Graphics Programming with Java 2D

Java 2D API  Shapes, text, and images  A uniform mechanism for performing transformations  rotation and scaling, on objects.  A wide array of presentation devices such as  displays and printers,  image formats and encodings,  color spaces,  rendering techniques and effects.  Comprehensive text and font handling,  color support

Rendering  The process of taking a collection of shapes, text, and images &  Figure out what colors the pixels should be on a screen or printer.  In the Java 2D API, the Graphics2D class is the rendering engine:  the Graphics2D object contains state attributes, such as color &  applies these attributes to the primitives when rendering them to various output devices.

The attributes of Graphics2D object  Paint: represents the color or pattern that the primitive will be when it is rendered.  Stroke: describes the line style of the outline of the shape  Font: the font of the text to be rendered  Rendering hint: suggests how a primitive should be rendered, such as whether a faster or more accurate algorithm should be used.  Transform: represents the mapping from user space to device space and additional graphic transforms, such as rotate and scale, to be applied to particular primitives.  Composite: defines how the overlapping parts of two graphic objects should be rendered  Clip: identifies the part of a primitive that is to be rendered

The Rendering Process

What is a rasterizer?  Takes ideal shapes and produces coverage values for each pixel.  The coverage values represent how much of each pixel is covered by the shape.  These coverage values are called alpha values.  Each pixel has its own alpha value which indicates the transparency of the pixel

Is it possible to use native rasterizer?  Java 2D does not use a native rasterizer for rendering fonts  Uses the T2K font rasterizer from Type Solutions  By allowing T2K to rasterize fonts, the Java 2D API isn't dependent on native rasterizers for the scalable outline fonts that it supports  can result in more consistent metrics display across different platforms and between on-screen and off-screen rendering

The Java 2D API classes The classes that represent predetermined shapes. Arc2D: an arc defined by a bounding rectangle, start angle, angular extent, and a closure type CubicCurve2D: a cubic parametric curve segment. Ellipse2D: an ellipse defined by a bounding rectangle. Line2D: a line segment in (x, y) coordinate space. Point2D: a location in (x,y) coordinate space. QuadCurve2D: a quadratic parametric curve segment. Rectangle2D: a rectangle defined by a location (x, y) and dimension (w x h) RoundRectangle2D: a rectangle with rounded corners defined by a location (x, y), a dimension (w x h), and the width and height of the corner arc.

Defining odd shapes Two classes allow us to to define odd shapes  GeneralPath  Shapes must be created segment by segment,  We can combine straight lines and curved lines into a single shape.  Area  Supports constructive area geometry  allows us to combine two shapes to create another shape, by adding or intersecting the shapes, subtracting one shape from another by subtracting the intersection of the shapes.

Complex Shapes from Geometry Primitives  Constructive Area Geometry (CAG) is the process of creating new geometric shapes by performing boolean operations on existing ones.  A special type of Shape called an Area supports boolean operations.  We can construct an Area from any Shape.

Areas examples Areas support the following boolean operations: Union Subtraction Intersection Exclusive-or (XOR)

package untitled71; import javax.swing.UIManager; import java.awt.*; import java.awt.event.*; import java.awt.font.*; import java.awt.geom.*; import javax.swing.*; // This applet renders a pear, using CAG methods: add, intersect, and subtract. public class Pear extends JApplet { Ellipse2D.Double circle, oval, leaf, stem; Area circ, ov, leaf1, leaf2, st1, st2; public void init() { circle = new Ellipse2D.Double(); oval = new Ellipse2D.Double(); leaf = new Ellipse2D.Double(); stem = new Ellipse2D.Double(); circ = new Area(circle); ov = new Area(oval); leaf1 = new Area(leaf); leaf2 = new Area (leaf); st1 = new Area (stem); st2 = new Area (stem); setBackground (Color.white); }

