graphics; import java.awt.*; import java.awt.geom.*; /** A demonstration of Java2D transformations */ public class Transforms implements GraphicsExample { public String getName( ) { return "Transforms"; } // From GraphicsExample public int getWidth( ) { return 750; } // From GraphicsExample public int getHeight( ) { return 250; } // From GraphicsExample Shape shape; // The shape to draw AffineTransform[ ] transforms; // The ways to transform it String[ ] transformLabels; // Labels for each transform /** * This constructor sets up the Shape and AffineTransform objects we need **/ public Transforms( ) { GeneralPath path = new GeneralPath( ); // Create a shape to draw path.append(new Line2D.Float(0.0f, 0.0f, 0.0f, 100.0f), false); path.append(new Line2D.Float(-10.0f, 50.0f, 10.0f, 50.0f), false); path.append(new Polygon(new int[ ] { -5, 0, 5 }, new int[ ] { 5, 0, 5 }, 3), false); this.shape = path; // Remember this shape // Set up some transforms to alter the shape this.transforms = new AffineTransform[6]; // 1) the identity transform transforms[0] = new AffineTransform( ); // 2) A scale tranform: 3/4 size transforms[1] = AffineTransform.getScaleInstance(0.75, 0.75); // 3) A shearing transform transforms[2] = AffineTransform.getShearInstance(-0.4, 0.0); // 4) A 30 degree clockwise rotation about the origin of the shape transforms[3] = AffineTransform.getRotateInstance(Math.PI*2/12); // 5) A 180 degree rotation about the midpoint of the shape transforms[4] = AffineTransform.getRotateInstance(Math.PI, 0.0, 50.0); // 6) A combination transform transforms[5] = AffineTransform.getScaleInstance(0.5, 1.5); transforms[5].shear(0.0, 0.4); transforms[5].rotate(Math.PI/2, 0.0, 50.0); // 90 degrees // Define names for the transforms transformLabels = new String[ ] { "identity", "scale", "shear", "rotate", "rotate", "combo" }; } /** Draw the defined shape and label, using each transform */ public void draw(Graphics2D g, Component c) { // Define basic drawing attributes g.setColor(Color.black); // black g.setStroke(new BasicStroke(2.0f, BasicStroke.CAP_SQUARE, // 2-pixel BasicStroke.JOIN_BEVEL)); g.setRenderingHint(RenderingHints.KEY_ANTIALIASING, // antialias RenderingHints.VALUE_ANTIALIAS_ON); // Now draw the shape once using each of the transforms we've defined for(int i = 0; i < transforms.length; i++) { AffineTransform save = g.getTransform( ); // save current state g.translate(i*125 + 50, 50); // move origin g.transform(transforms[i]); // apply transform g.draw(shape); // draw shape g.drawString(transformLabels[i], -25, 125); // draw label g.drawRect(-40, -10, 80, 150); // draw box g.setTransform(save); // restore transform } } } |