//changed the signature of Khai's function
	public static int byteToInteger(byte b) {
		return (short) ((short) b & 0xff);
	}


	public static int[] correctedPixels(byte [] pixels)
	{
		int [] corrected_pixels = new int[pixels.length];

		for(int i = 0 ; i < pixels.length ; i++)
				corrected_pixels[i] = byteToInteger(pixels[i]);


		return corrected_pixels;
	}


	/*
	 * Predictive Coding
	 */
	public static int[] applyPredictiveCoding(int option, int[] channel, int width)
	{
		int [] pc_errors = new int[channel.length];
		int A = 0, B = 0, C = 0;

		for(int i = 0 ; i < pc_errors.length ; i++)
		{

			if( i % width == 0 || i < width)
			{
				pc_errors[i] = channel[i];
				continue;
			}

			if(option != 1)
			{
				A = channel[i - 1];
				B = channel[i - width];
				C = channel[i - width - 1];
			}


			switch(option)
			{
				case 1:
					return channel;
//					break;

				case 2:
					pc_errors[i] = (channel[i] - A);
					break;

				case 3:
					pc_errors[i] = (channel[i] - B);
					break;

				case 4:
					pc_errors[i] = (channel[i] - C);
					break;

				case 5:
					pc_errors[i] = (channel[i] - ((A + B + C) / 3));
					break;

				case 6:
					pc_errors[i] = (channel[i] - (A + B - C));
					break;

				case 7:
					pc_errors[i] = (channel[i] - ((A + B) /2));
					break;

				case 8:
					if( (B - C > 0) && (A - C > 0) )
						pc_errors[i] = channel[i] - (int) (C + Math.sqrt(Math.pow(B-C, 2) + Math.pow(A-C, 2))) ;
					else if( (B - C < 0) && (A - C < 0) )
						pc_errors[i] = channel[i] - (int) (C + Math.sqrt(Math.pow(B-C, 2) + Math.pow(A-C, 2))) ;
					else
						pc_errors[i] = channel[i] - ((A + B) /2);
					break;

				default:
					//wrong input
					break;

			}

		}

		return pc_errors;
	}

	public static int[] removePredictiveCoding(int option, int[] pc_errors, int width)
	{
		int [] channel = new int[pc_errors.length];
		int A = 0, B = 0, C = 0;

		for(int i = 0 ; i < channel.length ; i++)
		{

			if( i % width == 0 || i < width)
			{
				channel[i] = pc_errors[i];
				continue;
			}

			if(option != 1)
			{
				A = pc_errors[i - 1];
				B = pc_errors[i - width];
				C = pc_errors[i - width - 1];
			}


			switch(option)
			{
				case 1:
					return pc_errors;
//					break;

				case 2:
					channel[i] = (pc_errors[i] + A);
					break;

				case 3:
					channel[i] = (pc_errors[i] + B);
					break;

				case 4:
					channel[i] = (pc_errors[i] + C);
					break;

				case 5://correct from here
					channel[i] = (pc_errors[i] + ((A + B + C) / 3));
					break;

				case 6:
					channel[i] = (pc_errors[i] + (A + B - C));
					break;

				case 7:
					channel[i] = (pc_errors[i] + ((A + B) /2));
					break;

				case 8:
					if( (B - C > 0) && (A - C > 0) )
						channel[i] = pc_errors[i] + (int) (C + Math.sqrt(Math.pow(B-C, 2) + Math.pow(A-C, 2))) ;
					else if( (B - C < 0) && (A - C < 0) )
						channel[i] = pc_errors[i] + (int) (C + Math.sqrt(Math.pow(B-C, 2) + Math.pow(A-C, 2))) ;
					else
						channel[i] = pc_errors[i] + ((A + B) /2);
					break;

				default:
					//wrong input
					break;

			}

		}

		return channel;
	}

	public static void main(String[] args) throws MagickException {

		Image test = new Image("Tulips.jpg");

		byte[] red = test.getLayer(0);
		int[] int_red = correctedPixels(red);
		int[] pc = applyPredictiveCoding(2,int_red,test.w);
	}
}