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 * Image processing operations for SciJava Ops.
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package org.scijava.ops.image.filter.pad;

import java.util.function.BiFunction;
import java.util.function.Function;

import net.imglib2.Dimensions;
import net.imglib2.FinalDimensions;
import net.imglib2.Interval;
import net.imglib2.RandomAccessibleInterval;
import net.imglib2.type.numeric.ComplexType;
import net.imglib2.util.Util;
import net.imglib2.view.Views;

import org.scijava.ops.spi.OpDependency;

/**
 * Op used to pad a kernel and shift the center of the kernel to the origin
 *
 * @author Brian Northan
 * @param <T>
 * @param <I>
 * @param <O>
 * @implNote op names='filter.padShiftKernel'
 */
public class PadShiftKernel<T extends ComplexType<T>, I extends RandomAccessibleInterval<T>, O extends RandomAccessibleInterval<T>>
	implements BiFunction<I, Dimensions, O>
{

	@OpDependency(name = "filter.padIntervalCentered")
	private BiFunction<I, Dimensions, Interval> paddingIntervalCentered;

	@OpDependency(name = "filter.padIntervalOrigin")
	private BiFunction<I, Interval, Interval> paddingIntervalOrigin;

	/**
	 * TODO
	 *
	 * @param kernel
	 * @param paddedDimensions
	 * @return the output
	 */
	@Override
	@SuppressWarnings("unchecked")
	public O apply(final I kernel, final Dimensions paddedDimensions) {

		Dimensions paddedFFTInputDimensions;

		// if an fftsize op has been set recompute padded size
		if (getFFTSizeOp() != null) {
            var sizes = getFFTSizeOp().apply(paddedDimensions);

			paddedFFTInputDimensions = new FinalDimensions(sizes[0]);
		}
		else {
			paddedFFTInputDimensions = paddedDimensions;

		}

		// compute where to place the final Interval for the kernel so that the
		// coordinate in the center
		// of the kernel is shifted to position (0,0).

		final var kernelConvolutionInterval = paddingIntervalCentered.apply(
			kernel, paddedFFTInputDimensions);

		final var kernelConvolutionIntervalOrigin = paddingIntervalOrigin
			.apply(kernel, kernelConvolutionInterval);

		return (O) Views.interval(Views.extendPeriodic(Views.interval(Views
			.extendValue(kernel, Util.getTypeFromInterval(kernel).createVariable()),
			kernelConvolutionInterval)), kernelConvolutionIntervalOrigin);

	}

	protected Function<Dimensions, long[][]> getFFTSizeOp() {
		return null;
	}

}
