package org.freehep.graphicsio.gif;

/* NeuQuant Neural-Net Quantization Algorithm
 * ------------------------------------------
 *
 * Copyright (c) 1994 Anthony Dekker
 *
 * NEUQUANT Neural-Net quantization algorithm by Anthony Dekker, 1994.
 * See "Kohonen neural networks for optimal colour quantization"
 * in "Network: Computation in Neural Systems" Vol. 5 (1994) pp 351-367.
 * for a discussion of the algorithm.
 * See also  http://www.acm.org/~dekker/NEUQUANT.HTML
 *
 * Any party obtaining a copy of these files from the author, directly or
 * indirectly, is granted, free of charge, a full and unrestricted irrevocable,
 * world-wide, paid up, royalty-free, nonexclusive right and license to deal
 * in this software and documentation files (the "Software"), including without
 * limitation the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons who receive
 * copies from any such party to do so, with the only requirement being
 * that this copyright notice remain intact.
 */

public class NeuQuant {

    public static final int ncycles	=	100;			// no. of learning cycles

    public static final int netsize  = 255;		// number of colours used
    public static final int specials  = 3;		// number of reserved colours used
    public static final int bgColour  = specials-1;	// reserved background colour
    public static final int cutnetsize  = netsize - specials;
    public static final int maxnetpos  = netsize-1;

    public static final int initrad	 = netsize/8;   // for 256 cols, radius starts at 32
    public static final int radiusbiasshift = 6;
    public static final int radiusbias = 1 << radiusbiasshift;
    public static final int initBiasRadius = initrad*radiusbias;
    public static final int radiusdec = 30; // factor of 1/30 each cycle

    public static final int alphabiasshift = 10;			// alpha starts at 1
    public static final int initalpha      = 1<<alphabiasshift; // biased by 10 bits

    public static final double gamma = 1024.0;
    public static final double beta = 1.0/1024.0;
    public static final double betagamma = beta * gamma;
    
    private double [] [] network = new double [netsize] [3]; // the network itself
    protected int [] [] colormap = new int [netsize] [4]; // the network itself
    
    private int [] netindex = new int [256]; // for network lookup - really 256
    
    private double [] bias = new double [netsize];  // bias and freq arrays for learning
    private double [] freq = new double [netsize];

    // four primes near 500 - assume no image has a length so large
    // that it is divisible by all four primes
   
    public static final int prime1	=	499;
    public static final int prime2	=	491;
    public static final int prime3	=	487;
    public static final int prime4	=	503;
    public static final int maxprime=	prime4;
    
    protected int [][] pixels = null;
    private int samplefac = 0;


    public NeuQuant (int sample, int[][] pixels) {
        if (sample < 1) throw new RuntimeException ("Sample must be 1..30");
        if (sample > 30) throw new RuntimeException ("Sample must be 1..30");
        samplefac = sample;
        setPixels (pixels);
		setUpArrays ();
    }
        
    public int getColorCount () {
    	return netsize;
    }

    public int[] getColorMap() {
    	// keep entry 0 free for transparent color
    	int[] c = new int[netsize+1];
    	c[0] = 0x00000000;
    	for (int i=0; i<netsize; i++) {
		    c[i+1] = (colormap[i][0]     )  |
	    	         (colormap[i][1] << 8)  |
	    	         (colormap[i][2] << 16) |
	    	         (0xFF           << 24);
    	}
    	return c;
    }

    protected void setUpArrays () {
    	network [0] [0] = 0.0;	// black
    	network [0] [1] = 0.0;
    	network [0] [2] = 0.0;
    	
    	network [1] [0] = 1.0;	// white
    	network [1] [1] = 1.0;
    	network [1] [2] = 1.0;

    	// RESERVED bgColour	// background
    	
        for (int i=0; i<specials; i++) {
		    freq[i] = 1.0 / netsize;
		    bias[i] = 0.0;
        }
        
        for (int i=specials; i<netsize; i++) {
		    double [] p = network [i];
		    p[0] = (256.0 * (i-specials)) / cutnetsize;
		    p[1] = (256.0 * (i-specials)) / cutnetsize;
		    p[2] = (256.0 * (i-specials)) / cutnetsize;

		    freq[i] = 1.0 / netsize;
		    bias[i] = 0.0;
        }
    }    	
    
    private void setPixels (int[][] pixels) {
        if (pixels.length*pixels[0].length < maxprime) throw new RuntimeException ("Image is too small");
        this.pixels = pixels;
    }
    
    public void init () {
        learn ();
        fix ();
        inxbuild ();
    }

    private void altersingle(double alpha, int i, double b, double g, double r) {
        // Move neuron i towards biased (b,g,r) by factor alpha
        double [] n = network[i];				// alter hit neuron
    	n[0] -= (alpha*(n[0] - b));
    	n[1] -= (alpha*(n[1] - g));
    	n[2] -= (alpha*(n[2] - r));
    }

