import java.awt.*;
import java.awt.image.*;
import java.applet.*;
import java.net.*;
import java.io.*;
import java.lang.Math;
import java.util.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.JApplet;
import javax.imageio.*;
import javax.swing.event.*;
import java.util.*;

public class nonmax {

	static double[] input;
	static double[] output;
	int progress;
	int width;
	int height;
	int convolveX[] = {-1, 0, 1, -1, 0, 1, -1, 0, 1};
	int convolveY[] = {-1, -1, -1, 0, 0, 0, 1, 1, 1};
	int templateSize = 3;
	public void nonmax() {
			progress=0;
		}

		public void init(double[] inputIn, int widthIn, int heightIn) {
			width=widthIn;
			height=heightIn;
			input = inputIn;
			output = new double[width*height];

		}
		public double[] process() {
			progress=0;
			
			// first convolute image with x and y templates
			double diffx[] = new double[width*height];
			double diffy[] = new double[width*height];			
			double mag[] = new double[width*height];
			
			double valx, valy;
		
			for(int x = templateSize / 2; x < width - (templateSize / 2); x++) {
				for(int y= templateSize / 2; y < height- (templateSize / 2); y++) {
					valx = 0;
					valy = 0;					
					for(int x1 = 0; x1 < templateSize; x1++) {
						for(int y1 = 0; y1 < templateSize; y1++) {
							int pos = (y1 * templateSize + x1);
							int imPos = (x + (x1 - (templateSize / 2))) + ((y + (y1 - (templateSize / 2))) * width);
							
							valx +=((input[imPos]) * convolveX[pos]);
							valy +=((input[imPos]) * convolveY[pos]);
						}
					}
					diffx[x + (y * width)] = valx;
					diffy[x + (y * width)] = valy;
					mag[x + (y * width)] = Math.sqrt((valx * valx) + (valy * valy));
				}
			}

			for(int x = 1; x < width - 1; x++) {
				progress++;
				for(int y = 1 ; y < height - 1; y++) {
					int dx, dy;
					
					if(diffx[x + (y * width)] > 0) dx = 1;
					else dx = -1;

					if(diffy[x + (y * width)] > 0) dy = 1;
					else dy = -1;					
						
					double a1, a2, b1, b2, A, B, point, val;
					if(Math.abs(diffx[x + (y * width)]) > Math.abs(diffy[x + (y * width)]))
					{
						a1 = mag[(x+dx) + ((y) * width)];
						a2 = mag[(x+dx) + ((y-dy) * width)];
						b1 = mag[(x-dx) + ((y) * width)];
						b2 = mag[(x-dx) + ((y+dy) * width)];
						A = (Math.abs(diffx[x + (y * width)]) - Math.abs(diffy[x + (y * width)]))*a1 + Math.abs(diffy[x + (y * width)])*a2;
						B = (Math.abs(diffx[x + (y * width)]) - Math.abs(diffy[x + (y * width)]))*b1 + Math.abs(diffy[x + (y * width)])*b2;
						point = mag[x + (y * width)] * Math.abs(diffx[x + (y * width)]);
						if(point >= A && point > B) {
							val = Math.abs(diffx[x + (y * width)]);
							output[x + (y * width)] = val;
						}
						else {
							val = 0;
							output[x + (y * width)] = val;
						}
					}
					else 
					{
						a1 = mag[(x) + ((y-dy) * width)];
						a2 = mag[(x+dx) + ((y-dy) * width)];
						b1 = mag[(x) + ((y+dy) * width)];
						b2 = mag[(x-dx) + ((y+dy) * width)];						
						A = (Math.abs(diffy[x + (y * width)]) - Math.abs(diffx[x + (y * width)]))*a1 + Math.abs(diffx[x + (y * width)])*a2;
						B = (Math.abs(diffy[x + (y * width)]) - Math.abs(diffx[x + (y * width)]))*b1 + Math.abs(diffx[x + (y * width)])*b2;
						point = mag[x + (y * width)] * Math.abs(diffy[x + (y * width)]);
						if(point >= A && point > B) {
							//System.out.println("Setting value: " + (diffy[x + (y * width)]&0xff));
							val = Math.abs(diffy[x + (y * width)]);
							output[x + (y * width)] = val;
						}
						else {
							val = 0;
							output[x + (y * width)] = val;
						}							
					}
				}
			}
			
			return output;
		}
	
		public int getProgress() {
			return progress;
		}

	}