public void paint (Graphics g) { Graphics2D g2 = (Graphics2D) g; Dimension d = getSize() int w = d.width; int h = d.height; double ew = w/2; double eh = h/2; g2.setColor(Color.green); // Creates the first leaf by filling the intersection of two Area objects created from an ellipse. leaf.setFrame(ew-16, eh-29, 15.0, 15.0); leaf1 = new Area (leaf); leaf.setFrame(ew-14, eh-47, 30.0, 30.0); leaf2 = new Area (leaf); leaf1.intersect (leaf2); g2.fill(leaf1); // Creates the second leaf. leaf.setFrame (ew+1, eh-29, 15.0, 15.0); leaf1 = new Area (leaf); leaf2.intersect (leaf1); g2.fill(leaf2);

g2.setColor(Color.black); /** Creates the stem by filling the Area resulting from the subtraction of two Area objects created from an ellipse.**/ stem.setFrame (ew, eh-42, 40.0, 40.0); st1 = new Area (stem); stem.setFrame(ew+3, eh-47, 50.0, 50.0); st2 = new Area (stem); st1.subtract( st2); g2.fill(st1); g2.setColor(Color.yellow); / ** Creates the pear itself by filling the Area resulting from the union of two Area objects created by two different ellipses **/ circle.setFrame(ew-25, eh, 50.0, 50.0); oval.setFrame(ew-19, eh-20, 40.0, 70.0); circ = new Area (circle); ov = new Area (oval); circ.add(ov); g2.fill(circ); }

public static void main (String s[]) { JFrame f = new JFrame ("Pear"); f.addWindowListener (new WindowAdapter() { public void windowClosing (WindowEvent e) { System.exit(0);} } ) ; JApplet applet = new Pear(); f.getContentPane(). add ("Center", applet); applet.init(); f.pack(); f.setSize (new Dimension(150,200)); f.show(); }

java.awt.font.* Class Diagrams  Font Interfaces: MultipleMaster, OpenType Classes: java.awt.Font, FontRenderContext, LineMetrics, java.awt.FontMetrics  TextLayout Classes: TextHitInfo, TextLayout, TextLayout.CaretPolicy, LineBreakMeasurer, TextMeasurer  Attribute Classes: java.text.AttributedCharacterIterator.Attribute, GraphicAttribute, ImageGraphicAttribute, TextAttribute, ShapeGraphicAttribute, NumericShaper, TransformAttribute  Glyph Classes: GlyphMetrics, GlyphVector, GlyphJustificationInfo

java.awt.geom.* Class Diagrams  Shapes Interfaces: java.awt.Shape  Lines Interfaces: java.awt.Shape Classes: QuadCurve2D, QuadCurve2D.Double, QuadCurve2D.Float, CubicCurve2D, Line2D, CubicCurve2D.Double, Line2D.Double, CubicCurve2D.Float, Line2D.Float  Rects Interfaces: java.awt.Shape Classes: RectangularShape, RoundRectangle2D.Float, RoundRectangle2D, RoundRectangle2D.Double, Ellipse2D.Double, Rectangle2D, Ellipse2D, Ellipse2D.Float, Arc2D, Arc2D.Float, java.awt.Rectangle, Rectangle2D.Float, Rectangle2D.Double, Arc2D.Double

java.awt.geom.* Class Diagrams cont’d  Asym Interfaces: java.awt.Shape Classes: GeneralPath, Area, java.awt.Polygon  Point Classes: Point2D, Dimension2D, java.awt.Insets, java.awt.Dimension, java.awt.Point, Point2D.Float, Point2D.Double  Misc Interfaces: PathIterator Classes: AffineTransform, FlatteningPathIterator

