Problem Solving Assignment 4

Due: Tuesday, Jan 27, 11:59 pm

• You will be solving this homework as a pair-programming team.
• Besides writing the code there is an interview process required for this PSA (details at bottom after turn-in instructions.)
  
• This homework requires skills from Chapters 2, 3, and 4.

• Make a directory in your HOME DIRECTORY(called PSA4). (You only do this on ONE partner's account)
• Copy the bookClasses folder into the PSA4 directory.
• When you work in Dr. Java BE SURE you are opening and saving files in the PSA4/bookClasses directory.

There are two problems in this PSA:

1. Color Subtraction -- Write a program that subtracts the red, blue, and green components of all pixels of a Picture by specified values. To do this, you will write one method in Picture.java and a main program to test your method by showing and exploring the original and changed picutres.
2. Tri-Effect -- Write a program that modifies a Picture so that the top 1/3rd of the picture is the negative of the picture, the middle 1/3rd is grayscale, and the bottom 1/3rd of the picture is any effect of your choice. To do this, you will write and call three methods in Picture.java. In addition, you will post the resulting image from this problem on the class wiki.

Details

You must put a comment at the top of your code that specifies, for both you and your partner, your: real names, login names, and PIDs, AND a two to four sentence description of the program (one description for each program).

Use a multi-line comment (/* */).

You must observe an 80 column limit. No line of your program may be longer than the 80th column on the screen.

Color Subtraction

• Add a method to Picture.java called subtractColor (be sure to use PSA4/bookClasses/Picture.java). Your method takes three parameters -- which specify how much the color components of all pixels of the picture should be reduced. For example, if you pass (100, 20, 45) as parameters to your method and the color values of one of the pixels of the picture is (150, 200, 50), then these color values should be reduced to (50, 180, 5) after your method is called. Note that a negative color value is automatically counted as 0. The order in which the color values are passed to the method should be red, blue, and green.
• The method should reduce the color values of ALL the pixels in the picture.

Testing your methods (in an application):

• Create a new file PSA4A.java (you can start with this template here). Save the file in PSA4/bookClasses.
• Fill in the statements (inside the main method) you need to test and show the results of your methods:
  • Use the FileChooser.pickAFile() command to pick a picture (you can pick a picture in your mediasources directory -- or better yet -- use one of your own!).
  • BEFORE you modify this picture, we want to make a COPY of it (so we can "see" the difference after it is changed. Do this with the same technique used in lab. Make another new Picture that is a copy of the one you just made. Use the constructor that has you do Picture copy = new Picture(original);
  • Next show and explore the original picture you picked.
  • Note that you can explore a picture by calling the predefined explore() method on that picture.
  • Then call your method to change the COPY of the picture you made.
  • Then show and explore the copy of the picture after you called your method on it to change it.
  • Mouse around to explore the original and changed picture to make sure your method works correctly (that is a specific pixel in the original picture has been reduced by the right amounts in its red, green, and blue components for the copied picture).
  Though not required for a point -- hey play around!!! What COOL pictures can you make? Use yout own photos! Post them on the wiki!

Tri-Effect

• Add a method (negative) to Picture.java that takes in two parameters, the first and last index which represent the region (part) of the pixel array to be modified.
  • The method should access the pixel array of the calling picture object (that is use the this.getPixels() line to store the picture's pixels in an array).
  • Then, using a while loop, invert the color (create the negative) of each pixel between (and including) the provided indices.

• Add another method to Picture.java named grayscale similar to the negative method called grayscale which also takes the first and last index in the pixel array to be modified. For those pixels in range, you need to change the colors to their appropriate grayscale color using another while loop.

• Add another method to Picture.java, similar to the the negative and grayscale methods which also takes the first and last index in the pixel array to be modified. Apply any effect of your choice to the pixels in range using a while loop. BE CREATIVE!!!

• Create a new file PSA4B.java (you can start with this template here).
• This file will load a Picture of your choice (either a bookClasses image or a personal image) using FileChooser.pickAFile().
• Display the original image.
• Then call the negative method on the first 1/3 of pixels in the image. Next call the grayscale method on the middle 1/3 of pixels in the image. Then apply the myFilter method to the bottom 1/3 of the pixels in the image.
• Lastly, display your new image.

How to turnin your homework electronically

When you are ready to turn in your homework, first open a terminal window by right clicking on the empty area of your computer's desktop (have to use lab computers or remotely connect from your home computer using SSH or Putty) and select "Open a New Terminal". Then, run bundlePSA4 from your PSA4/bookClasses directory. 3 files are required to be submitted for PSA4:

• Picture.java
• PSA4A.java
• PSA4B.java

-bash-2.05b$  cd ~/PSA4/bookClasses 
-bash-2.05b$  bundlePSA4 
Good; all required files are present:

        Picture.java
        PSA4A.java
        PSA4B.java

Do you want to go ahead and turnin these files? [y/n] y
OK.  Proceeding.


Performing turnin of approx. XXXX bytes 
Copying to /home/linux/ieng6/cs8f/turnin.dest/cs8wxx.PSA4
.
Done.
Total bytes written: XXXX 
Please check to be sure that's reasonable.
Turnin successful.

Make sure the Turnin is successful, otherwise we won't receive your submission! . If you want to make changes after you've turned in your homework, make the changes and run bundlePSA2 again. The program will warn you that a "previously turned-in file exists" and ask if "you wish to over-write this existing file". Respond in the affirmative by typing y and pressing the Enter key.

Getting your interview done INDIVIDUALLY

10% of your grade on this assignment will come from an interview you will have with one of the tutors during Open Lab Hours. You have 48 weekday hours after the electronic turnin deadline to get your interview done. The deadline for the interview for PSA4 is Thurs Jan 29 (theoretically at midnight, but actually by the end of the last tutor hour scheduled). Remember, the tutors may be busy after 4pm helping CSE8B students

You get an interview by going into B260 during a scheduled tutor hour. Find the tutor, ask them if you can interview for the 8A PSA. If they have others who are waiting for interviews, your name will go on the end of the list of people waiting. Interviews take about 5 minutes each. It is your responsibility to go in early enough that you can get your interview completed. If everyone waits until the last hour on Thurs, this will not work.

For the interview you will need to have a copy of your team's assignment in your account. If you are using your partner's account to submit the files, make sure you email them to yourself and save them under your account so that you have them available for the interview. The tutor will ask you to log in, change to the directory where your work is and then to follow their directions. They will ask you to run your program to show that it works, open files in Dr. Java (or your favorite editor), and ask you questions about HOW your code works. Additionally, they may question you as to how you would (theoretically) make small changes to the program to have it do something slightly different. You will not actually be required to change your code.

Learning to be able to explain your problem solving process and discuss code with another human being is a very important professional skill. We hope that this process will help you develop this skill.