Add reference check tests

Cargo.toml

@@ -19,7 +19,9 @@ exclude = [
 members = ["qoi-bench"]
 
 [dev-dependencies]
-png = "^0.17.2"
+anyhow = "1.0"
+png = "0.17"
+walkdir = "2.3"
 
 [lib]
 name = "qoi_fast"

tests/test_ref.rs

@@ -0,0 +1,106 @@
+use std::fs::{self, File};
+use std::path::{Path, PathBuf};
+
+use anyhow::{bail, Result};
+use walkdir::{DirEntry, WalkDir};
+
+use qoi_fast::{qoi_decode_to_vec, qoi_encode_to_vec};
+
+fn find_qoi_png_pairs(root: impl AsRef<Path>) -> Vec<(PathBuf, PathBuf)> {
+    let root = root.as_ref();
+
+    let get_ext =
+        |path: &Path| path.extension().unwrap_or_default().to_string_lossy().to_ascii_lowercase();
+    let check_qoi_png_pair = |path: &Path| {
+        let (qoi, png) = (path.to_path_buf(), path.with_extension("png"));
+        if qoi.is_file() && get_ext(&qoi) == "qoi" && png.is_file() {
+            Some((qoi, png))
+        } else {
+            None
+        }
+    };
+
+    let mut out = vec![];
+    if let Some(pair) = check_qoi_png_pair(root) {
+        out.push(pair);
+    } else if root.is_dir() {
+        out.extend(
+            WalkDir::new(root)
+                .follow_links(true)
+                .into_iter()
+                .filter_map(Result::ok)
+                .map(DirEntry::into_path)
+                .filter_map(|p| check_qoi_png_pair(&p)),
+        )
+    }
+    out
+}
+
+struct Image {
+    pub width: u32,
+    pub height: u32,
+    pub channels: u8,
+    pub data: Vec<u8>,
+}
+
+impl Image {
+    fn from_png(filename: &Path) -> Result<Self> {
+        let decoder = png::Decoder::new(File::open(filename)?);
+        let mut reader = decoder.read_info()?;
+        let mut buf = vec![0; reader.output_buffer_size()];
+        let info = reader.next_frame(&mut buf)?;
+        let bytes = &buf[..info.buffer_size()];
+        Ok(Self {
+            width: info.width,
+            height: info.height,
+            channels: info.color_type.samples() as u8,
+            data: bytes.to_vec(),
+        })
+    }
+}
+
+fn compare_slices(name: &str, desc: &str, result: &[u8], expected: &[u8]) -> Result<()> {
+    if result == expected {
+        Ok(())
+    } else {
+        if let Some(i) =
+            (0..result.len().min(expected.len())).position(|i| result[i] != expected[i])
+        {
+            bail!(
+                "{}: {} mismatch at byte {}: expected {:?}, got {:?}",
+                name,
+                desc,
+                i,
+                &expected[i..(i + 4).min(expected.len())],
+                &result[i..(i + 4).min(result.len())],
+            );
+        } else {
+            bail!(
+                "{}: {} length mismatch: expected {}, got {}",
+                name,
+                desc,
+                expected.len(),
+                result.len()
+            );
+        }
+    }
+}
+
+#[test]
+fn test_reference_images() -> Result<()> {
+    let pairs = find_qoi_png_pairs("assets");
+    assert!(!pairs.is_empty());
+
+    for (qoi_path, png_path) in &pairs {
+        let png_name = png_path.file_name().unwrap_or_default().to_string_lossy();
+        let img = Image::from_png(png_path)?;
+        println!("{} {} {} {}", png_name, img.width, img.height, img.channels);
+        let encoded = qoi_encode_to_vec(&img.data, img.width, img.height, img.channels, 0)?;
+        let expected = fs::read(qoi_path)?;
+        compare_slices(&png_name, "encoding", &encoded, &expected)?;
+        let (_header, decoded) = qoi_decode_to_vec(&expected, img.channels)?;
+        compare_slices(&png_name, "decoding", &decoded, &img.data)?;
+    }
+
+    Ok(())
+}