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BoofCV is an open source Java library for real-time computer vision and robotics applications.
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/*
 * Copyright (c) 2023, Peter Abeles. All Rights Reserved.
 *
 * This file is part of BoofCV (http://boofcv.org).
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package boofcv.alg.distort.brown;

import boofcv.struct.distort.Point2Transform2_F64;
import georegression.misc.GrlConstants;
import georegression.struct.point.Point2D_F64;
import org.jetbrains.annotations.Nullable;

/**
 * Converts the observed distorted normalized image coordinates into undistorted normalized image coordinates.
 *
 * @author Peter Abeles
 */
@SuppressWarnings({"NullAway.Init"})
public class RemoveBrownNtoN_F64 implements Point2Transform2_F64 {

	// distortion parameters
	protected RadialTangential_F64 params;

	private double tol = GrlConstants.DCONV_TOL_A;

	public RemoveBrownNtoN_F64() {}

	public RemoveBrownNtoN_F64( double tol ) {
		this.tol = tol;
	}

	public void setTolerance( double tol ) {
		this.tol = tol;
	}

	public RemoveBrownNtoN_F64 setDistortion( @Nullable /**/double[] radial, /**/double t1, /**/double t2 ) {
		params = new RadialTangential_F64(radial, t1, t2);
		return this;
	}

	/**
	 * Removes radial distortion
	 *
	 * @param x Distorted x-coordinate normalized image coordinate
	 * @param y Distorted y-coordinate normalized image coordinate
	 * @param out Undistorted normalized coordinate.
	 */
	@Override public void compute( double x, double y, Point2D_F64 out ) {
		removeRadial(x, y, params.radial, params.t1, params.t2, out, tol);
	}

	@Override public RemoveBrownNtoN_F64 copyConcurrent() {
		var ret = new RemoveBrownNtoN_F64();
		ret.tol = tol;
		ret.params = new RadialTangential_F64(this.params);
		return ret;
	}

	/**
	 * Static function for removing radial and tangential distortion
	 *
	 * @param x Distorted x-coordinate normalized image coordinate
	 * @param y Distorted y-coordinate normalized image coordinate
	 * @param radial Radial distortion parameters
	 * @param t1 tangential distortion
	 * @param t2 tangential distortion
	 * @param out Undistorted normalized image coordinate
	 * @param tol convergence tolerance
	 */
	public static void removeRadial( double x, double y, double[] radial, double t1, double t2,
									 Point2D_F64 out, double tol ) {
		double origX = x;
		double origY = y;

		double prevSum = 0;

		for (int iter = 0; iter < 500; iter++) {

			// estimate the radial distance
			double r2 = x*x + y*y;
			double ri2 = r2;

			double sum = 0;
			for (int i = 0; i < radial.length; i++) {
				sum += radial[i]*ri2;
				ri2 *= r2;
			}

			double tx = 2.0*t1*x*y + t2*(r2 + 2.0*x*x);
			double ty = t1*(r2 + 2.0*y*y) + 2.0*t2*x*y;

			x = (origX - tx)/(1.0 + sum);
			y = (origY - ty)/(1.0 + sum);

			if (Math.abs(prevSum - sum) <= tol) {
				break;
			} else {
				prevSum = sum;
			}
		}
		out.setTo(x, y);
	}
}