Simple pixel tracer

gistfile1.pde

// simple-trace pixel-images
//
 
 
 
int w2,h2;
 
int[] values;
int[][] pairs;
 
void setup ()
{
    size( 200, 200 );
    w2 = width/10;
    h2 = height/10;
    values = new int[w2*h2];
    pairs = new int[values.length][];
    for ( int i =0; i<values.length; i++ )
    {
        values[i] = random(1000) > 500 ? 1 : 0;
        pairs[i] = new int[]{
            -1,-1,-1,-1                        };
    }
}
 
void draw()
{
    noStroke();
    for ( int i = 0; i< values.length; i++ )
    {
        fill( values[i] == 0 ? 0xFF000000 : 0xFFFFFFFF );
        int y = i/w2;
        int x = i - (y*w2);
        rect( x*10, y*10, 10, 10 );
        if ( values[i] == 0 )
        {
            int iRight = i+1;
            boolean r = false;
            if ( x < w2-1 && values[i] == values[iRight] )
            {
                pairs[i][1] = iRight; 
                r = true;
            }
            if ( y < h2-1 )
            {
                boolean rb = false;
                int iRightBelow = iRight + w2;
                if ( x < w2-1 && values[i] == values[iRightBelow] )
                {
                    rb = true;
                    pairs[i][2] = iRightBelow;
                }
                int iBelow = i + w2;
                if ( values[i] == values[iBelow] )
                {
                    pairs[i][3] = iBelow;
                }
 
                int iBelowLeft = iBelow-1;
                if ( x != 0 && pairs[i-1][2] != iBelow && values[i] == values[iBelowLeft] )
                {
                    pairs[i][0] = iBelowLeft;
                }
            }
        }
    }
 
    noFill(); 
    stroke(0xFF00FF00);
    for ( int i = 0; i< pairs.length; i++ )
    {
        if ( pairs[i][0] != -1 ) drawLine( i, pairs[i][0] );
        if ( pairs[i][1] != -1 ) drawLine( i, pairs[i][1] );
        if ( pairs[i][2] != -1 ) drawLine( i, pairs[i][2] );
        if ( pairs[i][3] != -1 ) drawLine( i, pairs[i][3] );
    }
}
 
void drawLine ( int i1, int i2 )
{
    int y1 = i1/w2;
    int x1 = i1 - (y1*w2);
    int y2 = i2/w2;
    int x2 = i2 - (y2*w2);
    line( x1*10+5, y1*10+5, x2*10+5, y2*10+5 );
}
 
void keyPressed ()
{
    switch ( key )
    {
    case '1':
 
        values = new int[w2*h2];
        pairs = new int[values.length][];
        for ( int i =0; i<values.length; i++ )
        {
            values[i] = random(1000) > 500 ? 1 : 0;
            pairs[i] = new int[]{
                -1,-1,-1,-1                                    };
        }
        break;
    }
 
}