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Drawing in Java part 1
Drawing in Java part 1
Learning Goals
Learning Goals
Drawing on a Picture
Drawing on a Picture
Drawing Lines Exercise
Drawing Lines Exercise
Drawing Other Shapes
Drawing Other Shapes
AWT Graphics Class
AWT Graphics Class
Working with java
Working with java
Using Classes in Packages
Using Classes in Packages
Graphics Environment
Graphics Environment
Drawing Circles and Ellipses
Drawing Circles and Ellipses
Draw Circle Exercise
Draw Circle Exercise
Working with Fonts
Working with Fonts
To draw a string gObj
To draw a string gObj
Add a String to a Picture Exercise
Add a String to a Picture Exercise
Drawing Lines and Polygons
Drawing Lines and Polygons
Drawing Lines Exercise
Drawing Lines Exercise
Summary
Summary

Презентация: «Drawing in Java part». Автор: Barbara Jane Ericson. Файл: «Drawing in Java part.ppt». Размер zip-архива: 802 КБ.

Drawing in Java part

содержание презентации «Drawing in Java part.ppt»
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1 Drawing in Java part 1

Drawing in Java part 1

Barb Ericson Georgia Institute of Technology September 2006

Georgia Institute of Technology

2 Learning Goals

Learning Goals

Understand at a conceptual and practical level How to use the Turtle class to draw on a picture How to use the java.awt.Graphics class to do simple drawing How to draw simple shapes How to set the color How to set the font How to draw strings

Georgia Institute of Technology

3 Drawing on a Picture

Drawing on a Picture

What if we want to draw something on a picture? How about drawing a grid of lines on top of a picture? We could use a Turtle object to draw the lines Create the Turtle on a Picture object Picture p = new Picture(FileChooser.pickAFile()); Turtle turtle1 = new Turtle(p); Using the methods: moveTo(x,y), penUp(), penDown(), turnRight(), turnLeft(), turn(amount)

Georgia Institute of Technology

4 Drawing Lines Exercise

Drawing Lines Exercise

Write a method drawGrid in Picture.java to draw horizontal and vertical lines on the current picture, using a Turtle Draw 3 lines in x and 3 in y To test it: String file = FileChooser.getMediaPath(“barbara.jpg”); Picture p = new Picture(file); p.drawGrid(); p.show();

Georgia Institute of Technology

5 Drawing Other Shapes

Drawing Other Shapes

How would you draw a circle on a picture? How would you draw a string of characters? Java has a class that knows how to do these things Using a Graphics object It knows how to draw and fill simple shapes and images You can draw on a picture object By getting the graphics object from it pictureObj.getGraphics();

Georgia Institute of Technology

6 AWT Graphics Class

AWT Graphics Class

Methods of the Graphics class in the java.awt package let you paint Pick a color to use Draw some shapes Circles, Rectangles, Lines, Polygons, Arcs Shapes drawn on top of other shapes will cover them Set the font to use Draw some letters (strings)

Georgia Institute of Technology

7 Working with java

Working with java

awt.Color

To create a new color object new Color(redValue,greenValue,blueValue) There are predefined colors red, green, blue, black, yellow, gray, magenta, cyan, pink, orange To use these do: Color.RED or Color.red Set the current drawing color using graphicsObj.setColor(colorObj); Get the current drawing color using Color currColor = graphicsObj.getColor();

Georgia Institute of Technology

8 Using Classes in Packages

Using Classes in Packages

Java organizes classes into packages Groups of related classes The full name of a class is packageName.ClassName java.awt.Color If you want to use just the class name to refer to a class in a package Use the import statement before the class definition in your class import java.awt.Color; // to allow you to use Color or import java.awt.*; // to use any class in this package

Georgia Institute of Technology

9 Graphics Environment

Graphics Environment

0,0

+X

0, 0 is at the top left X increases to the right Y increases going down the page

+Y

400,200

Graphics are often positioned by their top left corner Coordinate units are measured in pixels

Georgia Institute of Technology

10 Drawing Circles and Ellipses

Drawing Circles and Ellipses

gObj.drawOval(x,y,width, height) gObj.fillOval(x,y,width, height) Give the x and y of the upper left corner of the enclosing rectangle Not a point on the circle or ellipse Give the width and height of the enclosing rectangle To make a circle use the same value for the width and height

x,y

height

width

Georgia Institute of Technology

11 Draw Circle Exercise

Draw Circle Exercise

Write a method to add a yellow sun to a picture Test with beach.jpg String file = FileChooser.getMediaPath(“beach.jpg”); Picture p = new Picture(file); p.drawSun(); p.show(); Save the new image with pictureObj.write(fileName);

Georgia Institute of Technology

12 Working with Fonts

Working with Fonts

Create a font object with the font name, style, and point size Font labelFont = new Font(“TimesRoman”, Font.BOLD, 24); Font normalFont = new Font(“Helvetica”,Font.PLAIN, 12); Set the current font gObj.setFont(labelFont); Get font information gObj.getStyle(), g.getSize(), g.getName(), g.getFamily

Georgia Institute of Technology

13 To draw a string gObj

To draw a string gObj

drawString(“test”,leftX,baselineY); Use FontMetrics class for drawing information FontMetrics currFontMetrics = g.getFontMetrics(); int baselineY = currFontMetrics.getHeight() - currFontMetrics.getDescent(); int width = currFontMetrics.stringWidth(“test”);

test string

Working with Strings

ascent

leading

leftX

height

baselineY

descent

Georgia Institute of Technology

14 Add a String to a Picture Exercise

Add a String to a Picture Exercise

Write a method drawString that will add some text to a picture Set the color to draw with Set the font to use when drawing the string Draw a string near the bottom left of the picture If you have time create another method that takes a string and y value and centers the string in x Test with String file = FileChooser.getMediaPath(“kitten2.jpg”); Picture p = new Picture(file); p.drawString(“Barbara Ericson”); p.show();

Georgia Institute of Technology

15 Drawing Lines and Polygons

Drawing Lines and Polygons

Line g.drawLine(x1,y1,x2,y2); Polygon Outlined Polygon gObj.drawPolygon(xArray,yArray,numPoints); gObj.drawPolygon(currPolygon); Filled Polygon gObj.fillPolygon(xArray, yArray, numPoints); gObj.fillPolygon(currPolygon);

x1,y1

x2,y2

Georgia Institute of Technology

16 Drawing Lines Exercise

Drawing Lines Exercise

Write a method (drawX) for adding two crossed lines to a picture Using a passed color Start one line at the top left corner of the picture End it at the bottom right corner of the picture Start the other line at the bottom left of the picture End it at the top right You can test it with barbara.jpg

Georgia Institute of Technology

17 Summary

Summary

You can draw using Turtle objects Or you can use java.awt.Graphics to do drawing Get the Graphics object from a Picture object Graphics graphics = pictureObj.getGraphics(); Set the color graphics.setColor(Color.RED); Do some simple drawing graphics.drawLine(x1,y1,x2,y2); graphics.drawOval(x1,y1,width,height); graphics.drawString(“string to draw”,leftX,baseline);

Georgia Institute of Technology

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