qoi/src/encode.rs

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use std::convert::TryInto;
use crate::colorspace::ColorSpace;
use crate::consts::{
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QOI_HEADER_SIZE, QOI_OP_INDEX, 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};
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use crate::utils::{unlikely, BytesMut};
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#[allow(clippy::cast_possible_truncation)]
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fn qoi_encode_impl<const N: usize>(
out: &mut [u8], data: &[u8], width: u32, height: u32, colorspace: ColorSpace,
) -> Result<usize>
where
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Pixel<N>: SupportedChannels,
{
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let max_len = encode_size_required(width, height, N 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 * N != data.len()) {
return Err(Error::BadEncodingDataSize { size: data.len(), expected: n_pixels * N });
}
let out_size = out.len();
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let mut buf = BytesMut::new(out);
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let header = Header { width, height, channels: N as u8, colorspace };
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buf = buf.write_many(&header.encode());
let mut index = [Pixel::new(); 256];
let mut px_prev = Pixel::new().with_a(0xff);
let mut run = 0_u8;
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let mut px = Pixel::<N>::new().with_a(0xff);
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for (i, chunk) in data.chunks_exact(N).enumerate() {
px.read(chunk);
if px == px_prev {
run += 1;
if run == 62 || unlikely(i == n_pixels - 1) {
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buf = buf.write_one(QOI_OP_RUN | (run - 1));
run = 0;
}
} else {
if run != 0 {
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buf = buf.write_one(QOI_OP_RUN | (run - 1));
run = 0;
}
let index_pos = px.hash_index();
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let index_px = &mut index[index_pos as usize];
let px_rgba = px.as_rgba(0xff);
if *index_px == px_rgba {
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buf = buf.write_one(QOI_OP_INDEX | index_pos);
} else {
*index_px = px_rgba;
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buf = px.encode_into(px_prev, buf);
}
px_prev = px;
}
}
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buf = buf.write_many(&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
}