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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *      https://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  
18  /*
19   * This is not the original file distributed by the Apache Software Foundation
20   * It has been modified by the Hipparchus project
21   */
22  package org.hipparchus.transform;
23  
24  /**
25   * This enumeration defines the various types of normalizations that can be
26   * applied to discrete sine transforms (DST). The exact definition of these
27   * normalizations is detailed below.
28   *
29   * @see FastSineTransformer
30   */
31  public enum DstNormalization {
32      /**
33       * Should be passed to the constructor of {@link FastSineTransformer} to
34       * use the <em>standard</em> normalization convention. The standard DST-I
35       * normalization convention is defined as follows
36       * <ul>
37       * <li>forward transform: y<sub>n</sub> = &sum;<sub>k=0</sub><sup>N-1</sup>
38       * x<sub>k</sub> sin(&pi; nk / N),</li>
39       * <li>inverse transform: x<sub>k</sub> = (2 / N)
40       * &sum;<sub>n=0</sub><sup>N-1</sup> y<sub>n</sub> sin(&pi; nk / N),</li>
41       * </ul>
42       * where N is the size of the data sample, and x<sub>0</sub> = 0.
43       */
44      STANDARD_DST_I,
45  
46      /**
47       * Should be passed to the constructor of {@link FastSineTransformer} to
48       * use the <em>orthogonal</em> normalization convention. The orthogonal
49       * DCT-I normalization convention is defined as follows
50       * <ul>
51       * <li>Forward transform: y<sub>n</sub> = &radic;(2 / N)
52       * &sum;<sub>k=0</sub><sup>N-1</sup> x<sub>k</sub> sin(&pi; nk / N),</li>
53       * <li>Inverse transform: x<sub>k</sub> = &radic;(2 / N)
54       * &sum;<sub>n=0</sub><sup>N-1</sup> y<sub>n</sub> sin(&pi; nk / N),</li>
55       * </ul>
56       * which makes the transform orthogonal. N is the size of the data sample,
57       * and x<sub>0</sub> = 0.
58       */
59      ORTHOGONAL_DST_I
60  }