Java tutorial
/* * Copyright (c) 2004 David Flanagan. All rights reserved. * This code is from the book Java Examples in a Nutshell, 3nd Edition. * It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied. * You may study, use, and modify it for any non-commercial purpose, * including teaching and use in open-source projects. * You may distribute it non-commercially as long as you retain this notice. * For a commercial use license, or to purchase the book, * please visit http://www.davidflanagan.com/javaexamples3. */ //package je3.print; import java.awt.Component; import java.awt.Dimension; import java.awt.Frame; import java.awt.Graphics; import java.awt.JobAttributes; import java.awt.PageAttributes; import java.awt.PrintJob; import java.awt.Toolkit; import java.awt.image.BufferedImage; import javax.swing.JComponent; /** * This class is a Swing component that computes and displays a fractal image * known as a "Julia set". The print() method demonstrates printing with the * Java 1.1 printing API, and is the main point of the example. The code that * computes the Julia set uses complex numbers, and you don't need to understand * it. */ public class JuliaSet1 extends JComponent { // These constants are hard-coded for simplicity double x1 = -1.5, y1 = -1.5, x2 = 1.5, y2 = 1.5; // Region of complex plane int width = 400, height = 400; // Mapped to these pixels double cx, cy; // This complex constant defines the set we display BufferedImage image; // The image we compute // We compute values between 0 and 63 for each point in the complex plane. // This array holds the color values for each of those values. static int[] colors; static { // Static initializer for the colors[] array. colors = new int[64]; for (int i = 0; i < colors.length; i++) { colors[63 - i] = (i * 4 << 16) + (i * 4 << 8) + i * 4; // grayscale // (i*4) ^ ((i * 3)<<6) ^ ((i * 7)<<13); // crazy technicolor } } // No-arg constructor with default values for cx, cy. public JuliaSet1() { this(-1, 0); } // This constructor specifies the {cx,cy} constant. // For simplicity, the other constants remain hardcoded. public JuliaSet1(double cx, double cy) { this.cx = cx; this.cy = cy; setPreferredSize(new Dimension(width, height)); computeImage(); } // This method computes a color value for each pixel of the image void computeImage() { // Create the image image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB); // Now loop through the pixels int i, j; double x, y; double dx = (x2 - x1) / width; double dy = (y2 - y1) / height; for (j = 0, y = y1; j < height; j++, y += dy) { for (i = 0, x = x1; i < width; i++, x += dx) { // For each pixel, call testPoint() to determine a value. // Then map that value to a color and set it in the image. // If testPoint() returns 0, the point is part of the Julia set // and is displayed in black. If it returns 63, the point is // displayed in white. Values in-between are displayed in // varying shades of gray. image.setRGB(i, j, colors[testPoint(x, y)]); } } } // This is the key method for computing Julia sets. For each point z // in the complex plane, we repeatedly compute z = z*z + c using complex // arithmetic. We stop iterating when the magnitude of z exceeds 2 or // after 64 iterations. We return the number of iterations-1. public int testPoint(double zx, double zy) { for (int i = 0; i < colors.length; i++) { // Compute z = z*z + c; double newx = zx * zx - zy * zy + cx; double newy = 2 * zx * zy + cy; zx = newx; zy = newy; // Check magnitude of z and return iteration number if (zx * zx + zy * zy > 4) return i; } return colors.length - 1; } // This method overrides JComponent to display the julia set. // Just scale the image to fit and draw it. public void paintComponent(Graphics g) { g.drawImage(image, 0, 0, getWidth(), getHeight(), this); } // This method demonstrates the Java 1.1 java.awt.PrintJob printing API. // It also demonstrates the JobAttributes and PageAttributes classes // added in Java 1.3. Display the Julia set with ShowBean and use // the Command menu to invoke this print command. public void print() { // Create some attributes objects. This is Java 1.3 stuff. // In Java 1.1, we'd use a java.util.Preferences object instead. JobAttributes jattrs = new JobAttributes(); PageAttributes pattrs = new PageAttributes(); // Set some example attributes: monochrome, landscape mode pattrs.setColor(PageAttributes.ColorType.MONOCHROME); pattrs.setOrientationRequested(PageAttributes.OrientationRequestedType.LANDSCAPE); // Print to file by default jattrs.setDestination(JobAttributes.DestinationType.FILE); jattrs.setFileName("juliaset.ps"); // Look up the Frame that holds this component Component frame = this; while (!(frame instanceof Frame)) frame = frame.getParent(); // Get a PrintJob object to print the Julia set with. // The getPrintJob() method displays a print dialog and allows the user // to override and modify the default JobAttributes and PageAttributes Toolkit toolkit = this.getToolkit(); PrintJob job = toolkit.getPrintJob((Frame) frame, "JuliaSet1", jattrs, pattrs); // We get a null PrintJob if the user clicked cancel if (job == null) return; // Get a Graphics object from the PrintJob. // We print simply by drawing to this Graphics object. Graphics g = job.getGraphics(); // Center the image on the page Dimension pagesize = job.getPageDimension(); // how big is page? Dimension panesize = this.getSize(); // how big is image? g.translate((pagesize.width - panesize.width) / 2, // center it (pagesize.height - panesize.height) / 2); // Draw a box around the Julia Set and label it g.drawRect(-1, -1, panesize.width + 2, panesize.height + 2); g.drawString("Julia Set for c={" + cx + "," + cy + "}", 0, -15); // Set a clipping region g.setClip(0, 0, panesize.width, panesize.height); // Now print the component by calling its paint method this.paint(g); // Finally tell the printer we're done with the page. // No output will be generated if we don't call dispose() here. g.dispose(); } }