I am trying to set this Java program up correctly. It is supposed to read a PPM image file and then alter the image in someway. I've written the negateRed method to change red color values to their negative value. I have set up the array buffer to read in one row of image at a time according to assignment specifications. However, when I run the program to negate the red colors, it is only iterating through the first row of the image. How can I change this so that I iterate through values of the entire file?

import java.util.Scanner; import java.io.File; import java.io.PrintWriter;

public class PPM Image { public static void main ( String args[] ) { try { System.out.print ( " PPM Image Processor " ); Scanner keyboard = new Scanner ( System.in ); System.out.print ( " Enter input filename: " ); String inFile; inFile = keyboard.next(); File file = new File( inFile ); Scanner input = new Scanner ( file );

String first = input.next(); int columns = input.nextInt(); int row = input.nextInt(); int max = input.nextInt(); int x = ( columns * 3 ); int y = 0; int buffer[] = new int [x];

Scanner keyboardTwo = new Scanner ( System.in ); String outFile; System.out.print ( "Enter output filename: " ); outFile = keyboardTwo.next();

PrintWriter writer = new PrintWriter ( outFile ); writer.println ( first ); writer.print ( columns ); writer.printf ( " %d", row ); writer.printf ( " %d ", max ); while ( y < x ) { int v = input.nextInt(); buffer[y] = v; y++; }

negateRed ( buffer, x );

for ( int i = 0; i < buffer.length; i++ ) { writer.println ( buffer[i] ); } writer.close(); }

catch ( Exception ex ) { System.out.println ( "An error has occurred!" ); ex.printStackTrace(); } } /** * negateRed * * This method negates the red value in the image. All P3-format * PPM images have an image depth of 255, which are used in * the method's calculations. * * @param buffer an integer array containing the image buffer * @param x an integer w/ the number of columns in the image * @return NONE */ public static void negateRed ( int [] buffer, int x ) { for ( int i = 0; i < x; i++ ) { if ( i % 3 == 0 ) buffer[i] = 255 - buffer[i]; } } }