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Graphics in Java Part II

Graphics in Java Part II. Lecture Objectives. Learn how to use Graphics in Java. Lecture Objectives. Outline: Introduction Graphics Contexts and Graphics Objects Color Control Font Control Drawing Lines, Rectangles and Ovals Drawing Arcs Drawing Polygons and Polylines

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Graphics in Java Part II

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  1. Graphics in JavaPart II

  2. Lecture Objectives • Learn how to use Graphics in Java

  3. Lecture Objectives • Outline: Introduction Graphics Contexts and Graphics Objects Color Control Font Control Drawing Lines, Rectangles and Ovals Drawing Arcs Drawing Polygons and Polylines The Java2D API Java2D Shapes

  4. Introduction • In this lecture, we will learn about: • Drawing 2D shapes. • Using colors. • Using fonts. • Java Graphics Support: • Has a class hierarchy for its graphics classes and 2D API classes • Java Coordinate System: • (x, y) pairs • x - horizontal axis • y - vertical axis • Upper left corner is (0,0) • Coordinates measured in Pixels (Picture Element - Smallest unit of resolution)

  5. Graphics Context and Objects • Graphics context • Enables drawing on screen • Graphics object manages graphics context • Controls how information is drawn • Has methods for drawing, font manipulation, etc • Graphics an abstract class! • Cannot instantiate objects • Implementation hidden - more portable • Class Component • Superclass for many classes in java.awt package • Method paint() takes Graphics object as argument

  6. Graphics Context and Objects (Cont’d) • Class Component (Cont’d) • paint() often called in response to an event • repaint() calls update(), which forces a paint() operation • update() rarely called directly! • Sometimes overridden to reduce "flicker" Headers: public void repaint() public void update( Graphics g ) • In this lecture: • Focus on paint() method

  7. Color Control • Class Color • Defines methods and constants for manipulating colors • Colors created from red, green, and blue (RGB) components • RGB value: 3 integers from 0 to 255 each, or three floating point values from 0 to 1.0 each • Larger the value, more of that color • Color methods getRed(), getGreen(), getBlue() return an integer between 0 and 255 representing amount • Graphics method setColor() sets drawing color • Takes Color object • Method getColor() gets current color setting

  8. Color Control (Cont’d) • Component JColorChooser • Displays dialog allowing user to select a color • Method showDialog() • First argument: reference to parent Component (window from which dialog being displayed) • Modal dialog - user cannot interact with other dialogs while active • Second argument: String for title bar • Third argument: Initial selected color • Returns a Color object • Class Container • Method setBackground() - takes Color object • Sets background color

  9. Color Control (Cont’d) JColorChooser

  10. Color Control (Cont’d) • Outline: • import • Class definition • define paint() import java.awt.*; import javax.swing.*; import java.awt.event.*; public class ShowColors extends Jframe { public ShowColors() { super( "Using colors" ); setSize( 400, 130 ); show(); } public void paint( Graphics g ) { // set new drawing color using integers g.setColor( new Color( 255, 0, 0 ) ); g.fillRect( 25, 25, 100, 20 ); g.drawString( "Current RGB: " + g.getColor(), 130, 40 ); // set new drawing color using floats g.setColor( new Color( 0.0f, 1.0f, 0.0f ) ); g.fillRect( 25, 50, 100, 20 ); g.drawString( "Current RGB: " + g.getColor(), 130, 65 );

  11. Color Control (Cont’d) Outline: define paint() main() method Program Output // set new drawing color using static Color objects g.setColor( Color.blue ); g.fillRect( 25, 75, 100, 20 ); g.drawString( "Current RGB: " + g.getColor(), 130, 90 ); // display individual RGB values Color c = Color.magenta; g.setColor( c ); g.fillRect( 25, 100, 100, 20 ); g.drawString( "RGB values: " + c.getRed() + ", " + c.getGreen() + ", " + c.getBlue(), 130, 115 ); } public static void main( String args[] ) { ShowColors app = new ShowColors(); } }

