CS 101 - Introduction to Computing, Spring 2009

Lab 9

This lab assignment will have you write at least two methods in java that will create a new image that will show a portion from another image. This technique is called cropping.

Cropping of an image is to take a certain part of image and discard the rest of the image. Once the user has picked an image, we shall create an empty image which will store the resulting cropped image. Then we shall copy the pixels from the part of the original to the new image. "Copying the pixels" is nothing but copying the colors of pixels from original image to the new image. We have done cropping during lecture in Lect312c.java.

Lab Assignment 9

Create a Java program that will:

1. Contain a comment indicating
   • your Name,
   • Net-ID,
   • Course Name,
   • Assignment Name and
   • a short description of the assignment

2. Contain the main() method that will
   • allow the user to select a file using pickAFile().
   • call the method cropImage () twice.
   • display the image returned by each call to the method cropImage ().
   • allow the user to save each image returned by the calls to the method cropImage () where the name of the file is determined by using the pickAFile() method from the FileChooser class.

   Each call will send the image selected but must crop a different section of the image and crop a different sized section image. You are to crop an interesting item from the original image and not just some random location. You will also be required to submit your image with your JES program file. The BlendIn.jpg image offers a few interesting spots that could be cropped. You may use this image or any other image of your choosing. You may wish to use the picture explore() method to help find the x and y coordinates of different interesting sections of an image. Make sure you submit the image with your code when you turn in this program!

3. Contain a method called cropImage () that will:
   • take 5 parameters:
     1. the image to be cropped
     2. the x position were the cropping is to start
     3. the y position were the cropping is to start
     4. the x position were the cropping is to end
     5. the y position were the cropping is to end
   • verify that the starting x position is less than the ending x position
   • verify that the starting y position is less than the ending y position
   • verify that the x and y positions are within the boundaries of the original image
   • create a new empty image just large enough to hold the cropped image. You are expected to use Picture (width, height) constructor for this.
   • copy the pixels from the original images passed in as the parameter to the new image
   • return the new cropped image

   This method may call other methods that are in a library or that you have written. Note that the code given in lecture is close to what is needed here but it is not exact. If any of the verify checks fail, print out a good error message and return from the function.

Submittal of the Lab Assignment

• When saving your program, use a meaningful name like lab9.java.
• You are also to submit the Java file electronically by using the UNIX turnin command.
• You are also required to submit the image that you selected the x-start, y-start, x-end and y-end values.

  To use the UNIX turnin command to electronically hand-in your html file using the project name of lab9. To submit the files in lab9.java and BlendIn.jpg for lab9, the turnin command is entered as:

       turnin -c cs101 -p lab9 lab9.java BlendIn.jpg
  

  To verify what you submitted using the turnin command type:

       turnin -c cs101 -p lab9 -v