1 Chapter 4 2D Graphics: Advanced Topics  To construct custom shape primitives  To apply basic image processing techniques  To create fractal images  To create 2D animation  To perform graphics printing

2 Custom Shapes  GeneralPath –a legacy class that is final  Path2D –has two subclasses: Path2D.Double Path2D.Float (aka GeneralPath)‏ –an abstract class so it can be extended  Area –provides constructive area geometry

3 Shape Interface  The Graphics2D class has methods for drawing and filling Shape objects  Shape is an interface –it has lots of methods  You can implement the interface to create your own Shape class

4 Shape Interface public boolean contains(Rectangle2D rect) public boolean contains(Point2D point) public boolean contains(double x, double y) public boolean contains(double x, double y, double w, double h) public Rectangle getBounds() public Rectangle2D getBounds2D() public PathIterator getPathIterator(AffineTransform at) public PathIterator getPathIterator(AffineTransform at, double flatness) public boolean intersects(Rectangle2D rect)‏ public boolean intersects(double x, double y, double w, double h)

5 A Custom Primitive  The old-fashioned way  Cannot extend the final class GeneralPath  Instead, you can create a wrapper for GeneralPath public class Heart implements Shape { GeneralPath path; public Heart(float x, float y, float w, float h) { path = new GeneralPath(); …

6 A Custom Primitive  Path2D is an abstract class that implements shape –Path2D.Float and Path2D.Double are concrete subclasses  Create new classes using inheritance public class Heart extends Path2D.Double { public Heart(float x, float y, float w, float h) { /* use lineTo, curveTo,etc to build path */

7 Other kinds of Path shapes  For parametric curves, use a loop to compute successive points and do lineTo  Example: Try creating a class to represent a general spirograph curve  Example: superellipse

8 Making Regular Polygons  You could extend the Polygon class and have the constructor generate the vertices for a regular polygon with the desired number of sides

9 Custom Areas  You can also extend the Area class to create a custom shape  See the HeartArea example in the ~tcole/teaching/cs221/demo/ch4 directory on onyx

10 Custom Objects  What do you do if you want to draw objects that consist of multiple shapes and/or curves with specific colors?  Create a class with a method that draws the object. –the method should have a Graphics or Graphics2D parameter –call this method from your paintComponent method

11 Image Processing  AWT – push model  Java 2D – immediate model  JAI – pull model

12 Image Processing Models  push model - source of image controls the loading –e.g. an image coming across the network –AWT classes  immediate model - image data is immediately available –Java2D classes –BufferedImage  pull model – used by Java Advanced Imaging API

13 BufferedImage  An image consists of a set of pixels –each pixel has a value associated with it  A BufferedImage contains –Raster -- holds the pixel values –ColorModel -- specifies how to interpret pixel values  BufferedImage has a create Graphics method which allows you to draw to the image

14 BufferedImage (Java2D)‏ BufferedImage bi = new BufferedImage(300, 400, BufferedImage.TYPE_INT_RGB); Graphics2D g2 = (Graphics2D)(bi.createGraphics()); g2.drawImage(bi, 0, 0, new Component() {}); BufferedImage bi = ImageIO.read(file); Create Read Display

15 Image Types for BufferedImage  BufferedImage has a set of constants to represent different ways of storing color values –TYPE_INT_RGB –TYPE_BYTE_INDEXED –TYPE_BYTE_GRAY

16 ColorModel  An abstract class with methods for translating pixel values into colors plus alpha value –DirectColorModel - RGB colors –IndexedColorModel - for color maps

17 Filtering Images  BufferedImageOp is an interface used for filtering operations  Methods –BufferedImage createCompatibleImage( BufferedImage, ColorModel)‏ –BufferedImage filter(BufferedImage src, BufferedImage dest)‏ –Rectangle2D getBounds2D( BufferedImage src)‏ –Point2D getPoint2D( Point2D srcPt, Point2D destPt)‏

18 BufferedImageOp Implementers  RescaleOp - scale pixel values linearly  LookupOp - use a table to convert pixel values  ConvolveOp - convolute pixel value with thos of neighbors  ColorConvertOp - pixel-by-pixel color conversion  AffineTransformOp - apply the specified transformation to each pixel  Define a custom filter

19 ConvolveOp  Output pixel is a weighted sum of the values of the pixels in some window surrounding the pixel location –use a 3x3 window  A particular convolution is defined by a 3x3 kernel matrix  Common convolutions include smoothing, sharpening and edge detection

20 Example Convolutions  Smoothing averages all the pixels in the window. –reduces contrast  Sharpening(edge detection) accentuate differences in neighboring pixel values 1/ (4)‏ 0 0

21 Low-Level Pixel Manipulation  The Raster class stores an array of pixel values –You can read data for individual pixels but not change them  The Roster class has a subclass called WritableRaster –This class has methods that allow you to change individual pixels and groups of pixels

