graphics in java part ii. lecture objectives learn how to use graphics in java

Graphics in JavaPart II

Lecture Objectives

• Learn how to use Graphics in Java

Lecture Objectives

• Outline:IntroductionGraphics Contexts and Graphics ObjectsColor ControlFont ControlDrawing Lines, Rectangles and OvalsDrawing ArcsDrawing Polygons and PolylinesThe Java2D APIJava2D Shapes

• 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)

Introduction

• 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

Graphics Context and Objects

• 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

Graphics Context and Objects (Cont’d)

• 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

Color Control

• 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

Color Control (Cont’d)

JColorChooser



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 );

Outline:

import

Class definition

define paint()


// 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();

}}

Outline:

define paint()

main() method

Program Output

Font Control

• Class Font Constructor takes three argumentspublic 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 );

• Methods getStyle() getSize() getName() getFamily() isPlain() isBold() isItalic() getFont() setFont(Font f)

Font Control (Cont’d)

• Class FontMetrics Has methods for getting font metrics g.getFontMetrics() - returns FontMetrics

object


Xy1

leading

ascent

baselinedescent

height

• FontMetrics (and Graphics) methods getAscent() getDescent() getLeading() getHeight() getFontMetrics() getFontMetrics( Font f )




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 );

Outline:

import

Class definition

define paint()


// 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(); }}

Outline:

define paint()

main() method

Program Output


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 );

Outline:

import

Class definition

define paint()


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(); }}

Outline:

define paint()

main() method

Program Output

• 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.

Drawing Lines, Rectangles and Ovals

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)


arc width

width

height

(x, y)

arc height

(x, y)

height

width

drawRoundRect() parameters

drawOval() parameters


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 );

Outline:

import

Class definition

define paint()


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(); }}

Outline:

define paint()

main() method

Program Output


• 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)

Drawing Arcs

Drawing Arcs (Cont’d)


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 );

Outline:

import

Class definition

define paint()

Drawing Arcs (Cont’d)

// 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(); }}

Outline:

define paint()

main() method

Program Output

• 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

Drawing Polygons and Polylines

• 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

Drawing Polygons and Polylines (Cont’d)


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 );

Outline:

Import

Class definition

define paint()


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(); }}

Outline:

define paint()

main() method

Program Output


• 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

Java2D API

• Sample methods from Graphics2D setPaint(paintObject)

•Paint object 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

Java2D Shapes

• 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

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()


• 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


• 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()


• Other methods rotate(radians) - rotate next shape around

origin translate(x, y) - translates origin to x, y


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 ) );

Outline:

import

Class definition

define paint()

Cast to Graphics2D


// 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


Code available on WebCT – Shapes2.javaOutline:

Program Output


graphics in java part ii. lecture objectives learn how to use graphics in java

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