qoi/
pixel.rs

1use crate::consts::{QOI_OP_DIFF, QOI_OP_LUMA, QOI_OP_RGB, QOI_OP_RGBA};
2use crate::error::Result;
3use crate::utils::Writer;
4use bytemuck::{cast, Pod};
5
6#[derive(Copy, Clone, PartialEq, Eq, Debug)]
7#[repr(transparent)]
8pub struct Pixel<const N: usize>([u8; N]);
9
10impl<const N: usize> Pixel<N> {
11    #[inline]
12    pub const fn new() -> Self {
13        Self([0; N])
14    }
15
16    #[inline]
17    pub fn read(&mut self, s: &[u8]) {
18        if s.len() == N {
19            let mut i = 0;
20            while i < N {
21                self.0[i] = s[i];
22                i += 1;
23            }
24        } else {
25            unreachable!();
26        }
27    }
28
29    #[inline]
30    pub fn update<const M: usize>(&mut self, px: Pixel<M>) {
31        let mut i = 0;
32        while i < M && i < N {
33            self.0[i] = px.0[i];
34            i += 1;
35        }
36    }
37
38    #[inline]
39    pub fn update_rgb(&mut self, r: u8, g: u8, b: u8) {
40        self.0[0] = r;
41        self.0[1] = g;
42        self.0[2] = b;
43    }
44
45    #[inline]
46    pub fn update_rgba(&mut self, r: u8, g: u8, b: u8, a: u8) {
47        self.0[0] = r;
48        self.0[1] = g;
49        self.0[2] = b;
50        if N >= 4 {
51            self.0[3] = a;
52        }
53    }
54
55    #[inline]
56    pub fn update_diff(&mut self, b1: u8) {
57        self.0[0] = self.0[0].wrapping_add((b1 >> 4) & 0x03).wrapping_sub(2);
58        self.0[1] = self.0[1].wrapping_add((b1 >> 2) & 0x03).wrapping_sub(2);
59        self.0[2] = self.0[2].wrapping_add(b1 & 0x03).wrapping_sub(2);
60    }
61
62    #[inline]
63    pub fn update_luma(&mut self, b1: u8, b2: u8) {
64        let vg = (b1 & 0x3f).wrapping_sub(32);
65        let vg_8 = vg.wrapping_sub(8);
66        let vr = vg_8.wrapping_add((b2 >> 4) & 0x0f);
67        let vb = vg_8.wrapping_add(b2 & 0x0f);
68        self.0[0] = self.0[0].wrapping_add(vr);
69        self.0[1] = self.0[1].wrapping_add(vg);
70        self.0[2] = self.0[2].wrapping_add(vb);
71    }
72
73    #[inline]
74    pub const fn as_rgba(self, with_a: u8) -> Pixel<4> {
75        let mut i = 0;
76        let mut out = Pixel::new();
77        while i < N {
78            out.0[i] = self.0[i];
79            i += 1;
80        }
81        if N < 4 {
82            out.0[3] = with_a;
83        }
84        out
85    }
86
87    #[inline]
88    pub const fn r(self) -> u8 {
89        self.0[0]
90    }
91
92    #[inline]
93    pub const fn g(self) -> u8 {
94        self.0[1]
95    }
96
97    #[inline]
98    pub const fn b(self) -> u8 {
99        self.0[2]
100    }
101
102    #[inline]
103    pub const fn with_a(mut self, value: u8) -> Self {
104        if N >= 4 {
105            self.0[3] = value;
106        }
107        self
108    }
109
110    #[inline]
111    pub const fn a_or(self, value: u8) -> u8 {
112        if N < 4 {
113            value
114        } else {
115            self.0[3]
116        }
117    }
118
119    #[inline]
120    #[allow(clippy::cast_lossless, clippy::cast_possible_truncation)]
121    pub fn hash_index(self) -> u8
122    where
123        [u8; N]: Pod,
124    {
125        // credits for the initial idea: @zakarumych
126        let v = if N == 4 {
127            u32::from_ne_bytes(cast(self.0))
128        } else {
129            u32::from_ne_bytes([self.0[0], self.0[1], self.0[2], 0xff])
130        } as u64;
131        let s = ((v & 0xff00_ff00) << 32) | (v & 0x00ff_00ff);
132        s.wrapping_mul(0x0300_0700_0005_000b_u64).to_le().swap_bytes() as u8 & 63
133    }
134
135    #[inline]
136    pub fn rgb_add(&mut self, r: u8, g: u8, b: u8) {
137        self.0[0] = self.0[0].wrapping_add(r);
138        self.0[1] = self.0[1].wrapping_add(g);
139        self.0[2] = self.0[2].wrapping_add(b);
140    }
141
142    #[inline]
143    pub fn encode_into<W: Writer>(&self, px_prev: Self, buf: W) -> Result<W> {
144        if N == 3 || self.a_or(0) == px_prev.a_or(0) {
145            let vg = self.g().wrapping_sub(px_prev.g());
146            let vg_32 = vg.wrapping_add(32);
147            if vg_32 | 63 == 63 {
148                let vr = self.r().wrapping_sub(px_prev.r());
149                let vb = self.b().wrapping_sub(px_prev.b());
150                let vg_r = vr.wrapping_sub(vg);
151                let vg_b = vb.wrapping_sub(vg);
152                let (vr_2, vg_2, vb_2) =
153                    (vr.wrapping_add(2), vg.wrapping_add(2), vb.wrapping_add(2));
154                if vr_2 | vg_2 | vb_2 | 3 == 3 {
155                    buf.write_one(QOI_OP_DIFF | vr_2 << 4 | vg_2 << 2 | vb_2)
156                } else {
157                    let (vg_r_8, vg_b_8) = (vg_r.wrapping_add(8), vg_b.wrapping_add(8));
158                    if vg_r_8 | vg_b_8 | 15 == 15 {
159                        buf.write_many(&[QOI_OP_LUMA | vg_32, vg_r_8 << 4 | vg_b_8])
160                    } else {
161                        buf.write_many(&[QOI_OP_RGB, self.r(), self.g(), self.b()])
162                    }
163                }
164            } else {
165                buf.write_many(&[QOI_OP_RGB, self.r(), self.g(), self.b()])
166            }
167        } else {
168            buf.write_many(&[QOI_OP_RGBA, self.r(), self.g(), self.b(), self.a_or(0xff)])
169        }
170    }
171}
172
173impl<const N: usize> From<Pixel<N>> for [u8; N] {
174    #[inline(always)]
175    fn from(px: Pixel<N>) -> Self {
176        px.0
177    }
178}
179
180pub trait SupportedChannels {}
181
182impl SupportedChannels for Pixel<3> {}
183impl SupportedChannels for Pixel<4> {}
qoi/pixel.rs

qoi/
pixel.rs
