jixel 0.2.4

Tiny JPEG XL encoder
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
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130

/*
 * // Copyright (c) Radzivon Bartoshyk 6/2026. All rights reserved.
 * //
 * // Redistribution and use in source and binary forms, with or without modification,
 * // are permitted provided that the following conditions are met:
 * //
 * // 1.  Redistributions of source code must retain the above copyright notice, this
 * // list of conditions and the following disclaimer.
 * //
 * // 2.  Redistributions in binary form must reproduce the above copyright notice,
 * // this list of conditions and the following disclaimer in the documentation
 * // and/or other materials provided with the distribution.
 * //
 * // 3.  Neither the name of the copyright holder nor the names of its
 * // contributors may be used to endorse or promote products derived from
 * // this software without specific prior written permission.
 * //
 * // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * // AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * // IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * // DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 * // FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * // DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * // SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * // CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * // OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#[cfg(target_arch = "x86")]
use std::arch::x86::*;
#[cfg(target_arch = "x86_64")]
use std::arch::x86_64::*;

#[inline]
#[target_feature(enable = "sse4.1")]
fn hsum(v: __m128) -> f32 {
    let shuf = _mm_movehdup_ps(v); // [1,1,3,3]
    let sums = _mm_add_ps(v, shuf);
    let shuf2 = _mm_movehl_ps(shuf, sums);
    let sums = _mm_add_ss(sums, shuf2);
    _mm_cvtss_f32(sums)
}

/// SSE4.1 implementation of `sse_and_rate_scalar`.
///
/// # Safety
/// Caller must ensure `sse4.1` is available (checked via [`supported`]). All
/// slice accesses are bounds-validated against `width*height`.
#[allow(clippy::too_many_arguments)]
#[target_feature(enable = "sse4.1")]
pub(crate) fn sse_and_rate_sse(
    coeff: &[f32],
    inv_matrix: &[f32],
    q_scaled: f32,
    width: usize,
    height: usize,
    half: usize,
    cx: usize,
    cy: usize,
    thr: &[f32; 4],
) -> (f32, usize, f32) {
    let n = width * height;
    assert!(coeff.len() >= n && inv_matrix.len() >= n);
    debug_assert!(width.is_multiple_of(4) && half.is_multiple_of(4));

    let qs = _mm_set1_ps(q_scaled);
    let mut sse_acc = _mm_setzero_ps();
    let mut nzeros = 0usize;
    let mut mag_bits = 0.0f32;

    // round-to-nearest-even via SSE4.1
    const RND: i32 = _MM_FROUND_TO_NEAREST_INT | _MM_FROUND_NO_EXC;

    let mut qbuf = [0.0f32; 4];

    for y in 0..height {
        let yfix = if y >= height / 2 { 2 } else { 0 };
        let thr_lo = thr[yfix];
        let thr_hi = thr[yfix + 1];
        let row = y * width;
        let mut x = 0;
        while x < width {
            let threshold = if x >= half { thr_hi } else { thr_lo };
            let thrv = _mm_set1_ps(threshold);
            let idx = row + x;
            let cv = unsafe { _mm_loadu_ps(coeff[idx..idx + 4].as_ptr()) };
            let mv = unsafe { _mm_loadu_ps(inv_matrix[idx..idx + 4].as_ptr()) };
            // a = inv_matrix * q_scaled * coeff
            let a = _mm_mul_ps(_mm_mul_ps(mv, qs), cv);
            let absa = _mm_andnot_ps(_mm_set1_ps(-0.0), a);
            // keep = |a| >= threshold
            let keep = _mm_cmpge_ps(absa, thrv);
            let rounded = _mm_round_ps::<RND>(a);
            let q = _mm_and_ps(rounded, keep); // zero where not kept
            let d = _mm_sub_ps(a, q);
            let mut d2 = _mm_mul_ps(d, d);

            // Mask out LLF lanes (x'<cx && y<cy) so they contribute nothing.
            if y < cy && x == 0 {
                // lanes 0..cx are LLF → 0.0; all other lanes kept → 1.0
                let mut lanemask = [1.0f32; 4];

                for lane in 0..cx.min(4) {
                    lanemask[lane] = 0.0;
                }
                let lm = unsafe { _mm_loadu_ps(lanemask.as_ptr()) };
                d2 = _mm_mul_ps(d2, lm); // zero LLF squared-errors
            }
            sse_acc = _mm_add_ps(sse_acc, d2);

            // Rate: count nonzeros and accumulate log2(1+|q|) from kept lanes.
            unsafe {
                _mm_storeu_ps(qbuf.as_mut_ptr(), q);
            }
            for lane in 0..4 {
                if y < cy && x == 0 && lane < cx {
                    continue; // LLF
                }
                let qv = qbuf[lane];
                if qv != 0.0 {
                    nzeros += 1;
                    mag_bits += crate::enc_ac_strategy::rate_log2(qv.abs());
                }
            }
            x += 4;
        }
    }
    (hsum(sse_acc), nzeros, mag_bits)
}