This commit is contained in:
ZettaScript 2022-12-16 22:12:43 +01:00
parent e97077e527
commit 8099e065f3
4 changed files with 49 additions and 11 deletions

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@ -16,6 +16,16 @@ Fast encoder/decoder for [QOI image format](https://qoiformat.org/), implemented
- `no_std` support.
- Roundtrip-tested vs the reference C implementation; fuzz-tested.
### Note about this fork
This fork implements a slight improvement to the original specs, which leaves unused the `QOI_OP_RGBA` chunk flag with RGB.
Here, we use this flag for the new `QOI_OP_RUN2` chunk. It's like the `QOI_OP_RUN` chunk, but followed by two bytes representing `run` (BE). (only for RGB, as the flag is already used for RGBA)
The decoder remains fully compatible with the original one (except when using `QOI_OP_RGBA` in a RGB image). The encoder is fully compatible for RGBA, not for RGB (except using the `reference` feature).
Why this? Because it enables significant improvements for compressing images with large uniform areas (such as screen captures), or for encoding a diff-filtered video stream where successive frames often have identical regions. (see [syeve](https://framagit.org/ZettaScript/syeve) for the video encoding)
### Examples
```rust

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@ -4,6 +4,7 @@ pub const QOI_OP_LUMA: u8 = 0x80; // 10xxxxxx
pub const QOI_OP_RUN: u8 = 0xc0; // 11xxxxxx
pub const QOI_OP_RGB: u8 = 0xfe; // 11111110
pub const QOI_OP_RGBA: u8 = 0xff; // 11111111
pub const QOI_OP_RUN2: u8 = 0xff; // 11111111
pub const QOI_MASK_2: u8 = 0xc0; // (11)000000

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@ -49,9 +49,21 @@ where
px.update_rgb(*r, *g, *b);
data = dtail;
}
[QOI_OP_RGBA, r, g, b, a, dtail @ ..] if RGBA => {
px.update_rgba(*r, *g, *b, *a);
data = dtail;
[QOI_OP_RGBA, dtail @ ..] => {
if RGBA {
if let [r, g, b, a, dtail @ ..] = dtail {
px.update_rgba(*r, *g, *b, *a);
data = dtail;
}
} else if let [b1, b2, dtail @ ..] = dtail {
*px_out = px.into();
let run = (u16::from_be_bytes([*b1, *b2]) as usize).min(pixels.len());
let (phead, ptail) = pixels.split_at_mut(run); // can't panic
phead.fill(px.into());
pixels = ptail;
data = dtail;
continue;
}
}
[b1 @ QOI_OP_RUN..=QOI_OP_RUN_END, dtail @ ..] => {
*px_out = px.into();

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@ -6,7 +6,7 @@ use std::io::Write;
use bytemuck::Pod;
use crate::consts::{QOI_HEADER_SIZE, QOI_OP_INDEX, QOI_OP_RUN, QOI_PADDING, QOI_PADDING_SIZE};
use crate::consts::{QOI_HEADER_SIZE, QOI_OP_INDEX, QOI_OP_RUN, QOI_PADDING, QOI_PADDING_SIZE, QOI_OP_RUN2};
use crate::error::{Error, Result};
use crate::header::Header;
use crate::pixel::{Pixel, SupportedChannels};
@ -26,7 +26,7 @@ where
let mut index = [Pixel::new(); 256];
let mut px_prev = Pixel::new().with_a(0xff);
let mut hash_prev = px_prev.hash_index();
let mut run = 0_u8;
let mut run = 0_u16;
let mut px = Pixel::<N>::new().with_a(0xff);
let mut index_allowed = false;
@ -36,8 +36,20 @@ where
px.read(chunk);
if px == px_prev {
run += 1;
#[cfg(not(feature = "reference"))]
if N == 3 {
if run == 65535 || unlikely(i == n_pixels - 1) {
let [b1, b2] = (run-1).to_be_bytes();
buf = buf.write_many(&[QOI_OP_RUN2, b1, b2])?;
run = 0;
}
} else if run == 62 || unlikely(i == n_pixels - 1) {
buf = buf.write_one(QOI_OP_RUN | (run as u8 - 1))?;
run = 0;
}
#[cfg(feature = "reference")]
if run == 62 || unlikely(i == n_pixels - 1) {
buf = buf.write_one(QOI_OP_RUN | (run - 1))?;
buf = buf.write_one(QOI_OP_RUN | (run as u8 - 1))?;
run = 0;
}
} else {
@ -45,15 +57,18 @@ where
#[cfg(not(feature = "reference"))]
{
// credits for the original idea: @zakarumych (had to be fixed though)
buf = buf.write_one(if run == 1 && index_allowed {
QOI_OP_INDEX | hash_prev
buf = if run == 1 && index_allowed {
buf.write_one(QOI_OP_INDEX | hash_prev)?
} else if N == 4 || run < 63 {
buf.write_one(QOI_OP_RUN | (run as u8 - 1))?
} else {
QOI_OP_RUN | (run - 1)
})?;
let [b1, b2] = (run-1).to_be_bytes();
buf.write_many(&[QOI_OP_RUN2, b1, b2])?
};
}
#[cfg(feature = "reference")]
{
buf = buf.write_one(QOI_OP_RUN | (run - 1))?;
buf = buf.write_one(QOI_OP_RUN | (run as u8 - 1))?;
}
run = 0;
}