  12. Font Control • Class Font • Constructor takes three arguments • public Font( String name, int style, int size) • name: any font supported by system (Serif, Monospaced) • style: constants FONT.PLAIN, FONT.ITALIC, FONT.BOLD • Combinations: FONT.ITALIC + FONT.BOLD • size: measured in points (1/72 of an inch) • Use similar to Color • g.setFont( fontObject );

  13. Font Control (Cont’d) • Methods • getStyle() • getSize() • getName() • getFamily() • isPlain() • isBold() • isItalic() • getFont() • setFont(Font f)

  14. Font Control (Cont’d) • Class FontMetrics • Has methods for getting font metrics • g.getFontMetrics() - returns FontMetrics object leading Xy1 height ascent baseline descent

  15. Font Control (Cont’d) • FontMetrics (and Graphics) methods • getAscent() • getDescent() • getLeading() • getHeight() • getFontMetrics() • getFontMetrics( Font f )

  16. Font Control (Cont’d) • Outline: • import • Class definition • define paint() import java.awt.*; import javax.swing.*; import java.awt.event.*; public class Fonts extends Jframe { public Fonts() { super( "Using fonts" ); setSize( 420, 125 ); show(); } public void paint( Graphics g ) { // set current font to Serif (Times), bold, 12pt // and draw a string g.setFont( new Font( "Serif", Font.BOLD, 12 ) ); g.drawString( "Serif 12 point bold.", 20, 50 ); // set current font to Monospaced (Courier), // italic, 24pt and draw a string g.setFont( new Font( "Monospaced", Font.ITALIC, 24 ) ); g.drawString( "Monospaced 24 point italic.", 20, 70 );

  17. Font Control (Cont’d) Outline: define paint() main() method Program Output // set current font to SansSerif (Helvetica), // plain, 14pt and draw a string g.setFont( new Font( "SansSerif", Font.PLAIN, 14 ) ); g.drawString( "SansSerif 14 point plain.", 20, 90 ); // set current font to Serif (times), bold/italic, // 18pt and draw a string g.setColor( Color.red ); g.setFont(new Font( "Serif", Font.BOLD + Font.ITALIC, 18 ) ); g.drawString( g.getFont().getName() + " " + g.getFont().getSize() + " point bold italic.", 20, 110 ); } public static void main( String args[] ) { Fonts app = new Fonts(); } }

  18. Font Control (Cont’d) • Outline: • import • Class definition • define paint() import java.awt.*; import java.awt.event.*; import javax.swing.*; public class Metrics extends JFrame { public Metrics() { super( "Demonstrating FontMetrics" ); setSize( 510, 210 ); show(); } public void paint( Graphics g ) { g.setFont( new Font( "SansSerif", Font.BOLD, 12 ) ); FontMetrics fm = g.getFontMetrics(); g.drawString( "Current font: " + g.getFont(), 10, 40 ); g.drawString( "Ascent: " + fm.getAscent(), 10, 55 ); g.drawString( "Descent: " + fm.getDescent(), 10, 70 ); g.drawString( "Height: " + fm.getHeight(), 10, 85 ); g.drawString( "Leading: " + fm.getLeading(), 10, 100 );

  19. Font Control (Cont’d) Outline: define paint() main() method Program Output Font font = new Font( "Serif", Font.ITALIC, 14 ); fm = g.getFontMetrics( font ); g.setFont( font ); g.drawString( "Current font: " + font, 10, 130 ); g.drawString( "Ascent: " + fm.getAscent(), 10, 145 ); g.drawString( "Descent: " + fm.getDescent(), 10, 160 ); g.drawString( "Height: " + fm.getHeight(), 10, 175 ); g.drawString( "Leading: " + fm.getLeading(), 10, 190 ); } public static void main( String args[] ) { Metrics app = new Metrics(); } }

  20. Drawing Lines, Rectangles and Ovals • Graphics methods for drawing shapes: • drawLine(x1, y1, x2, y2) • Line from x1, y1 to x2, y2 • drawRect(x1, y1, width, height) • Draws rectangle with upper left corner x1, y1 • fillRect(x1, y1, width, height) • As above, except fills rectangle with current color • clearRect(x1, y1, width, height) • As above, except fills rectangle with background color • draw3DRect(x1, y1, width, height, isRaised) • Draws 3D rectangle, raised if isRaised is true, else lowered.

