qoi/src/encode.rs

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use std::convert::TryInto;
use crate::colorspace::ColorSpace;
use crate::consts::{
QOI_HEADER_SIZE, QOI_OP_DIFF, QOI_OP_INDEX, QOI_OP_LUMA, QOI_OP_RGB, QOI_OP_RGBA, QOI_OP_RUN,
QOI_PADDING, QOI_PADDING_SIZE, QOI_PIXELS_MAX,
};
use crate::error::{Error, Result};
use crate::header::Header;
use crate::pixel::{Pixel, SupportedChannels};
use crate::utils::{cold, unlikely};
struct WriteBuf<'a> {
buf: &'a mut [u8],
}
impl<'a> WriteBuf<'a> {
pub fn new(buf: &'a mut [u8]) -> Self {
Self { buf }
}
#[inline]
pub fn write<const N: usize>(self, v: [u8; N]) -> Self {
let (head, tail) = self.buf.split_at_mut(N);
head.copy_from_slice(&v);
Self { buf: tail }
}
#[inline]
pub fn push(self, v: u8) -> Self {
if let Some((first, tail)) = self.buf.split_first_mut() {
*first = v;
Self { buf: tail }
} else {
cold();
panic!();
}
}
#[inline]
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pub const fn len(&self) -> usize {
self.buf.len()
}
}
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#[allow(clippy::cast_possible_truncation)]
fn qoi_encode_impl<const CHANNELS: usize>(
out: &mut [u8], data: &[u8], width: u32, height: u32, colorspace: ColorSpace,
) -> Result<usize>
where
Pixel<CHANNELS>: SupportedChannels,
{
let max_len = encode_size_required(width, height, CHANNELS as u8);
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if unlikely(out.len() < max_len) {
return Err(Error::OutputBufferTooSmall { size: out.len(), required: max_len });
}
let n_pixels = (width as usize) * (height as usize);
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if unlikely(data.is_empty()) {
return Err(Error::EmptyImage { width, height });
} else if unlikely(n_pixels > QOI_PIXELS_MAX) {
return Err(Error::ImageTooLarge { width, height });
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} else if unlikely(n_pixels * CHANNELS != data.len()) {
return Err(Error::BadEncodingDataSize { size: data.len(), expected: n_pixels * CHANNELS });
}
let out_size = out.len();
let mut buf = WriteBuf::new(out);
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let header =
Header { width, height, channels: CHANNELS as u8, colorspace, ..Header::default() };
buf = buf.write(header.encode());
let mut index = [Pixel::new(); 256];
let mut px_prev = Pixel::new().with_a(0xff);
let mut run = 0_u8;
let mut px = Pixel::<CHANNELS>::new().with_a(0xff);
for (i, chunk) in data.chunks_exact(CHANNELS).enumerate() {
px.read(chunk);
if px == px_prev {
run += 1;
if run == 62 || unlikely(i == n_pixels - 1) {
buf = buf.push(QOI_OP_RUN | (run - 1));
run = 0;
}
} else {
if run != 0 {
buf = buf.push(QOI_OP_RUN | (run - 1));
run = 0;
}
let index_pos = px.hash_index();
let index_px = &mut index[usize::from(index_pos)];
let px_rgba = px.as_rgba(0xff);
if *index_px == px_rgba {
buf = buf.push(QOI_OP_INDEX | index_pos);
} else {
*index_px = px_rgba;
if px.a_or(0) == px_prev.a_or(0) {
let vr = px.r().wrapping_sub(px_prev.r());
let vg = px.g().wrapping_sub(px_prev.g());
let vb = px.b().wrapping_sub(px_prev.b());
let vg_r = vr.wrapping_sub(vg);
let vg_b = vb.wrapping_sub(vg);
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let vg_32 = vg.wrapping_add(32);
if vg_32 | 63 == 63 {
let (vr_2, vg_2, vb_2) =
(vr.wrapping_add(2), vg.wrapping_add(2), vb.wrapping_add(2));
if vr_2 | vg_2 | vb_2 | 3 == 3 {
buf = buf.push(QOI_OP_DIFF | vr_2 << 4 | vg_2 << 2 | vb_2);
} else {
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let (vg_r_8, vg_b_8) = (vg_r.wrapping_add(8), vg_b.wrapping_add(8));
if vg_r_8 | vg_b_8 | 15 == 15 {
buf = buf.write([QOI_OP_LUMA | vg_32, vg_r_8 << 4 | vg_b_8]);
} else {
buf = buf.write([QOI_OP_RGB, px.r(), px.g(), px.b()]);
}
}
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} else {
buf = buf.write([QOI_OP_RGB, px.r(), px.g(), px.b()]);
}
} else {
buf = buf.write([QOI_OP_RGBA, px.r(), px.g(), px.b(), px.a_or(0xff)]);
}
}
px_prev = px;
}
}
buf = buf.write(QOI_PADDING);
Ok(out_size.saturating_sub(buf.len()))
}
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#[inline]
pub fn qoi_encode_to_buf<O, D, C>(
mut out: O, data: D, width: u32, height: u32, channels: u8, colorspace: C,
) -> Result<usize>
where
O: AsMut<[u8]>,
D: AsRef<[u8]>,
C: TryInto<ColorSpace>,
Error: From<C::Error>,
{
let out = out.as_mut();
let data = data.as_ref();
let colorspace = colorspace.try_into()?;
match channels {
3 => qoi_encode_impl::<3>(out, data, width, height, colorspace),
4 => qoi_encode_impl::<4>(out, data, width, height, colorspace),
_ => Err(Error::InvalidChannels { channels }),
}
}
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#[inline]
pub fn qoi_encode_to_vec<D, C>(
data: D, width: u32, height: u32, channels: u8, colorspace: C,
) -> Result<Vec<u8>>
where
D: AsRef<[u8]>,
C: TryInto<ColorSpace>,
Error: From<C::Error>,
{
let size = encode_size_required(width, height, channels);
let mut out = vec![0; size]; // note: we could save time here but that won't be safe anymore
let size = qoi_encode_to_buf(&mut out, data, width, height, channels, colorspace)?;
out.truncate(size);
Ok(out)
}
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#[inline]
pub fn encode_size_required(width: u32, height: u32, channels: u8) -> usize {
let (width, height) = (width as usize, height as usize);
let n_pixels = width.saturating_mul(height);
QOI_HEADER_SIZE + n_pixels.saturating_mul(usize::from(channels)) + n_pixels + QOI_PADDING_SIZE
}