#907: apply Median radius in source pixels without a 4px cap

Radius was clamped to 4 working pixels, so values above 4 matched radius 4
at full resolution. Scale by px_scale and cap only to the image size.

crates/render/src/effects.rs

@@ -101,9 +101,15 @@ pub fn apply(img: &mut Image, e: &EffectInstance, cx: &FxCtx) {
     match e.effect.as_str() {
         "lumetri" => lumetri(img, e, cx),
         "median" => {
-            let r = (f(e, "radius", cx) * cx.px_scale).round().clamp(0.0, 4.0) as isize;
-            if r > 0 {
-                median(img, r);
+            // Radius is authored in source pixels; `px_scale` converts to the working image.
+            // Do not cap at 4 working pixels: that made Radius > 4 look identical at full res.
+            let r = f(e, "radius", cx) * cx.px_scale;
+            if r.is_finite() && r > 0.0 {
+                let cap = img.w.max(img.h).max(1) as f32;
+                let r = r.round().clamp(0.0, cap) as isize;
+                if r > 0 {
+                    median(img, r);
+                }
             }
         }
         "noise" => {

crates/render/tests/median_radius.rs

@@ -0,0 +1,55 @@
+//! Median Radius above 4 must not render as radius 4 at full resolution (`px_scale` 1).
+//!
+//! An 8-pixel-wide green stripe on black: window 9 (r=4) keeps the centre green; window 17 (r=8)
+//! is majority black, so the stripe disappears. A 4-pixel cap would leave both centres green.
+
+use filmcraft_project::{ParamValue, find_effect};
+use filmcraft_render::effects::{FxCtx, apply};
+use filmcraft_render::image::Image;
+use filmcraft_time::Tick;
+
+fn cx() -> FxCtx<'static> {
+    FxCtx {
+        t: Tick::ZERO,
+        px_scale: 1.0,
+        seconds: 0.0,
+        timecode: "00:00:01:00",
+        clip_name: "x",
+        project: None,
+        env: None,
+        working: filmcraft_color::WorkingSpace::Rec709,
+    }
+}
+
+fn green_stripe() -> Image {
+    let (w, h) = (33usize, 17usize);
+    let mut img = Image::filled(w, h, [0.0, 0.0, 0.0, 1.0]);
+    // 8-pixel-wide vertical stripe, centred.
+    for y in 0..h {
+        for x in 12..20 {
+            let i = (y * w + x) * 4;
+            img.px[i..i + 4].copy_from_slice(&[0.0, 1.0, 0.0, 1.0]);
+        }
+    }
+    img
+}
+
+fn apply_radius(radius: f64) -> Image {
+    let mut img = green_stripe();
+    let mut e = find_effect("median").expect("median effect").instance();
+    e.params.get_mut("radius").expect("radius").value = ParamValue::Float(radius);
+    apply(&mut img, &e, &cx());
+    img
+}
+
+#[test]
+fn median_radius_8_is_stronger_than_4_at_full_res() {
+    let r4 = apply_radius(4.0);
+    let r8 = apply_radius(8.0);
+    let cx_px = r4.w / 2;
+    let cy = r4.h / 2;
+    let g4 = r4.get(cx_px, cy)[1];
+    let g8 = r8.get(cx_px, cy)[1];
+    assert!(g4 > 0.9, "radius 4 should keep the 8px stripe (got g={g4})");
+    assert!(g8 < 0.1, "radius 8 should erase the 8px stripe (got g={g8}); a 4px cap would leave it green");
+}