implement basic accuracy testing binary

Author: FreezyLemon

Cargo.toml

@@ -13,6 +13,7 @@ exclude = ["test_data", "yuvxyb-dump"]
 [features]
 default = ["fastmath"]
 fastmath = []
+build-acctest = ["image", "plotters"]
 
 [dependencies]
 av-data = "0.4.1"
@@ -23,12 +24,20 @@ paste = "1.0.9"
 thiserror = "1.0.40"
 v_frame = "0.3.0"
 
+# acctest dependencies
+image = { version = "0.24.5", optional = true }
+plotters = { version = "0.3.1", optional = true }
+
 [dev-dependencies]
 criterion = "0.4.0"
-image = "0.24.4"
+image = "0.24.5"
 interpolate_name = "0.2.3"
 rand = "0.8.5"
 
 [[bench]]
 name = "benches"
 harness = false
+
+[[bin]]
+name = "acctest"
+required-features = ["build-acctest"]

src/bin/acctest.rs

@@ -0,0 +1,107 @@
+use std::path::PathBuf;
+use std::ops::{Range, Neg};
+
+use anyhow::Result;
+use yuvxyb::{LinearRgb, TransferCharacteristic, ColorPrimaries, Rgb};
+
+fn main() {
+    compare("tank_srgb.png", "tank_rgb.png", "tank_comparison.png");
+    compare("chimera_srgb.png", "chimera_rgb.png", "chimera_comparison.png");
+    compare("chimera_srgb.png", "tank_rgb.png", "useless_comparison.png");
+}
+
+fn compare(source_path: &str, expected_path: &str, graph_path: &str) {
+    let source = struct_from_file(source_path, |d, w, h| Rgb::new(d, w, h, TransferCharacteristic::SRGB, ColorPrimaries::BT709)).unwrap();
+    let expected = struct_from_file(expected_path, LinearRgb::new).unwrap();
+
+    let actual = LinearRgb::try_from(source).unwrap();
+
+    let deltas = compare_data(expected.data(), actual.data());
+    draw_graph(deltas, ["R".to_string(), "G".to_string(), "B".to_string()], graph_path);
+}
+
+fn struct_from_file<T>(path: &str, create_fn: fn(Vec<[f32; 3]>, usize, usize) -> Result<T>) -> Result<T> {
+    let base_path = PathBuf::from(env!("CARGO_MANIFEST_DIR")).join("test_data");
+    let img = image::open(base_path.join(path)).unwrap();
+
+    let w = img.width() as usize;
+    let h = img.height() as usize;
+    let data: Vec<[f32; 3]> = img
+        .into_rgb32f()
+        .chunks_exact(3)
+        .map(|c| [c[0], c[1], c[2]])
+        .collect();
+
+    create_fn(data, w, h)
+}
+
+// return the delta for each channel/plane
+fn compare_data(expected: &[[f32; 3]], actual: &[[f32; 3]]) -> [Vec<f32>; 3] {
+    let mut r = vec![0f32; expected.len()];
+    let mut g = vec![0f32; expected.len()];
+    let mut b = vec![0f32; expected.len()];
+
+    for (i, (pix_e, pix_a)) in expected.iter().zip(actual).enumerate() {
+        r[i] = pix_a[0] - pix_e[0];
+        g[i] = pix_a[1] - pix_e[1];
+        b[i] = pix_a[2] - pix_e[2];
+    }
+
+    [r, g, b]
+}
+
+fn draw_graph(deltas: [Vec<f32>; 3], plane_labels: [String; 3], path: &str) {
+    use plotters::prelude::*;
+    use plotters::data::fitting_range;
+
+    let root = BitMapBackend::new(path, (640, 360)).into_drawing_area();
+    root.fill(&WHITE).unwrap();
+    let root = root.margin(5, 5, 5, 20); // leave some space on the right
+
+    let dataset: Vec<(String, Quartiles)> = deltas.iter().zip(&plane_labels).map(|(v, l)| (l.clone(), Quartiles::new(&v))).collect();
+    let range = fitting_range(deltas.iter().flatten());
+    let range = refit_range(range);
+
+    let mut cc = ChartBuilder::on(&root)
+        .x_label_area_size(50)
+        .y_label_area_size(25)
+        .caption("Conversion errors per color plane", ("sans-serif", 20))
+        .build_cartesian_2d(
+            // -5e-3f32..5e-3f32,
+            range,
+            plane_labels.into_segmented(),
+        )
+        .unwrap();
+
+    cc.configure_mesh()
+        .x_desc("Error")
+        .x_label_style(("sans-serif", 20))
+        .y_labels(plane_labels.len())
+        .y_label_style(("sans-serif", 20))
+        .y_label_formatter(&|v| match v {
+            SegmentValue::Exact(l) => l.to_string(),
+            SegmentValue::CenterOf(l) => l.to_string(),
+            SegmentValue::Last => String::new(),
+        })
+        .light_line_style(&WHITE)
+        .draw()
+        .unwrap();
+
+    cc.draw_series(dataset.iter().map(|(l, q)| {
+            Boxplot::new_horizontal(SegmentValue::CenterOf(l), q)
+                .width(25)
+                .whisker_width(0.5)
+        }))
+        .unwrap();
+
+    root.present().unwrap();
+}
+
+// make "symmetric"/centered around zero
+fn refit_range<T: Neg<Output = T> + PartialOrd + Copy>(r: Range<T>) -> Range<T> {
+    if r.end > -r.start {
+        -r.end..r.end
+    } else {
+        r.start..-r.start
+    }
+}