j2k-codec-math 0.11.0

no_std codec constants, generated fragments, and allocation-free helper algorithms for j2k
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90

//! JPEG 2000 discrete wavelet transform constants.

mod linearized53;
pub use linearized53::{
    linearized_dwt53_row, Dwt53Band, Dwt53LinearRow, Dwt53LinearTap, DWT53_MAX_HIGH_LINEAR_TAPS,
    DWT53_MAX_LINEAR_TAPS,
};

/// Return the maximum number of DWT decomposition levels supported by an
/// image geometry.
///
/// The shared encoder policy is `floor(log2(min(width, height)))`; a zero or
/// unit-length axis supports no decomposition levels.
#[must_use]
pub const fn max_decomposition_levels(width: u32, height: u32) -> u8 {
    j2k_types::encode_geometry::maximum_decomposition_levels(width, height)
}

/// Forward irreversible 9/7 lifting step alpha, rounded for existing CPU/GPU paths.
pub const DWT97_ALPHA_F32: f32 = -1.586_134_3;
/// Forward irreversible 9/7 lifting step beta, rounded for existing CPU/GPU paths.
pub const DWT97_BETA_F32: f32 = -0.052_980_117;
/// Forward irreversible 9/7 lifting step gamma, rounded for existing CPU/GPU paths.
pub const DWT97_GAMMA_F32: f32 = 0.882_911_1;
/// Forward irreversible 9/7 lifting step delta, rounded for existing CPU/GPU paths.
pub const DWT97_DELTA_F32: f32 = 0.443_506_87;
/// Irreversible 9/7 scaling factor, rounded for existing CPU/GPU paths.
pub const DWT97_KAPPA_F32: f32 = 1.230_174_1;
/// Inverse irreversible 9/7 scaling factor, computed the same way as existing paths.
pub const DWT97_INV_KAPPA_F32: f32 = 1.0 / DWT97_KAPPA_F32;
/// Historical high-pass synthesis scale used by `OpenJPEG`.
///
/// `OpenJPEG` pairs this value with uncompensated irreversible subband step
/// sizes.  The product is intentionally not identical to `2 / KAPPA`.
pub const IDWT97_OPENJPEG_TWO_INV_KAPPA_F32: f32 = 1.625_732_4;

/// Inverse 9/7 alpha step used by synthesis paths.
pub const IDWT97_NEG_ALPHA_F32: f32 = -DWT97_ALPHA_F32;
/// Inverse 9/7 beta step used by synthesis paths.
pub const IDWT97_NEG_BETA_F32: f32 = -DWT97_BETA_F32;
/// Inverse 9/7 gamma step used by synthesis paths.
pub const IDWT97_NEG_GAMMA_F32: f32 = -DWT97_GAMMA_F32;
/// Inverse 9/7 delta step used by synthesis paths.
pub const IDWT97_NEG_DELTA_F32: f32 = -DWT97_DELTA_F32;

/// Forward irreversible 9/7 lifting step alpha at f64 precision.
pub const DWT97_ALPHA_F64: f64 = -1.586_134_342_059_924;
/// Forward irreversible 9/7 lifting step beta at f64 precision.
pub const DWT97_BETA_F64: f64 = -0.052_980_118_572_961;
/// Forward irreversible 9/7 lifting step gamma at f64 precision.
pub const DWT97_GAMMA_F64: f64 = 0.882_911_075_530_934;
/// Forward irreversible 9/7 lifting step delta at f64 precision.
pub const DWT97_DELTA_F64: f64 = 0.443_506_852_043_971;
/// Irreversible 9/7 scaling factor at f64 precision.
pub const DWT97_KAPPA_F64: f64 = 1.230_174_104_914_001;
/// Inverse irreversible 9/7 scaling factor at f64 precision.
pub const DWT97_INV_KAPPA_F64: f64 = 1.0 / DWT97_KAPPA_F64;

#[cfg(test)]
mod tests {
    use super::*;

    const MAX_LEVELS_FOR_U32_GEOMETRY: u8 = max_decomposition_levels(u32::MAX, u32::MAX);

    #[test]
    fn maximum_decomposition_level_compatibility_export_is_const() {
        assert_eq!(MAX_LEVELS_FOR_U32_GEOMETRY, 31);
    }

    #[test]
    fn f32_constants_match_existing_backend_rounding() {
        assert_eq!(DWT97_ALPHA_F32.to_bits(), (-1.586_134_3f32).to_bits());
        assert_eq!(DWT97_BETA_F32.to_bits(), (-0.052_980_117f32).to_bits());
        assert_eq!(DWT97_GAMMA_F32.to_bits(), 0.882_911_1f32.to_bits());
        assert_eq!(DWT97_DELTA_F32.to_bits(), 0.443_506_87f32.to_bits());
        assert_eq!(DWT97_KAPPA_F32.to_bits(), 1.230_174_1f32.to_bits());
        assert_eq!(
            DWT97_INV_KAPPA_F32.to_bits(),
            (1.0f32 / 1.230_174_1f32).to_bits()
        );
    }

    #[test]
    fn inverse_constants_are_exact_negations_of_forward_steps() {
        assert_eq!(IDWT97_NEG_ALPHA_F32.to_bits(), (-DWT97_ALPHA_F32).to_bits());
        assert_eq!(IDWT97_NEG_BETA_F32.to_bits(), (-DWT97_BETA_F32).to_bits());
        assert_eq!(IDWT97_NEG_GAMMA_F32.to_bits(), (-DWT97_GAMMA_F32).to_bits());
        assert_eq!(IDWT97_NEG_DELTA_F32.to_bits(), (-DWT97_DELTA_F32).to_bits());
    }
}