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. In lecture, we wrote code that copied an entire image to another in Lect39a.java. The important part of that code is something like the code below:
We have also showed how to access only a portion if an images in Lect34e.java. The important part of that code is shown below:
public static Picture copyImage (Picture p1) { // set up my return variable Picture p2; p2 = new Picture (p1.getWidth(), p1.getHeight() ); // access each pixel to modify it. Pixel pixelArray[] = p1.getPixels(); for (int count = 0 ; count < pixelArray.length ; count++) { // access the original pixel and information from that pixel Pixel pix1 = pixelArray [ count]; int redAmount = pix1.getRed (); int greenAmount = pix1.getGreen (); int blueAmount = pix1.getBlue (); int xPos = pix1.getX(); int yPos = pix1.getY(); // determine the position the pixel in the new picture int newX = xPos; int newY = yPos; Pixel pix2 = p2.getPixel (newX, newY); // set the proper information for the pixel in the new picture pix2.setRed (redAmount); pix2.setGreen (greenAmount); pix2.setBlue (blueAmount); } return p2; }
The above code accesses the 125x150 pixel portion of the picture from the X coordinates from 150 to 275 and the Y coordinates from 400 to 550. These pixel position are called the startX, endX, startY and endY values:
// accessing a portion of an image Picture p = new Picture (400, 600); Pixel arr[] = p.getPixels(); for (int count = 0; count < arr.length; count++) { Pixel pix = arr[count]; int xPos = pix.getX(); int yPos = pix.getY(); // access the 125x150 pixel portion of the picture if ( ((xPos >= 150) && (xPos < 275)) && ((yPos >= 400) && (yPos < 550)) ) { pix.setRed (0); } }
The above code just changes the color value at those pixels. It does NOT do any cropping. In order to do cropping, those pixels must be copied from that portion of the picture to a new blank picture.
In this example, this new blank picture would need to be 125 pixels wide and 150 pixels high. These values are determined by subtracting the endX value from the startX value and subtracting the endY value from the startY value.
When copying the pixels from the original picture to the new picture, we will also need to move the pixels to there proper X and Y coordinates in the new picture. In the above example, the original pixel at position (150, 400) needs to be placed at position (0, 0). The original pixel at position (200, 500) needs to be placed at potition (50, 100). This translation is easy to do since we just have to subtract the startX value from the original X coordinate and subtract the startYvalue from the original Y coordinate.
Create a Java program that will:
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. Here is another image that offers a few good spots for cropping, apollo-11-astronauts.jpg. 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!
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.
For example for lab2, name it Lab2yournetid.java, for example if your Net ID is sfranz3, the filename would be Lab2sfranz3.javaPlease only submit source code file (the .java file, not the .class). Also, if you have any comment about your program, please write it down in the same file; please do NOT write in the "Comments" field on the submission page (this will go into a different file and will be easily missed).
