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use image::{ImageBuffer, Rgba, RgbaImage};
use serde::Deserialize;
#[derive(Debug, Clone, Deserialize, Default)]
pub struct ManifestMeta {
pub width: Option<u32>,
pub height: Option<u32>,
pub lod: Option<usize>,
pub group: Option<usize>,
pub angle: Option<f32>,
pub diff_threshold: Option<u8>,
pub max_mean_abs: Option<f32>,
pub max_changed_ratio: Option<f32>,
}
#[derive(Debug, Clone, Deserialize)]
pub struct CaseSpec {
pub id: String,
pub archive: String,
pub model: Option<String>,
pub reference: String,
pub width: Option<u32>,
pub height: Option<u32>,
pub lod: Option<usize>,
pub group: Option<usize>,
pub angle: Option<f32>,
pub diff_threshold: Option<u8>,
pub max_mean_abs: Option<f32>,
pub max_changed_ratio: Option<f32>,
}
#[derive(Debug, Clone, Deserialize)]
pub struct ParityManifest {
#[serde(default)]
pub meta: ManifestMeta,
#[serde(rename = "case", default)]
pub cases: Vec<CaseSpec>,
}
#[derive(Debug, Clone)]
pub struct DiffMetrics {
pub width: u32,
pub height: u32,
pub mean_abs: f32,
pub max_abs: u8,
pub changed_pixels: u64,
pub changed_ratio: f32,
}
pub fn compare_images(
reference: &RgbaImage,
actual: &RgbaImage,
diff_threshold: u8,
) -> Result<DiffMetrics, String> {
let (rw, rh) = reference.dimensions();
let (aw, ah) = actual.dimensions();
if rw != aw || rh != ah {
return Err(format!(
"image size mismatch: reference={}x{}, actual={}x{}",
rw, rh, aw, ah
));
}
let mut diff_sum = 0u64;
let mut max_abs = 0u8;
let mut changed_pixels = 0u64;
let pixel_count = u64::from(rw).saturating_mul(u64::from(rh));
for (ref_px, act_px) in reference.pixels().zip(actual.pixels()) {
let mut pixel_changed = false;
for chan in 0..3 {
let a = i16::from(ref_px[chan]);
let b = i16::from(act_px[chan]);
let diff = (a - b).unsigned_abs() as u8;
diff_sum = diff_sum.saturating_add(u64::from(diff));
if diff > max_abs {
max_abs = diff;
}
if diff > diff_threshold {
pixel_changed = true;
}
}
if pixel_changed {
changed_pixels = changed_pixels.saturating_add(1);
}
}
let channels = pixel_count.saturating_mul(3);
let mean_abs = if channels == 0 {
0.0
} else {
diff_sum as f32 / channels as f32
};
let changed_ratio = if pixel_count == 0 {
0.0
} else {
changed_pixels as f32 / pixel_count as f32
};
Ok(DiffMetrics {
width: rw,
height: rh,
mean_abs,
max_abs,
changed_pixels,
changed_ratio,
})
}
pub fn build_diff_image(reference: &RgbaImage, actual: &RgbaImage) -> Result<RgbaImage, String> {
let (rw, rh) = reference.dimensions();
let (aw, ah) = actual.dimensions();
if rw != aw || rh != ah {
return Err(format!(
"image size mismatch: reference={}x{}, actual={}x{}",
rw, rh, aw, ah
));
}
let mut out: ImageBuffer<Rgba<u8>, Vec<u8>> = ImageBuffer::new(rw, rh);
for (dst, (ref_px, act_px)) in out
.pixels_mut()
.zip(reference.pixels().zip(actual.pixels()))
{
let dr = (i16::from(ref_px[0]) - i16::from(act_px[0])).unsigned_abs() as u8;
let dg = (i16::from(ref_px[1]) - i16::from(act_px[1])).unsigned_abs() as u8;
let db = (i16::from(ref_px[2]) - i16::from(act_px[2])).unsigned_abs() as u8;
*dst = Rgba([dr, dg, db, 255]);
}
Ok(out)
}
pub fn evaluate_metrics(
metrics: &DiffMetrics,
max_mean_abs: f32,
max_changed_ratio: f32,
) -> Vec<String> {
let mut violations = Vec::new();
if metrics.mean_abs > max_mean_abs {
violations.push(format!(
"mean_abs {:.4} > allowed {:.4}",
metrics.mean_abs, max_mean_abs
));
}
if metrics.changed_ratio > max_changed_ratio {
violations.push(format!(
"changed_ratio {:.4}% > allowed {:.4}%",
metrics.changed_ratio * 100.0,
max_changed_ratio * 100.0
));
}
violations
}
#[cfg(test)]
mod tests {
use super::*;
fn solid(w: u32, h: u32, r: u8, g: u8, b: u8) -> RgbaImage {
let mut img = RgbaImage::new(w, h);
for px in img.pixels_mut() {
*px = Rgba([r, g, b, 255]);
}
img
}
#[test]
fn compare_identical_images() {
let ref_img = solid(4, 3, 10, 20, 30);
let act_img = solid(4, 3, 10, 20, 30);
let metrics = compare_images(&ref_img, &act_img, 2).expect("comparison must succeed");
assert_eq!(metrics.width, 4);
assert_eq!(metrics.height, 3);
assert_eq!(metrics.max_abs, 0);
assert_eq!(metrics.changed_pixels, 0);
assert_eq!(metrics.mean_abs, 0.0);
assert_eq!(metrics.changed_ratio, 0.0);
}
#[test]
fn compare_detects_changes_and_thresholds() {
let mut ref_img = solid(2, 2, 100, 100, 100);
let mut act_img = solid(2, 2, 100, 100, 100);
ref_img.put_pixel(1, 1, Rgba([120, 100, 100, 255]));
act_img.put_pixel(1, 1, Rgba([100, 100, 100, 255]));
let metrics = compare_images(&ref_img, &act_img, 5).expect("comparison must succeed");
assert_eq!(metrics.max_abs, 20);
assert_eq!(metrics.changed_pixels, 1);
assert!((metrics.changed_ratio - 0.25).abs() < 1e-6);
assert!(metrics.mean_abs > 0.0);
let violations = evaluate_metrics(&metrics, 2.0, 0.20);
assert_eq!(violations.len(), 1);
assert!(violations[0].contains("changed_ratio"));
}
#[test]
fn build_diff_image_returns_per_channel_abs_diff() {
let mut ref_img = solid(1, 1, 100, 150, 200);
let mut act_img = solid(1, 1, 90, 180, 170);
ref_img.put_pixel(0, 0, Rgba([100, 150, 200, 255]));
act_img.put_pixel(0, 0, Rgba([90, 180, 170, 255]));
let diff = build_diff_image(&ref_img, &act_img).expect("diff image must build");
let px = diff.get_pixel(0, 0);
assert_eq!(px[0], 10);
assert_eq!(px[1], 30);
assert_eq!(px[2], 30);
assert_eq!(px[3], 255);
}
}
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