From 720ce5ed7315d48d8d73146b3cecf5448bfa47f9 Mon Sep 17 00:00:00 2001
From: dotCooCoo <RobertLeeLW@gmail.com>
Date: Thu, 15 Oct 2026 04:00:46 -0700
Subject: [PATCH] Effects: Drop Shadow has Darkness, the object's own colors
 with black added
MIME-Version: 1.0
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Content-Transfer-Encoding: 8bit

The reference app's Drop Shadow has a Color and a Darkness, the
percentage of black added to the object's own colors. Drop Shadow had
only a Color, so every shadow was one color. Choosing one or the other,
and the defaults, are VectorCraft's own.

Drop Shadow now takes `shade` ("color" or "darkness", default "color")
and `darkness` (%, default 100). Its dialog and the Appearance panel's
inline editor show Color and Darkness as radio buttons. With Darkness
d, a CMYK document keeps the object's cyan, magenta and yellow and
raises its black from K to K + d × (1 − K), and an RGB document
multiplies each channel by 1 − d, so in RGB 0% gives the object's
color and 100% gives black. A shadow saved without these keys draws as
before. SVG export writes a Darkness shadow with feComponentTransfer
and SVG import reads it back; CSS export leaves it out.

Docs: docs/target-app-parity.md.
---
 crates/effects/src/lib.rs               |   4 +-
 crates/effects/src/raster.rs            |   6 +
 crates/effects/src/tests.rs             |  17 ++-
 crates/eps/src/import/ai/style.rs       |   2 +-
 crates/render/src/fx.rs                 | 183 +++++++++++++++++++++---
 crates/svg/src/css.rs                   |   4 +-
 crates/svg/src/export.rs                |  12 +-
 crates/svg/src/import/fx.rs             |  81 +++++++++--
 crates/svg/tests/css_rules.rs           |  10 ++
 crates/svg/tests/import_live.rs         |  58 +++++++-
 crates/ui-egui/src/dialogs/effect.rs    |  55 ++++++-
 crates/ui-egui/src/dialogs/mod.rs       |   2 +-
 crates/ui-egui/src/dialogs/tests.rs     |  45 ++++++
 crates/ui-egui/src/i18n/cs.tsv          |   1 +
 crates/ui-egui/src/i18n/de.tsv          |   1 +
 crates/ui-egui/src/i18n/es.tsv          |   1 +
 crates/ui-egui/src/i18n/fr.tsv          |   1 +
 crates/ui-egui/src/i18n/hu.tsv          |   1 +
 crates/ui-egui/src/i18n/it.tsv          |   1 +
 crates/ui-egui/src/i18n/ja.tsv          |   1 +
 crates/ui-egui/src/i18n/ko.tsv          |   1 +
 crates/ui-egui/src/i18n/pl.tsv          |   1 +
 crates/ui-egui/src/i18n/ru.tsv          |   1 +
 crates/ui-egui/src/i18n/uk.tsv          |   1 +
 crates/ui-egui/src/i18n/vi.tsv          |   1 +
 crates/ui-egui/src/i18n/zh-hans.tsv     |   1 +
 crates/ui-egui/src/i18n/zh-hant.tsv     |   1 +
 crates/ui-egui/src/panels/appearance.rs |  53 ++++++-
 docs/target-app-parity.md               |   2 +
 29 files changed, 497 insertions(+), 51 deletions(-)

diff --git a/crates/effects/src/lib.rs b/crates/effects/src/lib.rs
index c32558fad..45b8df31a 100644
--- a/crates/effects/src/lib.rs
+++ b/crates/effects/src/lib.rs
@@ -308,8 +308,8 @@ pub fn effect_catalog() -> Vec<EffectInfo> {
             "stylize.dropShadow",
             "Drop Shadow…",
             STYLIZE,
-            "{mode: blend mode (\"multiply\"), opacity: % (75), x: pt (7), y: pt (7), blur: pt (5), color: \"#rrggbb\" (\"#000000\")}",
-            json!({"mode": "multiply", "opacity": 75.0, "x": 7.0, "y": 7.0, "blur": 5.0, "color": "#000000"}),
+            "{mode: blend mode (\"multiply\"), opacity: % (75), x: pt (7), y: pt (7), blur: pt (5), shade: \"color\"|\"darkness\" (\"color\"), color: \"#rrggbb\" (\"#000000\"), darkness: % (100)} (shade \"darkness\": the shadow is the object's own colors with `darkness` percent of black added instead of `color`: in a CMYK document their cyan, magenta and yellow stay and their black K becomes K + darkness × (1 − K); in an RGB document each channel is multiplied by 1 − darkness)",
+            json!({"mode": "multiply", "opacity": 75.0, "x": 7.0, "y": 7.0, "blur": 5.0, "shade": "color", "color": "#000000", "darkness": 100.0}),
         ),
         r(
             "stylize.innerGlow",
diff --git a/crates/effects/src/raster.rs b/crates/effects/src/raster.rs
index 3da990a59..31cc56976 100644
--- a/crates/effects/src/raster.rs
+++ b/crates/effects/src/raster.rs
@@ -21,6 +21,9 @@ pub enum RasterFx {
         dy: f64,
         blur: f64,
         color: Color,
+        /// Darkness (0..1): the shadow is the object's own colors with this share of black added
+        /// instead of `color`; `None` when it is `color`.
+        darkness: Option<f32>,
     },
     OuterGlow {
         mode: BlendMode,
@@ -111,6 +114,9 @@ pub fn raster_effects(effects: &[Effect]) -> Vec<RasterFx> {
                     dy: num(&p, "y", 7.0).clamp(-1e4, 1e4),
                     blur,
                     color: color_param(&p, Color::BLACK),
+                    darkness: text(&p, "shade", "color")
+                        .eq_ignore_ascii_case("darkness")
+                        .then(|| (num(&p, "darkness", 100.0) / 100.0).clamp(0.0, 1.0) as f32),
                 },
                 "stylize.outerGlow" => RasterFx::OuterGlow {
                     mode: blend_mode(text(&p, "mode", "screen")),
diff --git a/crates/effects/src/tests.rs b/crates/effects/src/tests.rs
index 30a8cab2f..bd0517f0e 100644
--- a/crates/effects/src/tests.rs
+++ b/crates/effects/src/tests.rs
@@ -565,11 +565,12 @@ fn raster_effects_parse_and_outset() {
     let r = raster_effects(&list);
     assert_eq!(r.len(), 5);
     match &r[0] {
-        RasterFx::DropShadow { mode, opacity, dx, dy, blur, color } => {
+        RasterFx::DropShadow { mode, opacity, dx, dy, blur, color, darkness } => {
             assert_eq!(*mode, vectorcraft_doc::color::BlendMode::Multiply);
             assert!(close(*opacity as f64, 0.5, 1e-6));
             assert_eq!((*dx, *dy, *blur), (10.0, -4.0, 6.0));
             assert_eq!(color.to_rgb(), [1.0, 0.0, 0.0]);
+            assert_eq!(*darkness, None);
         }
         other => panic!("{other:?}"),
     }
@@ -578,6 +579,20 @@ fn raster_effects_parse_and_outset() {
     assert_eq!(outset(&[], vectorcraft_geom::Rect::ZERO), 0.0);
 }
 
