April 19th, 2016

Picture Lab – Activity 5

Classwork:
1. Open Picture.java and look for the method getPixels2D. Is it there?
2. Open SimplePicture.java and look for the method getPixels2D. Is it there?
3. Does the following code compile?
DigitalPicture p = new DigitalPicture();
4. Assuming that a no-argument constructor exists for SimplePicture, would the following
code compile?
DigitalPicture p = new SimplePicture();
5. Assuming that a no-argument constructor exists for Picture, does the following code
compile?
DigitalPicture p = new Picture();
6. Assuming that a no-argument constructor exists for Picture, does the following code
compile?
SimplePicture p = new Picture();
7. Assuming that a no-argument constructor exists for SimplePicture, does the following
code compile?
Picture p = new SimplePicture();

More Questions:
List nameList = new ArrayList();
Why wouldn’t you just declare nameList to be of the type ArrayList?

What do you think you will see if you modify the beach picture in the images folder to set all the blue values to zero?

Do you think you will still see a beach?

Exercises
1. Open PictureTester.java and run its main method. You should get the same results as running the main method in the Picture class. The PictureTester class contains class (static) methods for testing the methods that are in the Picture class.

2. Uncomment the appropriate test method in the main method of PictureTester to test any of the other methods in Picture.java. You can comment out the tests you don’t want to run. You can also add new test methods to PictureTester to test any methods you create in the Picture class.

Homework:
Exercises
3. Using the zeroBlue method as a starting point, write the method keepOnlyBlue that will keep only the blue values, that is, it will set the red and green values to zero. Create a class (static) method to test this new method in the class PictureTester. Be sure to call the new test method in the main method in PictureTester.

4. Write the negate method to negate all the pixels in a picture. To negate a picture, set the red value to 255 minus the current red value, the green value to 255 minus the current green value and the blue value to 255 minus the current blue value. Create a class (static) method to test this new method in the class PictureTester. Be sure to call the new test method in the main method in PictureTester.

5. Write the grayscale method to turn the picture into shades of gray. Set the red, green, and blue values to the average of the current red, green, and blue values (add all three values and divide by 3). Create a class (static) method to test this new method in the class PictureTester. Be sure to call the new test method in the main method in PictureTester.

6. Challenge — Explore the “water.jpg” picture in the images folder. Write a method fixUnderwater() to modify the pixel colors to make the fish easier to see. Create a class (static) method to test this new method in the class PictureTester. Be sure to call the new test method in the main method in PictureTester.