  21. Drawing Lines, Rectangles and Ovals (Cont’d) • Graphics methods for drawing shapes (Cont’d) • fill3DRect • As previous, but fills rectangle with current color • drawRoundRect(x, y, width, height, arcWidth, arcHeight) • Draws rectangle with rounded corners. See diagram next slide. • fillRoundRect(x, y, width, height, arcWidth, arcHeight) • drawOvalx, y, width, height) • Draws oval in bounding rectangle (see diagram) • Touches rectangle at midpoint of each side • fillOval(x, y, width, height)

  22. Drawing Lines, Rectangles and Ovals (Cont’d) (x, y) drawRoundRect() parameters arc height arc width height width (x, y) drawOval() parameters height width

  23. Drawing Lines, Rectangles and Ovals (Cont’d) • Outline: • import • Class definition • define paint() import java.awt.*; import java.awt.event.*; import javax.swing.*; public class LinesRectsOvals extends JFrame { private String s = "Using drawString!"; public LinesRectsOvals() { super( "Drawing lines, rectangles and ovals" ); setSize( 400, 165 ); show(); } public void paint( Graphics g ) { g.setColor( Color.red ); g.drawLine( 5, 30, 350, 30 ); g.setColor( Color.blue ); g.drawRect( 5, 40, 90, 55 ); g.fillRect( 100, 40, 90, 55 ); g.setColor( Color.cyan ); g.fillRoundRect( 195, 40, 90, 55, 50, 50 ); g.drawRoundRect( 290, 40, 90, 55, 20, 20 );

  24. Drawing Lines, Rectangles and Ovals (Cont’d) Outline: define paint() main() method Program Output g.setColor( Color.yellow ); g.draw3DRect( 5, 100, 90, 55, true ); g.fill3DRect( 100, 100, 90, 55, false ); g.setColor( Color.magenta ); g.drawOval( 195, 100, 90, 55 ); g.fillOval( 290, 100, 90, 55 ); } public static void main( String args[] ) { LinesRectsOvals app = new LinesRectsOvals(); } }

  25. Drawing Arcs • Arc • Portion of an oval • Measured in degrees • Starts at a starting angle and sweeps the number of degrees specified by arc angle • Positive - counterclockwise • Negative - clockwise • When drawing an arc, specify bounding rectangle for an oval • drawArc(x, y, width, height, startAngle, arcAngle) • fillArc - as above, but draws a solid arc (sector)

  26. Drawing Arcs(Cont’d) • Outline: • import • Class definition • define paint() import java.awt.*; import javax.swing.*; import java.awt.event.*; public class DrawArcs extends Jframe { public DrawArcs() { super( "Drawing Arcs" ); setSize( 300, 170 ); show(); } public void paint( Graphics g ) { // start at 0 and sweep 360 degrees g.setColor( Color.yellow ); g.drawRect( 15, 35, 80, 80 ); g.setColor( Color.black ); g.drawArc( 15, 35, 80, 80, 0, 360 ); // start at 0 and sweep 110 degrees g.setColor( Color.yellow ); g.drawRect( 100, 35, 80, 80 ); g.setColor( Color.black ); g.drawArc( 100, 35, 80, 80, 0, 110 );