    private void alterneigh(double alpha, int rad, int i, double b, double g, double r) {
        
    	int lo = i-rad;   if (lo<specials-1) lo=specials-1;
    	int hi = i+rad;   if (hi>netsize) hi=netsize;

    	int j = i+1;
    	int k = i-1;
    	int q = 0;
    	while ((j<hi) || (k>lo)) {
    	    double a = (alpha * (rad*rad - q*q)) / (rad*rad);
    	    q ++;
    		if (j<hi) {
    			double [] p = network[j];
    			p[0] -= (a*(p[0] - b));
    			p[1] -= (a*(p[1] - g));
    			p[2] -= (a*(p[2] - r));
    			j++;
    		}
    		if (k>lo) {
    			double [] p = network[k];
    			p[0] -= (a*(p[0] - b));
    			p[1] -= (a*(p[1] - g));
    			p[2] -= (a*(p[2] - r));
    			k--;
    		}
    	}
    }
    
    private int contest (double b, double g, double r) {    // Search for biased BGR values
    	// finds closest neuron (min dist) and updates freq 
    	// finds best neuron (min dist-bias) and returns position 
    	// for frequently chosen neurons, freq[i] is high and bias[i] is negative 
    	// bias[i] = gamma*((1/netsize)-freq[i]) 

    	double bestd = Float.MAX_VALUE;
    	double bestbiasd = bestd;
    	int bestpos = -1;
    	int bestbiaspos = bestpos;
        
    	for (int i=specials; i<netsize; i++) {
    		double [] n = network[i];
    		double dist = n[0] - b;   if (dist<0) dist = -dist;
    		double a = n[1] - g;   if (a<0) a = -a;
    		dist += a;
    		a = n[2] - r;   if (a<0) a = -a;
    		dist += a;
    		if (dist<bestd) {bestd=dist; bestpos=i;}
    		double biasdist = dist - bias [i];
    		if (biasdist<bestbiasd) {bestbiasd=biasdist; bestbiaspos=i;}
    		freq [i] -= beta * freq [i];
    		bias [i] += betagamma * freq [i];
    	}
    	freq[bestpos] += beta;
    	bias[bestpos] -= betagamma;
    	return bestbiaspos;
    }
    
    private int specialFind (double b, double g, double r) {
    	for (int i=0; i<specials; i++) {
    		double [] n = network[i];
    		if (n[0] == b && n[1] == g && n[2] == r) return i;
    	}
    	return -1;
    }
    
    private void learn() {
        int biasRadius = initBiasRadius;
    	int alphadec = 30 + ((samplefac-1)/3);
    	int lengthcount = pixels.length*pixels[0].length;
    	int samplepixels = lengthcount / samplefac;
    	int delta = samplepixels / ncycles;
    	int alpha = initalpha;

	    int i = 0;
    	int rad = biasRadius >> radiusbiasshift;
    	if (rad <= 1) rad = 0;
	
//    	System.err.println("beginning 1D learning: samplepixels=" + samplepixels + "  rad=" + rad);

        int step = 0;
        int pos = 0;
        
    	if ((lengthcount%prime1) != 0) step = prime1;
    	else {
    		if ((lengthcount%prime2) !=0) step = prime2;
    		else {
    			if ((lengthcount%prime3) !=0) step = prime3;
    			else step = prime4;
    		}
    	}
	
    	i = 0;
    	while (i < samplepixels) {
    	    int p = pixels [pos / pixels[0].length][pos % pixels[0].length];
	        int red   = (p >> 16) & 0xff;
	        int green = (p >>  8) & 0xff;
	        int blue  = (p      ) & 0xff;

    		double b = blue;
    		double g = green;
    		double r = red;

    		if (i == 0) {   // remember background colour
    			network [bgColour] [0] = b;
    			network [bgColour] [1] = g;
    			network [bgColour] [2] = r;
    		}

    		int j = specialFind (b, g, r);
    		j = j < 0 ? contest (b, g, r) : j;

			if (j >= specials) {   // don't learn for specials
            	double a = (1.0 * alpha) / initalpha;
    			altersingle (a, j, b, g, r);
    			if (rad > 0) alterneigh (a, rad, j, b, g, r);   // alter neighbours
    		}

    		pos += step;
    		while (pos >= lengthcount) pos -= lengthcount;
	        
    		i++;
    		if (i%delta == 0) {	
    			alpha -= alpha / alphadec;
    			biasRadius -= biasRadius / radiusdec;
    			rad = biasRadius >> radiusbiasshift;
    			if (rad <= 1) rad = 0;
    		}
    	}
//    	System.err.println("finished 1D learning: final alpha=" + (1.0 * alpha)/initalpha + "!");
    }

