package 
{

	/**
	 * @author nicoptere
	 */
	import flash.display.*;
	public class Thinning 
	{

		public static var W : int;
		public static var H : int;
		public static var L : int;
		
		public static var str : String = '';
		public static var output : String = '';

		public function Thinning ()
		{
		}

		static public function thin ( b : BitmapData, kernel : Array ) : BitmapData 
		{	
			var i : int;
			var j : int;
			var it : int;
			
			var result : Array = new Array( );
    
    
			W = b.width;
			H = b.height;
			L = W * H;


			if( str == '' )
			{
				b.lock( );
				for( i = 0; i < H ; ++i ) 
				{
					for( j = 0; j < W ; ++j ) 
					{
						if( b.getPixel( j, i ) == 0xFFFFFF )
						{
							str += '1';
						}else
						{
							str += '0';
						}
					}	
				}
				b.unlock( );
			}
			
			result = HitMiss( kernel );
			
			it = result.length;
			while(it--) 
			{
				i = result[it];
				str = str.substr( 0, i ) + '0' + str.substr( i + 1, str.length );
			}
			
			output = str;
			return b;
		}

		static function fromString ( x : int, y : int ) : int
		{
			var i : int = int( str.charAt( ( y * W ) + x % W ) );
			return i; 
		}

		static function HitMiss ( kernel : Array ) : Array
		{
   
			var output : Array = new Array( );
			var i : int;
			var X : int;
			var Y : int;
			
			for( i = 0; i < L ; i++ ) 
			{
				if( str.charAt( i ) == '1')
				{
					X = i % W;
					Y = int( i / W );
					if( kernelMatch( X, Y, kernel ) ) 
					{
							
						output.push( ( Y * W ) + X % W );
					}
				}
			}
			return output;
		}

		static function kernelMatch ( x : int, y : int, kernel : Array ) : Boolean
		{
	
			var matched : int = 0;
			var X : int;
			var Y : int;
			var ID : int;
			//table index
			for( var i : int = -1; i < 2 ; ++i )
			{
				for( var j : int = -1; j < 2 ; ++j )
				{
					X = x + i;
					Y = y + j;
					if( X >= 0 && X < W && Y >= 0 && Y < H )
					{
						ID = fromString( X, Y );
						
						if(  ( kernel[ ( ( j + 1 ) * 3 ) + ( i + 1 ) ] == 2 ) || ( ( ID == 1 ) && ( kernel[ ((j + 1) * 3) + (i + 1) ] == 1 ) || ( ID == 0 ) && kernel[ ((j + 1) * 3) + (i + 1) ] == 0 )
						)
						{
							++matched;
						}
					}
				}
			}
			if( matched == 9 )
			{
				return true;
			}
			return false;
		}
	}
}