+#[test]
+fn drop_shadow_darkness_replaces_its_color_when_chosen() {
+    let darkness = |params: Value| match raster_effects(&[fx("stylize.dropShadow", params)]).as_slice() {
+        [RasterFx::DropShadow { darkness, .. }] => *darkness,
+        other => panic!("{other:?}"),
+    };
+    assert_eq!(darkness(json!({"shade": "darkness", "darkness": 60})), Some(0.6));
+    assert_eq!(darkness(json!({"shade": "darkness"})), Some(1.0));
+    assert_eq!(darkness(json!({"shade": "darkness", "darkness": 250})), Some(1.0));
+    // Color is the default: a Darkness value alone leaves the shadow its color.
+    assert_eq!(darkness(json!({"darkness": 60})), None);
+    assert_eq!(darkness(json!({})), None);
+}
+
 #[test]
 fn blend_mode_names() {
     use vectorcraft_doc::color::BlendMode;
diff --git a/crates/eps/src/import/ai/style.rs b/crates/eps/src/import/ai/style.rs
index aab101475..37e02fc7e 100644
--- a/crates/eps/src/import/ai/style.rs
+++ b/crates/eps/src/import/ai/style.rs
@@ -344,7 +344,7 @@ fn style(filters: &[Filter]) -> ArtStyle {
                 }),
                 visible: true,
             }),
-            // A shadow darkening the object's own colours isn't one effects describe.
+            // A shadow darkening the object's own colors is not read as Drop Shadow's Darkness.
             SHADOW => plain = false,
             _ => {}
         }
diff --git a/crates/render/src/fx.rs b/crates/render/src/fx.rs
index 4299b77a3..cf5df89e8 100644
--- a/crates/render/src/fx.rs
+++ b/crates/render/src/fx.rs
@@ -308,6 +308,27 @@ fn shadow_filter(dx: f64, dy: f64, blur: f64, color: peniko::Color) -> Filter {
     })
 }
 