  27. Drawing Arcs(Cont’d) Outline: define paint() main() method Program Output // start at 0 and sweep -270 degrees g.setColor( Color.yellow ); g.drawRect( 185, 35, 80, 80 ); g.setColor( Color.black ); g.drawArc( 185, 35, 80, 80, 0, -270 ); // start at 0 and sweep 360 degrees g.fillArc( 15, 120, 80, 40, 0, 360 ); // start at 270 and sweep -90 degrees g.fillArc( 100, 120, 80, 40, 270, -90 ); // start at 0 and sweep -270 degrees g.fillArc( 185, 120, 80, 40, 0, -270 ); } public static void main( String args[] ) { DrawArcs app = new DrawArcs(); } }

  28. Drawing Polygons and Polylines • Polygon - multisided shape • Polyline - series of connected points • Methods of class Polygon • drawPolygon(xPoints[], yPoints[], points) • Draws a polygon, with x and y points specified in arrays. Last argument specifies number of points • Closed polygon, even if last point different from first • drawPolyline(xPoints[], yPoints, points) • As above, but draws a polyline • Open polyline

  29. Drawing Polygons and Polylines (Cont’d) • Methods of class Polygon • drawPolygon(myPolygon) • Draws specified closed polygon • fillPolygon(xPoints[], yPoints[], points) • Draws a solid polygon • fillPolygon(myPolygon) • Draws specified solid polygon • Polygon(xValues[], yValues[], numberOfPoints) • Constructs a new polygon object • myPolygon.addPoint(x, y) • Add pairs of x-y coordinates to polygon object

  30. Drawing Polygons and Polylines (Cont’d) • Outline: • Import • Class definition • define paint() import java.awt.*; import java.awt.event.*; import javax.swing.*; public class DrawPolygons extends Jframe { public DrawPolygons() { super( "Drawing Polygons" ); setSize( 275, 230 ); show(); } public void paint( Graphics g ) { int xValues[] = { 20, 40, 50, 30, 20, 15 }; int yValues[] = { 50, 50, 60, 80, 80, 60 }; Polygon poly1 = new Polygon( xValues, yValues, 6 ); g.drawPolygon( poly1 ); int xValues2[] = { 70, 90, 100, 80, 70, 65, 60 }; int yValues2[] = { 100, 100, 110, 110, 130, 110, 90 }; g.drawPolyline( xValues2, yValues2, 7 ); int xValues3[] = { 120, 140, 150, 190 }; int yValues3[] = { 40, 70, 80, 60 }; g.fillPolygon( xValues3, yValues3, 4 );

  31. Drawing Polygons and Polylines (Cont’d) Outline: define paint() main() method Program Output Polygon poly2 = new Polygon(); poly2.addPoint( 165, 135 ); poly2.addPoint( 175, 150 ); poly2.addPoint( 270, 200 ); poly2.addPoint( 200, 220 ); poly2.addPoint( 130, 180 ); g.fillPolygon( poly2 ); } public static void main( String args[] ) { DrawPolygons app = new DrawPolygons(); } }

  32. Java2D API • Java2D API • Advanced two dimensional graphics capabilities • Too many capabilities to cover (for overview, see demo) • Drawing with Java2D API • Use instance of class Graphics2D (package java.awt) • Subclass of Graphics • Has all graphics capabilities we have previously discussed • Must downcast Graphics reference passed to paint Graphics2D g2d = (Graphics2D) g; • This technique used in programs of next section

  33. Java2D Shapes • Sample methods from Graphics2D • setPaint(paintObject) • Paintobject is an object of a class that implements java.awt.Paint • Can be an object of class Color, GradientPaint, SystemColor, TexturePaint • GradientPaint(x1, y1, color1, x2, y2, color2, cyclic) • Creates a gradient (slowly changing color) from x1, y1, to x2, y2, starting with color1 and changing to color2 • If cyclic true, then cyclic gradient (keeps transitioning colors) • If acyclic, only transitions colors once

