CS 180 Problem Solving and Object Oriented Programming Fall 2011

Transcription

1 CS 180 Problem Solving and Object Oriented Programming Fall 2011 hmp:// This Week: Notes for Week : Nov 21-25, /21 1. Review 2. Class BufferedImage 3. Pixel operaxons 4. Project 5 Aditya Mathur Department of Computer Science Purdue University West LafayeMe, IN, USA

2 Readings and Exercises for Week Readings: Chapter: 13.3, 13.4, 13.5;.3,.4 [Carry over from Week 13] Exercises: 13.11, 13.13

3 Revised Project Schedule Project 5: Assigned on Wednesday November 17. Deadline: Tuesday December 7. Special help sessions on: Dec 4, 5, 6, and 7 [To be announced] Special class: Sunday Dec 12, pm. LWSN 3102

4 Review: Thread interleaving, shared data, race, synchronizaxon

5 Interleaving There is usually no guarantee regarding the sequence in which statements in two or more threads will be executed. Write access to shared data may lead to unexpected results.

6 SynchronizaXon Use synchronized methods to allow sequenxal access to shared data that may be over wrimen by threads. No need to synchronize access to shared data that is read- only. In CS 180 we have only covered synchronized methods; other ways of synchronizaxon are also possible.

7 Project 5: Basics

8 Class BufferedImage import java.awt.image; // Declare im to be an object of type BufferedImage BufferedImage im;

9 A BufferedImage An array of pixels: pixel (0,0) int w=im.getwidth() int h=im.getheight() height (h) pixel (i, j) 0<=i<width 0<=j<height width (w) pixel (w,h)

10 A pixel A collecxon of RGB values in the default color model that we will use [R: Red, G: Green, B: Blue]. Each R, G, and B is an 8- bit integer with values ranging from 0 to 255. A combinaxon of values of R, G, and B gives a certain color to a pixel.

11 Reading a BufferedImage import java.awt.image; import javax.imageio.imageio; // Declare im to be an object of type BufferedImage // and read from a file BufferedImage im; try{ im=imageio.read(new File("Flower.jpg")); }catch(excepxon e){ System.out.println("File read unsuccessful"); }

12 Displaying a BufferedImage JLabel l=new JLabel(); // Create a label l.sethorizontalalignment(jlabel.center); // Set alignment; l.seticon(new ImageIcon(im));// Create and add an ImageIcon JFrame f=new JFrame( A Flower ); // Create a frame f.add(l, BorderLayout.CENTER); // Add label

13 ExtracXng RGB from a pixel // 1. Get RGB of pixel (i,j) int rgb=im.getrgb(i,j); // 2. Make a color object Color pixel=new Color(rgb); // 3. Extract colors from pixel int red=pixel.getred(); int green=pixel.getgreen(); int blue=pixel.getblue();

14 Modifying a pixel // 1. Make a Color object with red, green, and blue Color newpixel=new Color(red, green, blue); // 2. Get RGB of the new pixel int rgb=newpixel.getrgb(); // 3. Change pixel (i,j) of image im im.setrgb(i, j, rgb);

15 Image filtering: Removing colors x: color value from the image. R=x, G=0, B=0 R=0, G=0, B=x See a Java program to obtain the filtered images at the course Web site. R=0, G=x, B0 R, G, B denote the color components of RGB.

16 Project 5: The Program

17 Tasks Image mirroring Image reflecxon Image adjustment Pixel rotaxon Only one task performed at a Xme.

18 Image as an array of pixels 0 1 w- 1 0 x x x. x 1 x x x. x.. h- 1 x x x. x pixels

19 Threads, Image, and the Dispatcher Each thread reads its pixel, processes it, an writes it back w- 1 x x x. x x x x. x.. h- 1 x x x. x Th 1 Th 2 Th 3 Dispatcher Dispatcher gives a row or a column to a thread unxl the enxre image is processed.

20 SynchronizaXon What should be synchronized? Access to a pixel? Access to the image? Access to dispatcher?

21 Week : November 22-26, 2010 Hope you enjoyed this week! QuesXons? Contact your recitaxon instructor. Make full use of our office hours.