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 * Image processing operations for SciJava Ops.
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package org.scijava.ops.image.imagemoments.hu;

import org.scijava.ops.image.imagemoments.AbstractImageMomentOp;
import net.imglib2.RandomAccessibleInterval;
import net.imglib2.type.numeric.RealType;

import org.scijava.function.Computers;
import org.scijava.ops.spi.Op;
import org.scijava.ops.spi.OpDependency;

/**
 * Op to calculate the {@code imageMoments.huMoment3}.
 *
 * @author Daniel Seebacher (University of Konstanz)
 * @author Christian Dietz (University of Konstanz)
 * @param <I> input type
 * @param <O> output type
 * @see <a href=
 *      "https://en.wikipedia.org/wiki/Image_moment#Rotation_invariants"> This
 *      page </a>
 * @implNote op names='imageMoments.huMoment3', label='Image Moment: HuMoment3'
 */
public class DefaultHuMoment3<I extends RealType<I>, O extends RealType<O>>
	implements AbstractImageMomentOp<I, O>
{

	@OpDependency(name = "imageMoments.normalizedCentralMoment30")
	private Computers.Arity1<RandomAccessibleInterval<I>, O> normalizedCentralMoment30Func;

	@OpDependency(name = "imageMoments.normalizedCentralMoment12")
	private Computers.Arity1<RandomAccessibleInterval<I>, O> normalizedCentralMoment12Func;

	@OpDependency(name = "imageMoments.normalizedCentralMoment21")
	private Computers.Arity1<RandomAccessibleInterval<I>, O> normalizedCentralMoment21Func;

	@OpDependency(name = "imageMoments.normalizedCentralMoment03")
	private Computers.Arity1<RandomAccessibleInterval<I>, O> normalizedCentralMoment03Func;

	/**
	 * TODO
	 *
	 * @param input
	 * @param output
	 */
	@Override
	public void computeMoment(final RandomAccessibleInterval<I> input,
		final O output)
	{

		final var n30 = output.createVariable();
		normalizedCentralMoment30Func.compute(input, n30);
		final var n12 = output.createVariable();
		normalizedCentralMoment12Func.compute(input, n12);
		final var n21 = output.createVariable();
		normalizedCentralMoment21Func.compute(input, n21);
		final var n03 = output.createVariable();
		normalizedCentralMoment03Func.compute(input, n03);

		// term1 = (n30 - (3 * n12))^2
		final var term1 = n30.copy();
		output.set(n12);
		output.mul(3);
		term1.sub(output);
		term1.mul(term1);

		// term2 = ((3 * n21) - n03)^2
		final var term2 = n21.copy();
		output.setReal(3d);
		term2.mul(output);
		term2.sub(n03);
		term2.mul(term2);

		output.set(term1);
		output.add(term2);
//		output.setReal(Math.pow(n30.getRealDouble() - 3 * n12.getRealDouble(), 2)
//				+ Math.pow(3 * n21.getRealDouble() - n03.getRealDouble(), 2));
	}
}