22 Raster and WritableRaster int[] getPixel(int x, int y, int[] data)‏ float[] getPixel(int x, int y, float[] data)‏ double[] getPixel(int x, int y, double[] data)‏ int[] getPixels(int x, int y, int w, int h, int[] data)‏ float[] getPixels(int x, int y, int w, int h, float[] data)‏ double[] getPixels(int x, int y, int w, int h, double[] data)‏ void setPixel(int x, int y, int[] data)‏ void setPixel(int x, int y, float[] data)‏ void setPixel(int x, int y, double[] data)‏ void setPixels(int x, int y, int w, int h, int[] data)‏ void setPixels(int x, int y, int w, int h, float[] data)‏ void setPixels(int x, int y, int w, int h, double[] data)‏

23 Fractals  Fractals are self-similar structures –look the same on all scales –useful for describing many natural phenomena (coastlines)‏  Koch-Snowflake, Sierpinski Gasket  Mandelbrot and Julia sets  Fractals are often used in computer graphics

24 Raster Manipulation  We are going to plot the Mandelbrot set as an example of writing directly to an image raster  To understand the program, we need a little background –complex numbers –bitwise operators

25 Complex Numbers  Complex numbers are numbers which include numbers like i which is the square root of -1  A complex number has two parts z = x + i y  We visualize the complex plane just like a 2D space with the real part along the x axis and the imaginary part along the y axis

26 Complex Arithmetic  The standard arithmetic operations are defined for complex numbers –z 1 + z 2 = (x 1 + x 2 ) + i (y 1 + y 2 )‏ –z 1 * z 2 = (x 1 x 2 - y 1 y 2 ) + i (x 1 y 2 + y 1 x 2 )‏  The magnitude of a complex number is –((x + i y)(x - i y)) 1/2 = (x 2 + y 2 ) 1/2

27 Bitwise Operators  Bitwise operators combine two integers using bit-by-bit logical operations & bitwise AND - use to mask bits | bitwise OR >> binary operator to shift bits right << shift bits left ^ exclusive or (XOR)‏ ~ complement

28 Mandelbrot Set  Consider the following iterative equation –z n+1 = z n 2 + cwhere c is a complex constant  The Mandelbrot set is the set of values of c for which this iteration sequence is bounded –if the magnitude of z ever exceeds 2 for a given c, that value of c is not in the set

09/19/08 Animation  To make the content of a panel dynamic, we can animate it  An animation consists of a series of rendered images (called frames)  Frame rate should be at least 60 frames per second to make the animation smooth  Frame rate is limited by the time it takes to render the image

09/19/08 Animation Process  You need a way to make something happen at regular intervals –Change some parameter used by the paintComponent method –call repaint() or revalidate() to cause paintComponent to be called

09/19/08 Two Approaches  Create a separate thread of execution to handle changes with time –Swing components are not thread-safe so direct manipulation of the component is not a good idea –Animation logic is performed in a separate thread  Use the Timer class

09/19/08 Threads  Threads allow a program to divide itself into parts that run independently and simultaneously –threads are not separate processes  The run-time system for Java always has multiple threads running  Create new threads by extending the Thread class or implementing the Runnable interface –Since our classes already extend another class, use the Runnable interface

09/19/08 Implementing Runnable public class PanelClass extends JPanel implements Runnable { public PanelClass() { //create and start thread } public void run() {…} }

34 Animation: Multi-threading Outline of a typical multi-threading animation public void paintComponent(Graphics g) { } public void run() { while(true) { repaint(); try { Thread.sleep(sleepTime); } catch (InterruptedException ex) {} }

09/19/08 Timer class  Timer is a Swing Component –delay can be set –generates an ActionEvent after each delay period –register a Listener to respond to the event

36 Animation: Timer Timer timer = new Timer(period, listener); timer.start(); public void actionPerformed(ActionEvent event) { } Outline of an animation with Timer

37 Cellular Automata The iteration of the system proceeds by assigning the next state of each cell based on the previous configuration. Each cell follows the same set of rules and the new state depends only upon the current states of the same cell and its neighbors. Example: A cell is black if exactly one of its neighbors in the current configuration is black

09/19/08 Conway's Game of Life  Birth: a dead cell becomes live if it has exactly 3 live neighbors  Survival: a live cell remains live if it has 2 or 3 neighbors  Death: a live cell with less than 2 or more than 3 neighbors dies

09/19/08 Rendering to Output Devices  Tha Java2D API was defined to do device- independent rendering  Provides access to three output devices –Screen using a Component like JPanel –Image using a BufferedImage –Printer using Printable interface and PrintJob class

40 Classes used in Printing  PrinterJob –getPrintJob –printDialog –setPrintable –print  Printable –Print  PageFormat –getOrientation –getWidth –getHeight –getImageableX –getImageableY –getImageableWidth –getImageableHeight