  34. Java2D Shapes (Cont’d) • Sample methods from Graphics2D • fill ( shapeObject ) • Draws a filled Shape object • Instance of any class that implements Shape (java.awt) • Ellipse2D.Double, Rectangle2D.Double • Double-precision inner classes of Ellipse2D • setStroke( strokeObject ) • Set a shape's borders • Instance of a class that implements Stroke (java.awt) • BasicStroke( width ) - One of many constructors • This constructor specifies width in pixels of border

  35. Java2D Shapes (Cont’d) • Sample methods from Graphics2D • draw (shapeObject) • Draws specified Shape object • Class BufferedImage • Can produce images in color or grayscale • Can create patterns by drawing into the BufferedImage object • Class TexturePaint • Constructor can take BufferedImage and shape to fill • Object of class TexturePaint then drawn using setPaint()

  36. Java2D Shapes (Cont’d) • Class Arc2D.Double • Similar to normal arcs, except has another argument at end • Arc2D.PIE - close arc with two lines • Arc2D.CHORD - draws line from endpoints of arc • Arc2D.OPEN - arc not closed • Class BasicStroke • Can be used to create customized dashed lines, set how lines end and join

  37. Java2D Shapes (Cont’d) • Class GeneralPath • A general path is a shape made from lines and curves • Method moveTo() • Specifies first point in a general path • Method lineTo() • Draws a line to next point in general path • Method closePath() • Draws line from last point to point specified in last call to moveTo()

  38. Java2D Shapes (Cont’d) • Other methods • rotate(radians) - rotate next shape around origin • translate(x, y) - translates origin to x, y

  39. Java2D Shapes (Cont’d) • Outline: • import • Class definition • define paint() • Cast to Graphics2D import javax.swing.*; import java.awt.event.*; import java.awt.*; import java.awt.geom.*; import java.awt.image.*; public class Shapes extends Jframe { public Shapes() { super( "Drawing 2D shapes" ); setSize( 425, 160 ); show(); } public void paint( Graphics g ) { // create 2D by casting g to Graphics2D Graphics2D g2d = ( Graphics2D ) g; // draw 2D ellipse filled with a blue-yellow gradient g2d.setPaint( new GradientPaint( 5, 30, // x1, y1 Color.blue, // initial Color 35, 100, // x2, y2 Color.yellow, // end Color true ) ); // cyclic g2d.fill( new Ellipse2D.Double( 5, 30, 65, 100 ) );

  40. Java2D Shapes (Cont’d) // draw 2D rectangle in red g2d.setPaint( Color.red ); g2d.setStroke( new BasicStroke( 10.0f ) ); g2d.draw(new Rectangle2D.Double( 80, 30, 65, 100 ) ); // draw 2D rounded rectangle with a buffered background BufferedImage buffImage = new BufferedImage(10, 10, BufferedImage.TYPE_INT_RGB ); Graphics2D gg = buffImage.createGraphics(); gg.setColor( Color.yellow ); // draw in yellow gg.fillRect( 0, 0, 10, 10 ); // draw a filled rectangle gg.setColor( Color.black ); // draw in black gg.drawRect( 1, 1, 6, 6 ); // draw a rectangle gg.setColor( Color.blue ); // draw in blue gg.fillRect( 1, 1, 3, 3 ); // draw a filled rectangle gg.setColor( Color.red ); // draw in red gg.fillRect( 4, 4, 3, 3 ); // draw a filled rectangle // paint buffImage onto the JFrame g2d.setPaint(new TexturePaint(buffImage, new Rectangle( 10, 10 ) ) ); g2d.fill(new RoundRectangle2D.Double(155, 30, 75, 100, 50, 50 ) ); // draw 2D pie-shaped arc in white g2d.setPaint( Color.white ); g2d.setStroke( new BasicStroke( 6.0f ) ); g2d.draw(new Arc2D.Double(240, 30, 75, 100, 0, 270, Arc2D.PIE ) ); Outline: paint() Program Output

  41. Java2D Shapes (Cont’d) Code available on WebCT – Shapes2.java Outline: Program Output

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