+/// The layer filter of a drop shadow with Darkness: the object's own pixels blurred.
+fn shade_filter(blur: f64) -> Filter {
+    Filter::from_primitive(FilterPrimitive::GaussianBlur { std_deviation: (blur / 2.0).max(0.0) as f32, edge_mode: EdgeMode::None })
+}
+
+/// How much darker (0..1) a drop shadow with Darkness `darkness` makes the values `ink` paints:
+/// black added leaves the cyan, magenta and yellow plane of a CMYK document as it is and scales
+/// the complemented black plane, as it scales screen colors, by 1 − `darkness`.
+fn shade(ink: Ink, darkness: f32) -> f32 {
+    match ink {
+        Ink::Cmy => 0.0,
+        Ink::K | Ink::Display | Ink::RichBlack => darkness,
+    }
+}
+
+/// What a shadow or glow raster is made from ([`Made::pixels`]): the silhouette's alpha, or its
+/// premultiplied RGBA when the shadow takes the object's own colors (Darkness).
+fn silhouette(pm: &vello_cpu::Pixmap, colored: bool) -> Vec<u8> {
+    if colored { pm.data().iter().flat_map(|p| [p.r, p.g, p.b, p.a]).collect() } else { pm.data().iter().map(|p| p.a).collect() }
+}
+
 fn pcolor(ink: Ink, c: &vectorcraft_doc::color::Color) -> peniko::Color {
     let [r, g, b] = ink.rgb(c);
     peniko::Color::new([r, g, b, 1.0])
@@ -434,7 +455,7 @@ impl ShadowEntry {
 /// was made draws from that raster ([`Renderer::move_shadow`], [`Renderer::move_pixel_content`]).
 pub(crate) struct Made {
     /// The content's pixels as drawn into the raster before the effects ran: premultiplied RGBA,
-    /// or their alpha alone under a shadow or glow.
+    /// or their alpha alone under a shadow or glow that is one color ([`silhouette`]).
     pixels: Vec<u8>,
     /// The effects run on them.
     fx: Vec<RasterFx>,
@@ -684,9 +705,9 @@ impl Renderer {
         owner: Option<&Arc<Node>>,
         paint: &mut dyn FnMut(&mut Self, &mut RenderContext, &Frame),
     ) -> bool {
-        let (mode, opacity, dx, dy, blur, color) = match fx {
-            RasterFx::DropShadow { mode, opacity, dx, dy, blur, color } => (*mode, *opacity, *dx, *dy, *blur, *color),
-            RasterFx::OuterGlow { mode, opacity, blur, color } => (*mode, *opacity, 0.0, 0.0, *blur, *color),
+        let (mode, opacity, dx, dy, blur, color, darkness) = match fx {
+            RasterFx::DropShadow { mode, opacity, dx, dy, blur, color, darkness } => (*mode, *opacity, *dx, *dy, *blur, *color, *darkness),
+            RasterFx::OuterGlow { mode, opacity, blur, color } => (*mode, *opacity, 0.0, 0.0, *blur, *color, None),
             _ => return false,
         };
         let linear = linear_key(f.view);
@@ -718,7 +739,8 @@ impl Renderer {
                     return false;
                 }
                 let (w, h) = (w as u16, h as u16);
-                // Silhouette (the object's painted alpha), offset by the shadow distance.
+                // Silhouette (the object's painted alpha, and its colors under Darkness), offset by
+                // the shadow distance.
                 let mut off = f.offscreen_context(w, h);
                 let crop = Frame { mt: false, view: Affine::translate((-x0, -y0)) * f.view, ..*f };
                 let before = self.stats.moved;
@@ -730,15 +752,36 @@ impl Renderer {
                 off.render(&mut pm, &mut self.resources);
                 // What the raster is made from, for its object once it moves (`move_shadow`).
                 let made =
-                    Made { pixels: pm.data().iter().map(|p| p.a).collect(), fx: vec![fx.clone()], size: reach.size(), channels: None, outline: None };
+                    Made { pixels: silhouette(&pm, darkness.is_some()), fx: vec![fx.clone()], size: reach.size(), channels: None, outline: None };
                 let (wu, hu) = (w as usize, h as usize);
-                let mut a: Vec<f32> = pm.data().iter().map(|p| p.a as f32).collect();
-                effects::pixel::blur_plane(&mut a, wu, hu, blur / 2.0 / f.px);
-                let [cr, cg, cb] = f.ink.rgb(&color);
-                let tint = |v: f32, ch: f32| (v * ch).round().clamp(0.0, 255.0) as u8;
-                for (px, av) in pm.data_mut().iter_mut().zip(&a) {
-                    let al = (av * opacity).clamp(0.0, 255.0);
-                    *px = vello_cpu::color::PremulRgba8 { r: tint(al, cr), g: tint(al, cg), b: tint(al, cb), a: al.round() as u8 };
+                let sigma = blur / 2.0 / f.px;
+                if let Some(darkness) = darkness {
+                    // The object's own colors, blurred, with the black Darkness adds (premultiplied).
+                    let keep = 1.0 - shade(f.ink, darkness);
+                    let mut planes: [Vec<f32>; 4] = [
+                        pm.data().iter().map(|p| p.r as f32).collect(),
+                        pm.data().iter().map(|p| p.g as f32).collect(),
+                        pm.data().iter().map(|p| p.b as f32).collect(),
+                        pm.data().iter().map(|p| p.a as f32).collect(),
+                    ];
+                    for plane in &mut planes {
+                        effects::pixel::blur_plane(plane, wu, hu, sigma);
+                    }
+                    let [r, g, b, a] = &planes;
+                    for (k, px) in pm.data_mut().iter_mut().enumerate() {
+                        let al = (a[k] * opacity).clamp(0.0, 255.0).round();
+                        let value = |plane: &Vec<f32>| (plane[k] * opacity * keep).round().clamp(0.0, al) as u8;
+                        *px = vello_cpu::color::PremulRgba8 { r: value(r), g: value(g), b: value(b), a: al as u8 };
+                    }
+                } else {
+                    let mut a: Vec<f32> = pm.data().iter().map(|p| p.a as f32).collect();
+                    effects::pixel::blur_plane(&mut a, wu, hu, sigma);
+                    let [cr, cg, cb] = f.ink.rgb(&color);
+                    let tint = |v: f32, ch: f32| (v * ch).round().clamp(0.0, 255.0) as u8;
+                    for (px, av) in pm.data_mut().iter_mut().zip(&a) {
+                        let al = (av * opacity).clamp(0.0, 255.0);
+                        *px = vello_cpu::color::PremulRgba8 { r: tint(al, cr), g: tint(al, cg), b: tint(al, cb), a: al.round() as u8 };
+                    }
                 }
                 let image = std::sync::Arc::new(pm);
                 let anchor = reach.origin();
@@ -768,8 +811,9 @@ impl Renderer {
     /// frame made for its object (the same id, effect slot and ink, at this zoom and rotation, with
     /// the same `inputs`) when only the silhouette's place changed after that frame: made by the
     /// same effect `fx` from a silhouette whose bounds have the size of `reach` (the content's
-    /// bounds moved by the shadow's offset), and whose alpha is the alpha of `n`'s silhouette drawn
-    /// into a raster placed as that one was against its anchor. The raster is kept as `n`'s, marked
+    /// bounds moved by the shadow's offset), and whose alpha (and colors, under Darkness) are those
+    /// of `n`'s silhouette drawn into a raster placed as that one was against its anchor
+    /// ([`silhouette`]). The raster is kept as `n`'s, marked
     /// moved, and is drawn at the nearest whole pixel.
     #[allow(clippy::too_many_arguments)]
     fn move_shadow(
@@ -783,9 +827,9 @@ impl Renderer {
         inputs: &Inputs,
         paint: &mut dyn FnMut(&mut Self, &mut RenderContext, &Frame),
     ) {
-        let (dx, dy) = match fx {
-            RasterFx::DropShadow { dx, dy, .. } => (*dx, *dy),
-            _ => (0.0, 0.0),
+        let (dx, dy, colored) = match fx {
+            RasterFx::DropShadow { dx, dy, darkness, .. } => (*dx, *dy, darkness.is_some()),
+            _ => (0.0, 0.0, false),
         };
         let (linear, stamp, size) = (linear_key(f.view), self.stamp, reach.size());
         let fits = |k: &(usize, usize, Ink), e: &ShadowEntry| {
@@ -809,7 +853,7 @@ impl Renderer {
         off.flush();
         let mut pm = vello_cpu::Pixmap::new(w, h);
         off.render(&mut pm, &mut self.resources);
-        if !self.shadows.get(&old).is_some_and(|e| pm.data().iter().map(|p| p.a).eq(e.made.pixels.iter().copied())) {
+        if !self.shadows.get(&old).is_some_and(|e| silhouette(&pm, colored) == e.made.pixels) {
             return;
         }
         if let Some(mut e) = self.shadows.remove(&old) {
@@ -1028,12 +1072,15 @@ impl Renderer {
             {
                 continue;
             }
-            let (mode, opacity, dx, dy, blur, color) = match fx {
-                RasterFx::DropShadow { mode, opacity, dx, dy, blur, color } => (*mode, *opacity, *dx, *dy, *blur, *color),
-                RasterFx::OuterGlow { mode, opacity, blur, color } => (*mode, *opacity, 0.0, 0.0, *blur, *color),
+            let (mode, opacity, dx, dy, blur, color, darkness) = match fx {
+                RasterFx::DropShadow { mode, opacity, dx, dy, blur, color, darkness } => (*mode, *opacity, *dx, *dy, *blur, *color, *darkness),
+                RasterFx::OuterGlow { mode, opacity, blur, color } => (*mode, *opacity, 0.0, 0.0, *blur, *color, None),
                 _ => continue,
             };
-            let filter = shadow_filter(0.0, 0.0, blur, pcolor(f.ink, &color));
+            let filter = match darkness {
+                Some(_) => shade_filter(blur),
+                None => shadow_filter(0.0, 0.0, blur, pcolor(f.ink, &color)),
+            };
             // The offset moves the content rather than the filter: vello_cpu drops layer content
             // that lies entirely outside the viewport before filtering.
             let reach = reach + Vec2::new(dx, dy);
@@ -1041,6 +1088,14 @@ impl Renderer {
                 c.set_transform(fr.view);
                 c.push_layer(None, comp.map(|m| blend_mode(m.0)), comp.map(|m| m.1), None, Some(filter));
                 paint(r, c, &shifted(fr, dx, dy));
+                // Darkness: black over the object's own colors, keeping their alpha.
+                if let Some(black) = darkness.map(|d| shade(f.ink, d)).filter(|d| *d > 0.0) {
+                    c.set_transform(fr.view);
+                    c.set_blend_mode(peniko::BlendMode::new(peniko::Mix::Normal, peniko::Compose::SrcAtop));
+                    c.set_paint(peniko::Color::new([0.0, 0.0, 0.0, black]));
+                    c.fill_rect(&reach);
+                    c.set_blend_mode(blend_mode(vectorcraft_doc::color::BlendMode::Normal));
+                }
                 c.pop_layer();
             });
         }
@@ -1702,6 +1757,80 @@ mod tests {
         assert_eq!(lum(img.pixel(15, 15)), WHITE);
     }
 
