devela/phys/wave/
alloc.rs

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1// devela::phys::wave::alloc
2//
3//! Wavelet items that allocate.
4//
5// TOC
6// - definitions
7//   - trait WaveletCompressionVec
8//   - trait WaveletTransformVec
9//   - struct WaveletUnitVec
10// - impls for WaveletHaar
11
12use crate::{vec_ as vec, Vec, WaveletHaar, WaveletUnitRole};
13
14#[cfg(feature = "_float_f64")]
15#[allow(unused_imports, reason = "!std: abs")]
16use crate::ExtFloat;
17
18/// Trait for lossy compression of wavelet coefficients.
19///
20/// Compresses coefficients based on a given tolerance, zeroing out those
21/// deemed insignificant to the desired error threshold.
22pub trait WaveletCompressionVec {
23    /// Compresses wavelet coefficients by thresholding small values.
24    fn compress(&self, coeffs: &[f64], tolerance: f64) -> Vec<f64>;
25}
26
27/// Trait defining essential wavelet transform operations.
28pub trait WaveletTransformVec {
29    /// Computes the forward wavelet transform on the given input.
30    #[must_use]
31    fn forward(&self, input: &[f64]) -> Vec<f64>;
32
33    /// Computes the inverse wavelet transform on the given coefficients.
34    #[must_use]
35    fn inverse(&self, coeffs: &[f64]) -> Vec<f64>;
36}
37
38/// A single unit of the wavelet decomposition at a specific level and position.
39pub struct WaveletUnitVec {
40    /// The type of the wavelet component (scaling or wavelet).
41    pub component_type: WaveletUnitRole,
42    /// Resolution level of the component, indicating its level of detail.
43    pub level: usize,
44    /// Position index of the component within the resolution level.
45    pub position: usize,
46    /// Coefficient values defining the component's shape.
47    pub values: Vec<f64>,
48}
49
50impl WaveletUnitVec {
51    /// Creates a new wavelet component of a specified type, level, position, and values.
52    pub fn new(
53        component_type: WaveletUnitRole,
54        level: usize,
55        position: usize,
56        values: Vec<f64>,
57    ) -> Self {
58        Self { component_type, level, position, values }
59    }
60}
61
62/* impls for WaveletHaar */
63
64impl WaveletCompressionVec for WaveletHaar {
65    fn compress(&self, coeffs: &[f64], tolerance: f64) -> Vec<f64> {
66        coeffs.iter().map(|&c| if c.abs() < tolerance { 0.0 } else { c }).collect()
67    }
68}
69
70impl WaveletTransformVec for WaveletHaar {
71    fn forward(&self, input: &[f64]) -> Vec<f64> {
72        let mut output = input.to_vec();
73        let mut length = output.len();
74
75        // Iteratively apply averaging and differencing until we reach the coarsest level.
76        while length > 1 {
77            let mut temp = vec![0.0; length];
78            for i in 0..length / 2 {
79                // Calculate average and detail coefficients for each pair.
80                let average = (output[2 * i] + output[2 * i + 1]) / 2.0;
81                let difference = (output[2 * i] - output[2 * i + 1]) / 2.0;
82                temp[i] = average;
83                temp[length / 2 + i] = difference; // Store details in the second half
84            }
85            // Copy temporary results back to output for the next level.
86            output[..length].clone_from_slice(&temp);
87            length /= 2; // Reduce length to work on the next coarser level
88        }
89        output
90    }
91
92    fn inverse(&self, coeffs: &[f64]) -> Vec<f64> {
93        let mut output = coeffs.to_vec();
94        let mut length = 2;
95
96        // Iteratively reconstruct from coarsest to finest level
97        while length <= output.len() {
98            let mut temp = vec![0.0; length];
99            for i in 0..length / 2 {
100                // Reconstruct original values from average and detail coefficients.
101                let average = output[i];
102                let difference = output[length / 2 + i];
103                temp[2 * i] = average + difference; // First reconstructed value
104                temp[2 * i + 1] = average - difference; // Second reconstructed value
105            }
106            // Copy reconstructed values back to output for the next finer level.
107            output[..length].clone_from_slice(&temp);
108            length *= 2; // Expand length to work on the next finer level
109        }
110        output
111    }
112}
devela/phys/wave/alloc.rs

devela/phys/wave/
alloc.rs
