Description
1 Introduction
Hello everyone! This week, we will be working with classes we provide to construct your very own
class, as well as getting some nice 2D array practice. Behold your next assignment: the Picture
Befuddler!
2 Problem Description
So here’s the scoop. You’re a museum thief — but not just any museum thief. You are a museum
thief with a sense of humor. Your master plan to confuse the police investigators is to leave multiple
fake copies of the art that youve stolen behind in your wake. But to make things even more
interesting (or perhaps frustrating for your chasers), youve modified all of the fake copies to be
silly alterations based on the original picture, some of which are barely recognizable. You must
use your knowledge of programming and RGB pixels to create simple image filters. Here are the
following ways you can choose to alter copies of your stolen picture:
1. greyscale(): Requires that you take the average of the RGB (red, green, and blue!) color
channels for each pixel and then set each of the channels to that averaged value.
2. invert(): Subtract each of the RGB channel values from the maximum possible value allowed
(255) and then set each channel to its respective difference.
3. noRed(): Remove the red component from each pixel so only the blue and green components
are affecting the image.
4. blackAndWhite(): Like greyscale, take the average of the RGB values for each pixel. If the
average for the pixel is above 127, set that pixel to white (255, 255, 255). If it is below, set
it to black (0, 0, 0).
5. maximize(): For each pixel, find the component with the highest value. Set the remaining
two values to zero. If two are tied for highest, set the third to zero; if all three are tied for
highest, leave it as is.
1
6. overlay(Pic other): This alteration takes in another picture and overlays the two pictures
over each other, starting at the top left corner of both images.1 To accomplish this, average
the R, G, and B values for both images. Think carefully about which pixels you are going to
loop through, as in this method you will need the pixel values of not one but two different
images!
3 Solution Description
Create a class called ImageProcessor that implements all of these methods. Some things to note
about ImageProcessor: You must have a constructor for ImageProcessor that takes in a Pic object
as its parameter. Any additional constructors are up to you.
• Use the given Pixel and Pic classes to write ImageProcessor; thus, ImageProcessor is manipulating a picture of type Pic which contains a two-dimensional array of Pixel objects.
• When instantiating an ImageProcessor, you should set some Pic instance variable of ImageProcessor to be the clean, unmodified image. All of the manipulation methods will use
this unmodified image as the base image.
• In the modification methods, do not modify the original picture! Instead, create a temporary copy of that picture which you will then modify using the methods of the Pic and Pixel
classes. This allows you to call the manipulation methods one after the other without worrying about them stacking on top of each other.
• Each modification method should then return the modified Pic. These methods should be
instance methods (that is, non-static methods).
• Finally, write a main method that instantiates an ImageProcessor using an image name
passed in through the command-line arguments. Then, call each of your manipulation methods on that object and show the returned picture. If the user provides a second command line
argument, call overlay() using that second argument. Yes, this means your program should
open 6 different windows when it is run.
4 Example Output
Using our provided picture, here is some example output for greyscale, invert, noRed, blackAndWhite, maximize, and watermark, respectively:
1
In the case where the second image is larger than the first, you should ignore the parts that do not overlap. The
final overlay dimensions should be the same as the original image.
2
3
4
5
5 Tips
First, make sure you understand how RGB pixel color values work. Essentially, each pixel has a
value 0 and 255 for the Red, Blue, and Green intensities, respectively. All colors are made up as
varying amounts of these values. Do not worry about the alpha value for this assignment (though
you are free to play around with it if you would like).
• Think about how you might iterate through a 2D array to find all of the pixels. It takes one
loop to find all the elements within a 1D array. How many might it take to do the same for a
2D array?
• How might you get the color channels of every pixel? Make sure you read the methods in
both Pic and Pixel, you will need to use the methods in these classes to implement ImageProcessor.
• Since you are making copies of the picture youre manipulating, you will have to make sure
you can return that copy. Be sure to read the Pic class to see if there are any way you can
copy a Pic object.
• You are not to modify Pic.java or Pixel.java. You are given every method required to do
this assignment already. Your submissions will be run with the unmodified Pic.java and
Pixel.java, so if your program is relying on changes youve made then your grade will suffer.
6 Checkstyle
Review the Style Guide and download the Checkstyle jar and associated XML file. Run Checkstyle
on your code like so:
$ java -jar checkstyle-5.6-all.jar -c cs1331-checkstyle.xml *.java
Starting audit…
Audit done.
The message above means there were no Checkstyle errors. You can easily count Checkstyle errors
by piping the output of Checkstyle through wc -l and subtracting 2 for the two non-error lines
printed above (which is how we will deduct points). For example:
$ java -jar checkstyle-5.6-all.jar -c cs1331-checkstyle.xml *.java | wc -l
2
Food for thought: is there a one-liner like above that shows you only the number of
errors? Hint: man grep.
Alternatively, if you are on Windows, you can use the following instead:
6
C:\> java -jar checkstyle-5.6-all.jar -c cs1331-checkstyle.xml *.java | findstr /v “Starting
audit…” | findstr /v “Audit done” | find /c /v “hascode()”
0
The Java source files we provide contain no Checkstyle errors. For this assignment, there will be
a maximum of 10 points lost due to Checkstyle errors (1 point per error). In future homeworks we
will be increasing this cap, so get into the habit of fixing these style errors early!
7 Turn-in Procedure
Submit all of the Java source files you created to T-Square. Do not submit any compiled bytecode
(.class files), the Checkstyle jar file, the cs1331-checkstyle.xml file, or any .java
files we have provided you. When you’re ready, double-check that you have submitted and not just
saved a draft.
8 Verify the Success of Your Submission to T-Square
Practice safe submission! Verify that your HW files were truly submitted correctly, the upload
was successful, and that the files compile and run. It is solely your responsibility to turn in your
homework and practice this safe submission safeguard.
1. After uploading the files to T-Square you should receive an email from T-Square listing the
names of the files that were uploaded and received. If you do not get the confirmation email
almost immediately, something is wrong with your HW submission and/or your email. Even
receiving the email does not guarantee that you turned in exactly what you intended.
2. After submitting the files to T-Square, return to the Assignment menu option and this homework. It should show the submitted files.
3. Download copies of your submitted files from the T-Square Assignment page placing them
in a new folder.
4. Recompile and test those exact files.
5. This helps guard against a few things.
(a) It helps insure that you turn in the correct files.
(b) It helps you realize if you omit a file or files.2
(If you do discover that you omitted a
file, submit all of your files again, not just the missing one.)
(c) Helps find last minute causes of files not compiling and/or running.
2Missing files will not be given any credit, and non-compiling homework solutions will receive few to zero points.
Also recall that late homework will not be accepted regardless of excuse. Treat the due date with respect. The real due
date is at midnight. Do not wait until the last minute!
7