+    /// A red square's drop shadow at Darkness `darkness` (%), opaque and sharp, 10 pt down and
+    /// right; `shade` "color" or "darkness".
+    fn shaded_doc(mode: vectorcraft_doc::ColorMode, fill: Color, shade: &str, darkness: f64) -> Document {
+        let mut d = doc_with(
+            Rect::new(20.0, 20.0, 60.0, 60.0),
+            fill,
+            vec![(
+                "stylize.dropShadow",
+                json!({"x": 10, "y": 10, "blur": 0, "opacity": 100, "mode": "normal", "shade": shade, "darkness": darkness}),
+            )],
+        );
+        d.color_mode = mode;
+        d
+    }
+
+    /// Darkness: the shadow is the object's own color, each channel times 1 − darkness in an RGB
+    /// document (the reference app's guide gives the object's color at 0%,
+    /// <https://help.adobe.com/archive/en/illustrator/cc/2014/illustrator_reference.pdf> page 428), in the cached
+    /// raster and, at 6000 %, in the filter layer that a raster too large to cache is drawn with.
+    #[test]
+    fn drop_shadow_darkness_darkens_the_objects_own_color() {
+        let rgb = vectorcraft_doc::ColorMode::Rgb;
+        let red = Color::rgb(1.0, 0.0, 0.0);
+        // At 6000 %, the view's center is (65, 65), where only the shadow lies.
+        let zoomed = Affine::translate((50.0, 50.0)) * Affine::scale(60.0) * Affine::translate((-65.0, -65.0));
+        for (darkness, want) in [(0.0, 255), (50.0, 128), (100.0, 0)] {
+            let d = shaded_doc(rgb, red, "darkness", darkness);
+            let px = render(&d).pixel(66, 66);
+            assert!(px[0].abs_diff(want) <= 1 && px[1] == 0 && px[2] == 0, "{darkness}%: {px:?}");
+            let opts = RenderOptions { background: Some([255, 255, 255, 255]), ..Default::default() };
+            let px = Renderer::new().render(&d, 100, 100, zoomed, &opts).pixel(50, 50);
+            assert!(px[0].abs_diff(want) <= 1 && px[1] == 0 && px[2] == 0, "{darkness}% at 6000 %: {px:?}");
+        }
+    }
+
+    /// In a CMYK document Darkness adds black ink and keeps the object's cyan, magenta and yellow
+    /// (same page of the guide: at 100% an object with colors other than black gets a shadow of those colors under
+    /// full black, and a black object's shadow is 100% black).
+    #[test]
+    fn drop_shadow_darkness_adds_black_in_a_cmyk_document() {
+        let cmyk = vectorcraft_doc::ColorMode::Cmyk;
+        let inks = |d: &Document| {
+            let i = Renderer::new().render_region_inks(d, Rect::new(0.0, 0.0, 100.0, 100.0), 1.0, &RenderOptions::default());
+            let at = (66 * 100 + 66) * 4;
+            [i[at], i[at + 1], i[at + 2], i[at + 3]]
+        };
+        let red = Color::cmyk(0.0, 1.0, 1.0, 0.0);
+        for (darkness, k) in [(0.0, 0), (50.0, 128), (100.0, 255)] {
+            let got = inks(&shaded_doc(cmyk, red, "darkness", darkness));
+            assert!(got[0] == 0 && got[1] == 255 && got[2] == 255 && got[3].abs_diff(k) <= 1, "{darkness}%: {got:?}");
+        }
+        // Half black ink, darkened by half: K 50 + 50 × 50% = K 75.
+        let got = inks(&shaded_doc(cmyk, Color::cmyk(0.0, 0.0, 0.0, 0.5), "darkness", 50.0));
+        assert!(got[..3] == [0, 0, 0] && got[3].abs_diff(191) <= 1, "{got:?}");
+        let got = inks(&shaded_doc(cmyk, Color::cmyk(0.0, 0.0, 0.0, 1.0), "darkness", 100.0));
+        assert_eq!(got, [0, 0, 0, 255]);
+    }
+
+    /// Color stays the default: a shadow without the new keys, and one with Color chosen and a
+    /// Darkness value, draw the same pixels, which a shadow with Darkness does not.
+    #[test]
+    fn a_drop_shadow_with_color_draws_as_before() {
+        let rgb = vectorcraft_doc::ColorMode::Rgb;
+        let red = Color::rgb(1.0, 0.0, 0.0);
+        let old = doc_with(
+            Rect::new(20.0, 20.0, 60.0, 60.0),
+            red,
+            vec![("stylize.dropShadow", json!({"x": 10, "y": 10, "blur": 0, "opacity": 100, "mode": "normal"}))],
+        );
+        let before = render(&old).pixels;
+        assert_eq!(render(&shaded_doc(rgb, red, "color", 40.0)).pixels, before);
+        assert_ne!(render(&shaded_doc(rgb, red, "darkness", 40.0)).pixels, before);
+    }
+
     #[test]
     fn shadow_of_offscreen_object_is_not_culled() {
         let d = doc_with(
@@ -2009,6 +2138,14 @@ mod tests {
             doc_with(Rect::new(20.0, 20.0, 50.0, 46.0), Color::rgb(0.9, 0.4, 0.1), vec![("stylize.dropShadow", json!({"x": 4, "y": 3, "blur": 2}))]);
         assert_eq!(drag(&shadowed, &moved(&shadowed, false, &recolor)), (1, true), "a shadow under a new color");
         assert_eq!(drag(&shadowed, &moved(&shadowed, false, &notch)), (0, true), "a shadow under a notch");
+        // A shadow with Darkness is made from the object's colors: recolored, it is made again.
+        let shaded = doc_with(
+            Rect::new(20.0, 20.0, 50.0, 46.0),
+            Color::rgb(0.9, 0.4, 0.1),
+            vec![("stylize.dropShadow", json!({"x": 4, "y": 3, "blur": 2, "shade": "darkness", "darkness": 50}))],
+        );
+        assert_eq!(drag(&shaded, &moved(&shaded, false, &|_| {})), (1, true), "a shadow with Darkness, moved");
+        assert_eq!(drag(&shaded, &moved(&shaded, false, &recolor)), (0, true), "a shadow with Darkness under a new color");
     }
 