java.awt.event.* Class Diagrams  Listener Interfaces: java.util.EventListener, AWTEventListener, ActionListener, KeyListener, AdjustmentListener, ComponentListener, MouseWheelListener, ContainerListener, MouseListener, FocusListener, MouseMotionListener, HierarchyBoundsListener, WindowStateListener, HierarchyListener, WindowFocusListener, InputMethodListener, WindowListener, ItemListener, TextListener Classes: java.util.EventListenerProxy, AWTEventListenerProxy, KeyAdapter, ComponentAdapter, ContainerAdapter, MouseAdapter, FocusAdapter, MouseMotionAdapter, HierarchyBoundsAdapter, WindowAdapter  Events Interfaces: java.awt.ActiveEvent Classes: InputMethodEvent, java.awt.AWTEvent, java.util.EventObject, HierarchyEvent, InvocationEvent, TextEvent, ActionEvent, ItemEvent, AdjustmentEvent, ComponentEvent, PaintEvent, FocusEvent, InputEvent, WindowEvent, ContainerEvent, MouseEvent, KeyEvent, MouseWheelEvent, java.awt.AWTKeyStroke, javax.swing.KeyStroke

java.awt.event.* Class Diagram cont’d  Support ventSupport.html Classes: java.awt.AWTEventMulticaster, java.awt.EventQueue

javax.swing.* Class Diagrams  Components  Hierarchy  JComponent  Labels  Slider+Progress  Spinner  CellEditor  CellRenderer  Container  RootpaneContainer  Panes  Scrolling  Layers Classes: javax.swing.JComponent

javax.swing.* Class Diagrams cont’d  Container  RootpaneContainer  Panes  Scrolling  Layers  Dialogs  JOptionPane  JFileChooser  JColorChooser

javax.swing.* Class Diagrams cont’d  Button+Menu  Buttons  ButtonModel  MenuSupport  MenuEvents  Lists  List+Combo  ListModel  ListEvent  Lists  List+Combo  ListModel  ListEvent

javax.swing.* Class Diagrams cont’d  Action  LookAndFeel  Utilities  Exceptions  javax.swing.border  javax.swing.event  Listener  Events  javax.swing.plaf  ComponentUI  UIResource  javax.swing.table  JTable  TableModel  Support  Events

javax.swing.* Class Diagrams cont’d  javax.swing.text  TextComponents  Formatter  Document  EditorKit  AttributeSet  View  Element  Position  Caret  AbstractWriter  Utilities  Events

javax.swing.* Class Diagrams cont’d  javax.swing.text.html  HTMLDocument  HTMLEditorKit  StyleSheet  Views  HTML  Parsing  javax.swing.text.html.parser  javax.swing.tree  JTree  TreeModel  TreeNode  Events  javax.swing.undo

General Approach to JAVA 2D API  Transition from the Graphics object to a Graphics2D object public void paintComponent(Graphics g) { super.paintComponent(g); // Typical Swing approach Graphics2D g2d = (Graphics2D)g; g2d.doSomeWork(...);... }  Create a Shape object Rectangle2D.Double rect =...; Ellipse2D.Double ellipse =...; Polygon poly =...; GeneralPath path =...; SomeShapeYouDefined shape =...; // Satisfies Shape interface...

General Approach to JAVA 2D API cont’d  Optional: modify drawing parameters g2d.setPaint (fillColorOrPattern); g2d.setStroke (penThicknessOrPattern); g2d.setComposite (someAlphaComposite); g2d.setFont(someFont); g2d.translate(...); g2d.rotate(...); g2d.scale(...); g2d.shear(...); g2d.setTransform(someAffineTransform);  Draw an outlined or solid version of the Shape g2d.draw(someShape); g2d.fill(someShape);

Example: Drawing Shapes import javax.swing.*; // For JPanel import java.awt.*; // For Graphics import java.awt.geom.*; // For Ellipse2D public class ShapeExample extends JPanel { private Ellipse2D.Double circle = new Ellipse2D.Double(10, 10, 350, 350); private Rectangle2D.Double square = new Rectangle2D.Double(10, 10, 350, 350); public void paintComponent(Graphics g) { clear(g); Graphics2D g2d = (Graphics2D) g; g2d.fill(circle); g2d.draw(square); } // super.paintComponent clears offscreen pixmap, we're using double buffering by default protected void clear (Graphics g) { super.paintComponent(g); } protected Ellipse2D.Double getCircle() { return(circle); } public static void main(String[] args) { WindowUtilities.openInJFrame(new ShapeExample(), 380, 400); } }

