package pl.wroc.pwr.image.converter;

import pl.wroc.pwr.IOperator1P;
import pl.wroc.pwr.image.IRGBImage;
import pl.wroc.pwr.image.IYUVImage;
import pl.wroc.pwr.image.model.YUVImage;

/**
 * From: http://en.kioskea.net/contents/video/yuv-ycrcb.php3
 *
 * Y = 0.299R + 0.587 G + 0.114 B
 * U = -0.147R - 0.289 G + 0.436B = 0.492(B - Y)
 * V = 0.615R -0.515G -0.100B = 0.877(R-Y)
 *
 * @author Mariusz Paradowski
 */
public class RGBtoYUVConverter implements IOperator1P<IYUVImage, IRGBImage> {

	public IYUVImage apply(IRGBImage inputImage) {
		IYUVImage outputImage = new YUVImage(inputImage.getSize());
		for ( int i = 0; i < inputImage.getRedChannel( ).getMaxIndex( ); i++ ) {

			float R = inputImage.getRedChannel().getValue(i);
			float G = inputImage.getGreenChannel().getValue(i);
			float B = inputImage.getBlueChannel().getValue(i);

			float Y = 0.299f*R + 0.587f*G + 0.114f*B;
			float U = 0.492f*(B-Y);
			float V = 0.877f*(R-Y);

			outputImage.getLuminanceYChannel().setValue(i, Y);
			outputImage.getChrominanceUChannel().setValue(i, U);
			outputImage.getChrominanceVChannel().setValue(i, V);
		}
		return outputImage;
	}
}