     /// A raster made over moved rasters counts as moved itself (#1257): a group with a drop shadow
diff --git a/crates/svg/src/css.rs b/crates/svg/src/css.rs
index 58dc65088..aef875a40 100644
--- a/crates/svg/src/css.rs
+++ b/crates/svg/src/css.rs
@@ -570,7 +570,8 @@ impl Rules<'_> {
         }
     }
 
-    /// Shadows and glows as `box-shadow` (type: `text-shadow`), a Gaussian blur as `filter`.
+    /// Shadows and glows as `box-shadow` (type: `text-shadow`), a Gaussian blur as `filter`. A drop
+    /// shadow with Darkness is left out and the art marked unsupported.
     fn effects(&mut self, n: &Node, text: bool, art: &mut Art) {
         let fx = &n.appearance.effects;
         if fx.iter().any(|e| e.visible && !vectorcraft_effects::is_raster(&e.id)) {
@@ -580,6 +581,7 @@ impl Rules<'_> {
         let mut filter = None;
         for f in vectorcraft_effects::raster_effects(fx) {
             match f {
+                RasterFx::DropShadow { darkness: Some(_), .. } => art.unsupported("drop shadows with Darkness"),
                 RasterFx::DropShadow { opacity, dx, dy, blur, color, .. } => {
                     shadows.push(format!("{} {} {} {}", self.len(dx), self.len(dy), self.len(blur), color_css(&color, opacity)))
                 }
diff --git a/crates/svg/src/export.rs b/crates/svg/src/export.rs
index 41632cd0c..b609c1ed2 100644
--- a/crates/svg/src/export.rs
+++ b/crates/svg/src/export.rs
@@ -1581,7 +1581,8 @@ impl Writer<'_> {
     }
 
