Changelog
• 9/18: Signature of method saveImage modi�ed to include a second paramete
Description
The purpose of this assignment is to practice object oriented programming principles in Java combined
with command line arguments, �le I/O operations, and memory management with a
ays.
Instructions
Validation : Make sure all method parameters are properly validated (e.g. String[] args can’t be
empty, etc.)
Documentation : Comments in JavaDoc-style are required. You must comment each class, each
method and each instance/class variable you declare. You must also comment any piece of code
that is not obvious what it does.
Visibility : All �elds should be made private unless we explicitly say otherwise. All methods provided
in the speci�cation are public.
Packages : You may not import any classes except Scanner, File, PrintWrite
Mohammad Qasim
Submission
Submission instructions are as follows:
)
Grading
• Grading is based on both automated unit-testing and manual code inspection
• If your code doesn’t compile, you will get zero points
Testing
You will start programming without a tester. The goal is to help you put more focus on writing logically
co
ect programs instead of trying to pass certain tests only. At some point next week, a tester will also
e made available. But don’t wait for it in order to start your project. You won’t have enough time to
complete the project on time if you wait for the tester!
Background
A digital image with dimensions HxW is represented with a matrix of pixels that has H rows and W
columns. In grayscale images, each pixel is an integer that takes values from XXXXXXXXXXi.e. 1 byte). A value of
zero co
esponds to the black color and a value of 255 co
esponds to the white color. Everything in
etween is a tone of gray; the darker the gray the closer to 0, the lighter the gray the closer to 255. Figure
1a depicts a zoom-in on a 16x12 grayscale image. In Figure 1b you see the values of each pixel
superimposed on the image. And in Figure 1c you see the 2D representation of this grayscale image.
XXXXXXXXXXa b c
Figure 1: Grayscale image represenation
Images come in many diFerent formats, but to keep things simple for this project, we will use the PGM
format (portable graymap format). PGM images can be stored in either a binary or a text format. We will
use the text format to make the reading/writing of the images and the debugging of the code even
simpler – it will be easy to visually inspect the input you use and the output you generate. Most photo
viewing/editing applications support this format, but in case yours doesn’t, you can download GIMP for
free (you’re not required to use a photo app, but the whole project will make more sense if you do). In the
snippet below, you can see an example of an actual image stored in a PGM �le.
P2
24 7
255
XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX
XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX
XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX
XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX
XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX
XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX
XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX
The �rst row is the code P2 that indicates the format of the �le. The second row contains the width and
the height of the image in pixels (24 and 7 respectively). The third row de�nes the maximum grayscale
value which is 255 in this project (minimum is 0 by default). And what follows is simply a series of
width⨯height pixel values. Open your favorite plain-text editor, copy+paste the above snippet, and save
the �le as image.pgm (make sure it’s in plain text format). Then, open it
with your favorite photo viewing/editing application (e.g. Photoshop) to
verify that it looks like the �gure on the right (you will need to zoom-in a
lot because this image is very small).
https:
www.gimp.org
When it comes to color images, the only diFerence is that each pixel consists of three, instead of one,
values (see Figure 2 below). These three values co
espond to the three primary colors: Red, Green, Blue.
The theory behind it is the RGB color model but you do not need to know any details to complete this
project.
Figure 2: Color image representation
In terms of the �le format, we will use a very similar to the previous version, called portable pixmap
format (PPM). This is again a text-based format, so reading/writing of images and code debugging will
emain simple. The following is an example of such a �le. On the left is the actual plain-text content of the
�le that you can create/edit with any plain-text editor, and on the right is the image you will see if you
open that �le with a photo viewing/editing application (you will need to zoom-in a lot because this image
is extremely small).
P3
3 2
255
XXXXXXXXXX
XXXXXXXXXX
XXXXXXXXXX
XXXXXXXXXX
XXXXXXXXXX
XXXXXXXXXX
The �rst row is the code P3 that indicates the PPM text format. The second row contains the width and
the height of the image in pixels (3 and 2 respectively). The third row de�nes the maximum color value
which is 255 in this project (minimum is 0 by default). And what follows is a series of width⨯height pixels
– each pixel is a 3-tuple (red green blue).
https:
en.wikipedia.org/wiki/RGB_color_model
Tasks
You must implement the following classes based on the speci�cation provided below. In most part, the
visibilities and the types of the variables are not provided; it’s your task to �gure out what is the proper
visibility and type to use in each case.
ImagingApp
This is the entry point to your executable application. We want to be able to use a command line
argument when we run the application. Execution in the terminal should look like this:
java ImagingApp input_file output_file operation parameters
input_file
the name of the PGM or PPM �le that will be used as input image
output_file
the name of the PGM or PPM �le that will be used as output image
operation
a string that indicates what imaging operation should be applied on the input image before it is
saved as the output image. The following are the possible values:
"scale" for scaling the image
"crop" for cropping the image
"flip" for Lipping the image
"rotate" for rotating the image
"compress" for compressing the image
parameters
one or more command line arguments that further specify the details of the above operation.
The following are the options in each case:
scale is followed by one integer. If it’s positive (e.g. 3), the image is magni�ed that many
times (e.g. triples in both dimensions). If it’s negative (e.g. -2), the image is mini�ed that many
times (e.g. halves in both dimensions).
Example: java ImagingApp file1 file2 scale 4
crop is followed by four integers y x h w where y,x is the origin of the cropped region, h
is the height of the cropped region and w is the width of the cropped region.
Example: java ImagingApp file1 file2 crop XXXXXXXXXX
flip is followed by one string. If it’s "horizontal", the image is Lipped horizontally, and if
it’s "vertical", the image is Lipped vertically.
Example: java ImagingApp file1 file2 flip vertical
otate is followed by one string. If it’s "clockwise", the image is rotated 90 degrees
clockwise, and if it’s "counterclockwise", the image is rotated 90 degrees
counterclockwise.
Example: java ImagingApp file1 file2 rotate clockwise
compress is followed by two strings ttt ppp . The �rst one refers to tile compression, the
second one to pixel compression, and there are two possible values for each: yes / no
Example: java ImagingApp file1 file2 compress yes no
Fields
static Image inputImage
The input image that is constructed from the contents of the input_file , must be assigned to
this �eld.
static Image outputImage
The output image that is constructed from operations scale, crop, �ip, rotate, must be assigned to
this �eld.
static CompressedImage compressedImage
The output image that is constructed from operation compress, must be assigned to this �eld.
Methods
public static void main(String[] args)
All the handling of the command line arguments as well as the validation of the user input, takes
place in this method
oolean saveImage(Image img, String filename)
Saves the img into a PGM/PPM �le. Returns false if an e
or occurs, otherwise true.
oolean saveImage(CompressedImage img, String filename)
Saves the img into a PGM/PPM �le. Returns false if an e
or occurs, otherwise true.
Pixel
This class represents a single pixel in an image.
Fields
value
It’s an a
ay that holds the actual value of a pixel. For grayscale images, the