    private void fix() {
        for (int i=0; i<netsize; i++) {
            for (int j=0; j<3; j++) {
                int x = (int) (0.5 + network[i][j]);
                if (x < 0) x = 0;
                if (x > 255) x = 255;
                colormap[i][j] = x;
            }
            colormap[i][3] = i;
        }
    }

    private void inxbuild() {
        // Insertion sort of network and building of netindex[0..255]

    	int previouscol = 0;
    	int startpos = 0;

    	for (int i=0; i<netsize; i++) {
    		int[] p = colormap[i];
    		int[] q = null;
    		int smallpos = i;
    		int smallval = p[1];			// index on g
    		// find smallest in i..netsize-1
    		for (int j=i+1; j<netsize; j++) {
    			q = colormap[j];
    			if (q[1] < smallval) {		// index on g
    				smallpos = j;
    				smallval = q[1];	// index on g
    			}
    		}
    		q = colormap[smallpos];
    		// swap p (i) and q (smallpos) entries
    		if (i != smallpos) {
    			int j = q[0];   q[0] = p[0];   p[0] = j;
    			j = q[1];   q[1] = p[1];   p[1] = j;
    			j = q[2];   q[2] = p[2];   p[2] = j;
    			j = q[3];   q[3] = p[3];   p[3] = j;
    		}
    		// smallval entry is now in position i
    		if (smallval != previouscol) {
    			netindex[previouscol] = (startpos+i)>>1;
    			for (int j=previouscol+1; j<smallval; j++) netindex[j] = i;
    			previouscol = smallval;
    			startpos = i;
    		}
    	}
    	netindex[previouscol] = (startpos+maxnetpos)>>1;
    	for (int j=previouscol+1; j<256; j++) netindex[j] = maxnetpos; // really 256
    }

    public int convert (int pixel) {
        int alfa = (pixel >> 24) & 0xff;
	    int r   = (pixel >> 16) & 0xff;
	    int g = (pixel >>  8) & 0xff;
	    int b  = (pixel      ) & 0xff;
	    int i = inxsearch(b, g, r);
	    int bb = colormap[i][0];
	    int gg = colormap[i][1];
	    int rr = colormap[i][2];
	    return (alfa << 24) | (rr << 16) | (gg << 8) | (bb);
    }

    public int lookup (int pixel) {
	    int r = (pixel >> 16) & 0xff;
	    int g = (pixel >>  8) & 0xff;
	    int b = (pixel      ) & 0xff;
	    int i = inxsearch(b, g, r);
	    // compensate for transparent color
	    return i+1;
    }

    private int not_used_slow_inxsearch(int b, int g, int r) {
        // Search for BGR values 0..255 and return colour index
    	int bestd = 1000;		// biggest possible dist is 256*3
    	int best = -1;
    	for (int i = 0; i<netsize; i++) {
 			int [] p = colormap[i];
			int dist = p[1] - g;
			if (dist<0) dist = -dist;
			int a = p[0] - b;   if (a<0) a = -a;
			dist += a;
			a = p[2] - r;   if (a<0) a = -a;
			dist += a;
			if (dist<bestd) {bestd=dist; best=i;}
		}
		return best;
    }
    
    protected int inxsearch(int b, int g, int r) {
        // Search for BGR values 0..255 and return colour index
    	int bestd = 1000;		// biggest possible dist is 256*3
    	int best = -1;
    	int i = netindex[g];	// index on g
    	int j = i-1;		// start at netindex[g] and work outwards

    	while ((i<netsize) || (j>=0)) {
    		if (i<netsize) {
    			int [] p = colormap[i];
    			int dist = p[1] - g;		// inx key
    			if (dist >= bestd) i = netsize;	// stop iter
    			else {
    				if (dist<0) dist = -dist;
    				int a = p[0] - b;   if (a<0) a = -a;
    				dist += a;
    				if (dist<bestd) {
    					a = p[2] - r;   if (a<0) a = -a;
    					dist += a;
    					if (dist<bestd) {bestd=dist; best=i;}
    				}
    				i++;
    			}
    		}
    		if (j>=0) {
    			int [] p = colormap[j];
    			int dist = g - p[1]; // inx key - reverse dif
    			if (dist >= bestd) j = -1; // stop iter
    			else {
    				if (dist<0) dist = -dist;
    				int a = p[0] - b;   if (a<0) a = -a;
    				dist += a;
    				if (dist<bestd) {
    					a = p[2] - r;   if (a<0) a = -a;
    					dist += a;
    					if (dist<bestd) {bestd=dist; best=j;}
    				}
    				j--;
    			}
    		}
    	}

    	return best;
    }	
}