     /// Raster effects (drop shadow, glows, Gaussian blur, feather) as SVG filters: one `<g filter>`
-    /// per effect, the first effect innermost (the reference app's stacking order). Photoshop-style
+    /// per effect, the first effect innermost (the reference app's stacking order). A drop shadow
+    /// with Darkness darkens the screen colors, in a CMYK document too. Photoshop-style
     /// filters have no SVG equivalent: they are left out with a warning (exports from the app turn
     /// such objects into images first).
     fn filtered(&mut self, n: &Node) {
@@ -1628,6 +1629,15 @@ impl Writer<'_> {
                 format!("<feFlood flood-color=\"{}\" flood-opacity=\"{}\"/>", c.to_hex(), fmt_num(o as f64, 3))
             };
             let body = match f {
+                // Darkness: the object blurred and moved, each color channel times 1 − darkness.
+                RasterFx::DropShadow { opacity, dx, dy, blur, darkness: Some(darkness), .. } => format!(
+                    "<feGaussianBlur in=\"SourceGraphic\" stdDeviation=\"{}\"/><feOffset dx=\"{}\" dy=\"{}\"/><feComponentTransfer result=\"paint\"><feFuncR type=\"linear\" slope=\"{keep}\"/><feFuncG type=\"linear\" slope=\"{keep}\"/><feFuncB type=\"linear\" slope=\"{keep}\"/><feFuncA type=\"linear\" slope=\"{}\"/></feComponentTransfer><feMerge><feMergeNode in=\"paint\"/><feMergeNode in=\"SourceGraphic\"/></feMerge>",
+                    sd(*blur),
+                    self.num(*dx),
+                    self.num(*dy),
+                    fmt_num(*opacity as f64, 3),
+                    keep = fmt_num(1.0 - *darkness as f64, 3)
+                ),
                 RasterFx::DropShadow { opacity, dx, dy, blur, color, .. } => format!(
                     "<feGaussianBlur in=\"SourceAlpha\" stdDeviation=\"{}\"/><feOffset dx=\"{}\" dy=\"{}\" result=\"shadow\"/>{}<feComposite in2=\"shadow\" operator=\"in\" result=\"paint\"/><feMerge><feMergeNode in=\"paint\"/><feMergeNode in=\"SourceGraphic\"/></feMerge>",
                     sd(*blur),
diff --git a/crates/svg/src/import/fx.rs b/crates/svg/src/import/fx.rs
index 9e2d55a20..25f595a30 100644
--- a/crates/svg/src/import/fx.rs
+++ b/crates/svg/src/import/fx.rs
@@ -2,14 +2,15 @@
 //! source, its silhouette blurred, moved or inverted, a colour flood, a coloured silhouette…),
 //! and the result recognised as one of the effects the canvas draws: Gaussian Blur, Drop Shadow,
 //! Outer Glow, Inner Glow or Feather. That covers `feGaussianBlur`, `feDropShadow`, the usual
-//! shadow chains (offset, blur, flood or colour matrix, composite, merge) and what our export
-//! writes, so export → import keeps the effects.
+//! shadow chains (offset, blur, flood or color matrix, composite, merge), the object moved and
+//! blurred with its colors scaled by `feComponentTransfer` (a drop shadow with Darkness) and what
+//! our export writes, so export → import keeps the effects.
 
 use std::collections::HashMap;
 use std::sync::Arc;
 
 use serde_json::json;
-use usvg::filter::{ColorMatrixKind, CompositeOperator, Filter, Input, Kind, TransferFunction};
+use usvg::filter::{ColorInterpolation, ColorMatrixKind, CompositeOperator, Filter, Input, Kind, TransferFunction};
 use usvg::roxmltree;
 use vectorcraft_color::Color;
 use vectorcraft_doc::Effect;
@@ -52,8 +53,8 @@ impl Shape {
 enum V {
     /// `SourceGraphic`.
     Graphic,
-    /// The source blurred (σ).
-    Blurred(f64),
+    /// The source blurred (σ), on linear RGB values when `true`.
+    Blurred(f64, bool),
     /// A black silhouette.
     Alpha(Shape),
     Flood(Color, f32),
@@ -66,6 +67,16 @@ enum V {
     },
     /// The source inside its own blurred silhouette (σ).
     Feathered(f64),
+    /// The source blurred (σ `sd`, on linear RGB values when `linear`), moved, its colors times
+    /// `keep` and its alpha times `opacity`: a drop shadow with Darkness 1 − `keep`.
+    Shade {
+        sd: f64,
+        linear: bool,
+        dx: f64,
+        dy: f64,
+        keep: f32,
+        opacity: f32,
+    },
     /// Layers, bottom first.
     Stack(Vec<V>),
 }
@@ -78,17 +89,18 @@ impl V {
         }
     }
 
-    /// Blurred by σ `sd` (blurs add up as variances).
-    fn blur(self, sd: f64) -> Option<V> {
+    /// Blurred by σ `sd` (blurs add up as variances), on linear RGB values when `linear`.
+    fn blur(self, sd: f64, linear: bool) -> Option<V> {
         let add = |a: f64| (a * a + sd * sd).sqrt();
         Some(match self {
             v if sd <= 0.0 => v,
-            V::Graphic => V::Blurred(sd),
-            V::Blurred(a) => V::Blurred(add(a)),
+            V::Graphic => V::Blurred(sd, linear),
+            V::Blurred(a, l) => V::Blurred(add(a), l || linear),
             V::Alpha(s) => V::Alpha(Shape { sd: add(s.sd), ..s }),
             V::Paint { shape, color, opacity, clipped: false } => {
                 V::Paint { shape: Shape { sd: add(shape.sd), ..shape }, color, opacity, clipped: false }
             }
+            V::Shade { sd: s, linear: l, dx, dy, keep, opacity } => V::Shade { sd: add(s), linear: l || linear, dx, dy, keep, opacity },
             _ => return None,
         })
     }
@@ -98,11 +110,26 @@ impl V {
         Some(match self {
             V::Alpha(s) => V::Alpha(moved(s)),
             V::Paint { shape, color, opacity, clipped: false } => V::Paint { shape: moved(shape), color, opacity, clipped: false },
-            v @ (V::Graphic | V::Blurred(_)) if dx == 0.0 && dy == 0.0 => v,
+            v @ (V::Graphic | V::Blurred(..)) if dx == 0.0 && dy == 0.0 => v,
+            V::Graphic => V::Shade { sd: 0.0, linear: false, dx, dy, keep: 1.0, opacity: 1.0 },
+            V::Blurred(sd, linear) => V::Shade { sd, linear, dx, dy, keep: 1.0, opacity: 1.0 },
+            V::Shade { sd, linear, dx: x, dy: y, keep, opacity } => V::Shade { sd, linear, dx: x + dx, dy: y + dy, keep, opacity },
             _ => return None,
         })
     }
 
