lecture18

# lecture18 - 1 Introduction to Computation and Problem...

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Unformatted text preview: 1 Introduction to Computation and Problem Solving Prof. Steven R. Lerman and Dr. V. Judson Harward Class 18: Class 18: Lab Lab Transformations in the 2D API Transformations in the 2D API 2 Affine Transformations • The 2D API provides strong support for affine transformations . – Affine means linear • An affine transformation maps 2D coordinates so that the straightness and parallelism of lines are preserved. • All affine transformations can be represented by a 3x3 floating point matrix. • There are a number of “primitive” affine transformations that can be combined: scaling, rotation, and translation. 1 3 Transformations in the 2D API • package. • its no argument constructor. • • – – – – • complex transformations. Transformations are represented by instances of the AffineTransform class in the java.awt.geom You can create a new AffineTransform object with AffineTransform at = new AffineTransform(); You can invoke any of the following methods on an AffineTransform object: at.scale(double sx, double sy) at.translate(double tx, double ty) at.rotate(double theta) at.rotate(double theta, double x, double y) These methods can be combined to build 4 Translation t y t x 1 1 1 x x y y + ⎡ ⎤ ⎡ ⎤ ⎡ ⎤ ⎢ ⎥ ⎢ ⎥ ⎢ ⎥ = + ⎢ ⎥ ⎢ ⎥ ⎢ ⎥ ⎢ ⎥ ⎢ ⎥ ⎢ ⎥ ⎣ ⎦ ⎣ ⎦ ⎣ ⎦ 1 1 t x x t t y y t 2 5 Translation Example, 1 } } } 6 Applying Transforms • Shapes baseXf.translate( 50, 50 ); Shape transformed = g2.fill(transformed); • g2.transform(baseXf); g2.fill(rect); import javax.swing.*; import java.awt.*; import java.awt.geom.*; public class TransformPanel extends JPanel { Rectangle2D.Double rect; public TransformPanel() { rect = new Rectangle2D.Double(0, 0, 50, 100); public void paintComponent(Graphics g) { Graphics2D g2 = (Graphics2D) g; g2.setPaint(Color.BLUE); AffineTransform baseXf = new AffineTransform(); // Shift to the right 50 pixels, down 50 pixels baseXf.translate(50,50); Shape s = baseXf.createTransformedShape( rect ); g2.fill(rect); You can apply a transformation to one or more and draw the result: AffineTransform baseXf = new AffineTransform(); rect = new Rectangle2D.Double(0, 0, 50, 100); baseXf.createTransformedShape( rect ); Or you can transform the coordinate space and everything in it: 3 7...
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## This note was uploaded on 11/29/2011 for the course CIVIL 1.00 taught by Professor Georgekocur during the Spring '05 term at MIT.

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lecture18 - 1 Introduction to Computation and Problem...

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