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/*
 * Copyright (c) 2021, 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.struct.feature;

/**
 * Precomputes the output of sine/cosine operations. Given an angle it will
 * return an approximation much faster than computing it from scratch.
 *
 * @author Peter Abeles
 */
// todo place in ConnectLinesGrid
// todo          HoughTransformLinePolar
public class CachedSineCosine_F32 {

	// minimum angle in the table
	float minAngle;
	// Maximum angle in the table
	float maxAngle;
	// radians between each step
	float delta;

	// cosine table
	public float[] c;
	// sine table
	public float[] s;

	public CachedSineCosine_F32( float minAngle, float maxAngle, int size ) {
		this.minAngle = minAngle;
		this.maxAngle = maxAngle;
		this.delta = (maxAngle - minAngle)/size;

		c = new float[size];
		s = new float[size];

		for (int i = 0; i < size; i++) {
			float angle = (maxAngle - minAngle)*i/size + minAngle;
			c[i] = (float)Math.cos(angle);
			s[i] = (float)Math.sin(angle);
		}
	}

	public float cosine( float value ) {
		return interpolate(value, c);
	}

	public float sine( float value ) {
		return interpolate(value, s);
	}

	private float interpolate( float value, float[] table ) {
		float v = value - minAngle;
		int i = (int)v;
		if (i < 0)
			return table[0];
		else if (i >= table.length - 1)
			return table[table.length - 1];

		float w = v - i;
		return table[i]*(1f - w) + table[i + 1]*w;
	}

	public int computeIndex( float angle ) {
		return (int)((angle - minAngle)/delta);
	}
}