+    /// The source, blurred or moved, with each color channel times `keep` and its alpha times
+    /// `opacity` (`feComponentTransfer` with linear functions through 0).
+    fn scaled(self, keep: f32, opacity: f32) -> Option<V> {
+        let (sd, linear, dx, dy, k, o) = match self {
+            V::Graphic => (0.0, false, 0.0, 0.0, 1.0, 1.0),
+            V::Blurred(sd, linear) => (sd, linear, 0.0, 0.0, 1.0, 1.0),
+            V::Shade { sd, linear, dx, dy, keep, opacity } => (sd, linear, dx, dy, keep, opacity),
+            _ => return None,
+        };
+        Some(V::Shade { sd, linear, dx, dy, keep: k * keep, opacity: o * opacity })
+    }
+
     /// `self` in the alpha of `mask` (`feComposite operator="in"`).
     fn inside(self, mask: V) -> Option<V> {
         // The source's alpha is its silhouette.
@@ -124,7 +151,7 @@ impl V {
     fn color_matrix(self, m: &[f32]) -> Option<V> {
         let shape = match self {
             V::Alpha(s) => s,
-            V::Blurred(sd) => Shape { sd, ..Shape::default() },
+            V::Blurred(sd, _) => Shape { sd, ..Shape::default() },
             _ => return None,
         };
         let row = |r: usize| m.get(r * 5..r * 5 + 5);
@@ -163,7 +190,10 @@ fn eval(f: &Filter) -> Option<V> {
             }
         };
         let v = match p.kind() {
-            Kind::GaussianBlur(b) => input(b.input())?.blur(sd(b.std_dev_x().get(), b.std_dev_y().get()))?,
+            Kind::GaussianBlur(b) => {
+                let linear = p.color_interpolation() == ColorInterpolation::LinearRGB;
+                input(b.input())?.blur(sd(b.std_dev_x().get(), b.std_dev_y().get()), linear)?
+            }
             Kind::Offset(o) => input(o.input())?.offset(o.dx() as f64, o.dy() as f64)?,
             Kind::Flood(fl) => V::Flood(color(fl.color()), fl.opacity().get()),
             Kind::Composite(c) => {
@@ -186,8 +216,22 @@ fn eval(f: &Filter) -> Option<V> {
                     TransferFunction::Linear { slope, intercept } => *slope == -1.0 && *intercept == 1.0,
                     _ => false,
                 };
-                match input(c.input())? {
-                    V::Alpha(s) if identity && invert && s.sd == 0.0 => V::Alpha(Shape { inverted: !s.inverted, ..s }),
+                // A scale (a linear function through 0, or none) of each channel.
+                let scale = |f: &TransferFunction| match f {
+                    TransferFunction::Identity => Some(1.0),
+                    TransferFunction::Linear { slope, intercept } if *intercept == 0.0 && (0.0..=1.0).contains(slope) => Some(*slope),
+                    _ => None,
+                };
+                // The same scale of R, G and B, on sRGB values (a scale of 0 or 1 is the same on
+                // linear ones).
+                let srgb = p.color_interpolation() == ColorInterpolation::SRGB;
+                let keep = match [c.func_r(), c.func_g(), c.func_b()].map(scale) {
+                    [Some(r), Some(g), Some(b)] if r == g && g == b && (srgb || r == 0.0 || r == 1.0) => Some(r),
+                    _ => None,
+                };
+                match (input(c.input())?, keep, scale(c.func_a())) {
+                    (V::Alpha(s), _, _) if identity && invert && s.sd == 0.0 => V::Alpha(Shape { inverted: !s.inverted, ..s }),
+                    (v @ (V::Graphic | V::Blurred(..) | V::Shade { .. }), Some(keep), Some(opacity)) => v.scaled(keep, opacity)?,
                     _ => return None,
                 }
             }
@@ -219,7 +263,7 @@ pub(super) fn effects(filters: &[Arc<Filter>], ts: Affine, blends: &HashMap<Stri
         let paint = |c: Color, o: f32| (c.to_hex(), num(o as f64 * 100.0));
         let (id, params) = match eval(f)? {
             V::Graphic => continue,
-            V::Blurred(sd) => ("blur.gaussian", json!({ "radius": blur(sd) })),
+            V::Blurred(sd, _) => ("blur.gaussian", json!({ "radius": blur(sd) })),
             V::Feathered(sd) => ("stylize.feather", json!({ "radius": blur(sd) })),
             V::Stack(layers) => match layers.as_slice() {
                 [V::Paint { shape, color, opacity, clipped: false }, V::Graphic] if !shape.inverted => {
@@ -232,6 +276,13 @@ pub(super) fn effects(filters: &[Arc<Filter>], ts: Affine, blends: &HashMap<Stri
                         ("stylize.outerGlow", json!({ "blur": blur(shape.sd), "color": color, "opacity": opacity, "mode": mode }))
                     }
                 }
+                // A drop shadow with Darkness below 100% blurs the object's sRGB values.
+                [V::Shade { sd, linear, dx, dy, keep, opacity }, V::Graphic] if !*linear || *keep == 0.0 => {
+                    let v = along(*dx, *dy);
+                    let (darkness, opacity) = (num((1.0 - *keep as f64) * 100.0), num(*opacity as f64 * 100.0));
+                    let p = json!({ "x": num(v.x), "y": num(v.y), "blur": blur(*sd), "shade": "darkness", "darkness": darkness, "opacity": opacity, "mode": mode });
+                    ("stylize.dropShadow", p)
+                }
                 [V::Graphic, V::Paint { shape, color, opacity, clipped: true }] if !shape.moved => {
                     let (color, opacity) = paint(*color, *opacity);
                     let source = if shape.inverted { "edge" } else { "center" };
diff --git a/crates/svg/tests/css_rules.rs b/crates/svg/tests/css_rules.rs
index e50d29a0b..654a522db 100644
--- a/crates/svg/tests/css_rules.rs
+++ b/crates/svg/tests/css_rules.rs
@@ -220,6 +220,16 @@ fn shadows_and_unsupported_art() {
     let id = add(&mut d, n);
     let r = one(&d, id, &CssOptions::default());
     assert_eq!(prop(&r, "box-shadow"), Some("2px 3px 4px rgba(0, 0, 0, 0.5)"));
+    // A shadow with Darkness takes the object's own colors, which a CSS shadow can't.
+    let mut n = rect(&mut d, (0.0, 0.0, 50.0, 50.0), 0.0);
+    n.appearance.effects.push(Effect {
+        id: "stylize.dropShadow".into(),
+        params: serde_json::json!({"x": 2, "y": 3, "blur": 4, "opacity": 50, "shade": "darkness"}),
+        visible: true,
+    });
+    let shaded = add(&mut d, n);
+    let r = one(&d, shaded, &CssOptions::default());
+    assert!(prop(&r, "box-shadow").is_none() && r.unsupported.is_some(), "{r:?}");
     // A star is no box: described as its box, or with rasterize as its picture.
     let star = Node::path(
         d.alloc_id(),
diff --git a/crates/svg/tests/import_live.rs b/crates/svg/tests/import_live.rs
index 3dcc152bc..8715727cc 100644
--- a/crates/svg/tests/import_live.rs
+++ b/crates/svg/tests/import_live.rs
@@ -184,8 +184,9 @@ fn a_gaussian_blur_becomes_the_effect_with_its_radius() {
 fn shadow(d: &Document) -> (f64, f64, f64, Color, f32) {
     let fx = vectorcraft_effects::raster_effects(&effects(d));
     match fx.as_slice() {
-        [RasterFx::DropShadow { dx, dy, blur, color, opacity, mode }] => {
+        [RasterFx::DropShadow { dx, dy, blur, color, opacity, mode, darkness }] => {
             assert_eq!(*mode, BlendMode::Normal, "filters composite normally");
+            assert_eq!(*darkness, None);
             (*dx, *dy, *blur, *color, (opacity * 100.0).round())
         }
         other => panic!("{other:?}"),
@@ -214,6 +215,38 @@ fn drop_shadow_chains_become_drop_shadows() {
     }
 }
 
