.github/workflows/ci.yml

@@ -13,7 +13,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        rust: [stable, beta, nightly, 1.61.0]  # MSRV=1.61
+        rust: [stable, beta, nightly, 1.51.0]  # MSRV=1.51
     steps:
       - uses: actions/checkout@v2
         with: {submodules: true}

Cargo.toml

@@ -1,9 +1,9 @@
 [package]
 name = "qoi"
-version = "0.4.1"
+version = "0.4.0"
 description = "VERY fast encoder/decoder for QOI (Quite Okay Image) format"
 authors = ["Ivan Smirnov <rust@ivan.smirnov.ie>"]
-edition = "2021"
+edition = "2018"
 readme = "README.md"
 license = "MIT/Apache-2.0"
 repository = "https://github.com/aldanor/qoi-rust"
@@ -14,7 +14,7 @@ keywords = ["qoi", "graphics", "image", "encoding"]
 exclude = [
     "assets/*",
 ]
-rust-version = "1.61.0"
+rust-version = "1.51.0"
 
 [features]
 default = ["std"]
@@ -23,7 +23,7 @@ std = []        # std mode (enabled by default) - provides access to `std::io`,
 reference = []  # follows reference encoder implementation precisely, but may be slightly slower
 
 [dependencies]
-bytemuck = "1.12"
+bytemuck = "1.7"
 
 [workspace]
 members = ["libqoi", "bench"]

README.md

@@ -16,16 +16,6 @@ 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
@@ -61,7 +51,8 @@ this library proved to be the fastest one by a noticeable margin.
 
 ### Rust version
 
-The minimum required Rust version for the latest crate version is 1.61.0.
+The minimum required Rust version is 1.51.0 (any changes to this would be
+considered to be a breaking change).
 
 ### `no_std`
 

src/consts.rs

@@ -4,7 +4,6 @@ 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
 

src/decode.rs

@@ -49,21 +49,9 @@ where
                 px.update_rgb(*r, *g, *b);
                 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;
-                }
+            [QOI_OP_RGBA, r, g, b, a, dtail @ ..] if RGBA => {
+                px.update_rgba(*r, *g, *b, *a);
+                data = dtail;
             }
             [b1 @ QOI_OP_RUN..=QOI_OP_RUN_END, dtail @ ..] => {
                 *px_out = px.into();

src/encode.rs

@@ -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, QOI_OP_RUN2};
+use crate::consts::{QOI_HEADER_SIZE, QOI_OP_INDEX, QOI_OP_RUN, QOI_PADDING, QOI_PADDING_SIZE};
 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_u16;
+    let mut run = 0_u8;
     let mut px = Pixel::<N>::new().with_a(0xff);
     let mut index_allowed = false;
 
@@ -36,20 +36,8 @@ 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 as u8 - 1))?;
+                buf = buf.write_one(QOI_OP_RUN | (run - 1))?;
                 run = 0;
             }
         } else {
@@ -57,18 +45,15 @@ where
                 #[cfg(not(feature = "reference"))]
                 {
                     // credits for the original idea: @zakarumych (had to be fixed though)
-                    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))?
+                    buf = buf.write_one(if run == 1 && index_allowed {
+                        QOI_OP_INDEX | hash_prev
                     } else {
-                        let [b1, b2] = (run-1).to_be_bytes();
-                        buf.write_many(&[QOI_OP_RUN2, b1, b2])?
-                    };
+                        QOI_OP_RUN | (run - 1)
+                    })?;
                 }
                 #[cfg(feature = "reference")]
                 {
-                    buf = buf.write_one(QOI_OP_RUN | (run as u8 - 1))?;
+                    buf = buf.write_one(QOI_OP_RUN | (run - 1))?;
                 }
                 run = 0;
             }