WindowUtilities.java Utility class that simplifies creating a window and setting the look and feel. import javax.swing.* ; import java.awt.*; public class WindowUtilities { /** Tell system to use native look and feel, as in previous * releases. Metal (Java) LAF is the default otherwise. **/ public static void setNativeLookAndFeel() { try { UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName()); } catch (Exception e) { System.out.println ("Error setting native LAF: " + e); } /** A simplified way to see a JPanel or other Container. * Pops up a JFrame with specified Container as the content pane. */ public static JFrame openInJFrame (Container content, int width, int height, String title, Color bgColor) { JFrame frame = new JFrame (title);

frame.setBackground (bgColor); content.setBackground (bgColor); frame.setSize (width, height); frame.setContentPane (content); frame.addWindowListener (new ExitListener()); frame.setVisible(true); return(frame); } /** Uses Color.white as the background color. public static JFrame openInJFrame(Container content, int width, int height, String title) { return(openInJFrame(content, width, height, title, Color.white)); } /** Uses Color. white as the background color, and the * name of the Container's class as the JFrame title. */ public static JFrame openInJFrame(Container content, int width, int height) { return(openInJFrame(content, width, height,content.getClass().getName(), Color.white)); } }

ExitListener.java A WindowListener with support to close the window import java.awt.*; import java.awt.event.*; public class ExitListener extends WindowAdapter { public void windowClosing (WindowEvent event) { System.exit(0); }

Paint attribute of the Graphics2D Filling a Shape  A Color (solid color): Color.red, Color.yellow  A GradientPaint (gradient fill gradually combining two colors) Constructors takes two points, two colors, and optionally a boolean flag that indicates that the color pattern should cycle.  A TexturePaint (tiled image), or  A new version of Paint that we write ourselves  Use setPaint and getPaint to change and retrieve the Paint settings.  setPaint and getPaint supersede the setColor and getColor methods in Graphics.

Example: Gradient Fills import java.awt.*; public class GradientPaintExample extends ShapeExample { // Red at (0,0), yellow at (175,175), changes gradually between. private GradientPaint gradient = new GradientPaint(0, 0, Color.red, 175, 175, Color.yellow, true); // true means to repeat pattern public void paintComponent(Graphics g) { clear(g); Graphics2D g2d = (Graphics2D)g; drawGradientCircle(g2d); } protected void drawGradientCircle (Graphics2D g2d) { g2d.setPaint(gradient); g2d.fill(getCircle()); g2d.setPaint(Color.black); g2d.draw(getCircle()); } public static void main(String[] args) { WindowUtilities.openInJFrame(new GradientPaintExample(), 380, 400); } }

Stroke Attributes Each of the shapes drawn by the applet is constructed from one of the geometries and is then rendered through Graphics2D. The rectHeight and rectWidth variables define the dimensions of the space where each shape is drawn, in pixels. The x and y variables change for each shape so that they are drawn in a grid formation. //draw Line2D.Double g2.draw (new Line2D.Double(x, y+rectHeight-1, x + rectWidth, y)); g2.drawString("Line2D", x, stringY); // draw Rectangle2D.Double g2.setStroke(stroke); g2.draw(new Rectangle2D.Double(x, y, rectWidth, rectHeight)); g2.drawString("Rectangle2D", x, stringY); // draw RoundRectangle2D.Double g2.setStroke(dashed); g2.draw(new RoundRectangle2D.Double(x, y, rectWidth, rectHeight, 10, 10) g2.drawString("RoundRectangle2D", x, stringY);

Stroke Attributes cont’d // draw Arc2D.Double g2.setStroke(wideStroke); g2.draw(new Arc2D.Double(x, y, rectWidth, rectHeight, 90, 135, Arc2D.OPEN)); // draw Ellipse2D.Double g2.setStroke(stroke); g2.draw (new Ellipse2D.Double(x, y, rectWidth, rectHeight));

Drawing GeneralPath (polygon) int x1Points[] = {x, x+rectWidth, x, x+rectWidth}; int y1Points[] = {y, y+rectHeight, y+rectHeight, y}; GeneralPath polygon = new GeneralPath(GeneralPath.WIND_EVEN_ODD, x1Points.length); polygon.moveTo(x1Points[0], y1Points[0]); for (int index = 1; index < x1Points.length; index++) { polygon.lineTo(x1Points[index], y1Points[index]); }; polygon.closePath(); g2.draw(polygon);

Drawing GeneralPath (polyline) int x2Points[] = {x, x+rectWidth, x, x+rectWidth}; int y2Points[] = {y, y+rectHeight, y+rectHeight, y}; GeneralPath polyline = new GeneralPath(GeneralPath.WIND_EVEN_ODD, x2Points.length); polyline.moveTo (x2Points[0], y2Points[0]); for (int index = 1; index < x2Points.length; index++) { polyline.lineTo(x2Points[index], y2Points[index]); }; g2.draw(polyline);

Stroke Attributes cont’d // fill Rectangle2D.Double (red) g2.setPaint(red); g2.fill(new Rectangle2D.Double(x, y, rectWidth,rectHeight)); // fill RoundRectangle2D.Double g2.setPaint(redtowhite); g2.fill(new RoundRectangle2D.Double(x, y, rectWidth, rectHeight, 10, 10)); // fill Arc2D g2.setPaint(red); g2.fill(new Arc2D.Double(x, y, rectWidth, rectHeight, 90, 135, Arc2D.OPEN));

Using the Java 2D APIs to define and render the Graphics and Text public class ShapesDemo2D extends JApplet { final static int maxCharHeight = 15; final static int minFontSize = 6; final static Color bg = Color.white; final static Color fg = Color.black; final static Color red = Color.red; final static Color white = Color.white; final static BasicStroke stroke = new BasicStroke(2.0f); final static BasicStroke wide Stroke = new BasicStroke(8.0f); final static float dash1[] = {10.0f} final static BasicStroke dashed = new BasicStroke(1.0f, BasicStroke.CAP_BUTT,BasicStroke.JOIN_MITER, 10.0f, dash1, 0.0f);

Dimension totalSize; FontMetrics fontMetrics; public void init() { //Initialize drawing colors setBackground(bg); setForeground(fg); } FontMetrics pickFont(Graphics2D g2, String longString, int xSpace) { boolean fontFits = false; Font font = g2.getFont(); FontMetrics fontMetrics = g2.getFontMetrics(); int size = font.getSize(); String name = font.getName(); int style = font.getStyle();

while ( !fontFits ) if ( (fontMetrics.getHeight() <= maxCharHeight) && (fontMetrics.stringWidth(longString) <= xSpace) ) { fontFits = true; } else { if ( size <= minFontSize ) { fontFits = true; } else { g2.setFont(font = new Font name, style, --size)); fontMetrics = g2.getFontMetrics(); } } } return fontMetrics; }

public void paint(Graphics g) { Graphics2D g2 = (Graphics2D) g; g2.setRenderingHint (RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON); Dimension d = getSize(); int gridWidth = d.width / 6; int gridHeight = d.height / 2; fontMetrics = pickFont(g2, "Filled and Stroked GeneralPath", gridWidth); Color fg3D = Color.lightGray; g2.setPaint(fg3D); g2.draw3DRect(0, 0, d.width - 1, d.height - 1, true); g2.draw3DRect(3, 3, d.width - 7, d.height - 7, false); g2.setPaint(fg); int x = 5; int y = 7; int rectWidth = gridWidth - 2*x; int stringY = gridHeight fontMetrics.getDescent(); int rectHeight = stringY - fontMetrics.getMaxAscent() - y - 2;