+/// The object blurred, moved and its colors scaled under it is a drop shadow with Darkness when
+/// the blur and the scale work on sRGB values, or when the scale is 0; otherwise, on linear RGB
+/// values (the SVG default), it is reported. A blur on linear values whose result goes unused
+/// does not count.
+#[test]
+fn a_darkened_copy_of_the_object_becomes_a_drop_shadow_with_darkness() {
+    let chain = |space: &str, transfer: &str, slope: f64| {
+        format!(
+            r##"<defs><filter id="s"{space}><feGaussianBlur in="SourceGraphic" stdDeviation="3" color-interpolation-filters="linearRGB" result="unused"/><feGaussianBlur in="SourceGraphic" stdDeviation="2"/><feOffset dx="4" dy="5"/><feComponentTransfer result="p"{transfer}><feFuncR type="linear" slope="{slope}"/><feFuncG type="linear" slope="{slope}"/><feFuncB type="linear" slope="{slope}"/><feFuncA type="linear" slope="0.6"/></feComponentTransfer><feMerge><feMergeNode in="p"/><feMergeNode in="SourceGraphic"/></feMerge></filter></defs><rect x="50" y="30" width="60" height="40" fill="#f00" filter="url(#s)"/>"##
+        )
+    };
+    let srgb = r#" color-interpolation-filters="sRGB""#;
+    // The scale 0 makes black whatever values it works on.
+    for (space, slope, darkness) in [(srgb, 0.5, 50.0), ("", 0.0, 100.0)] {
+        let (d, w) = open(&chain(space, "", slope));
+        assert!(w.is_empty(), "{w:?}");
+        let fx = effects(&d);
+        let p = &fx[0].params;
+        assert_eq!(
+            (fx[0].id.as_str(), &p["shade"], &p["darkness"], &p["opacity"]),
+            ("stylize.dropShadow", &json!("darkness"), &json!(darkness), &json!(60.0))
+        );
+        assert_eq!((&p["x"], &p["y"], &p["blur"]), (&json!(4.0), &json!(5.0), &json!(4.0)));
+    }
+    // Scaled on linear values, or blurred on them before an sRGB scale.
+    for (space, transfer) in [("", ""), ("", srgb)] {
+        let (d, w) = open(&chain(space, transfer, 0.5));
+        assert!(w.iter().any(|w| w.contains("filter")), "{transfer}: {w:?}");
+        assert!(effects(&d).is_empty());
+    }
+}
+
 #[test]
 fn other_filters_are_reported() {
     let (d, w) =
@@ -239,6 +272,7 @@ fn exported_effects_import_as_the_same_effects() {
     let fx = |id: &str, p: serde_json::Value| Effect { id: id.into(), params: p, visible: true };
     let cases = [
         vec![fx("stylize.dropShadow", json!({"x": 7.0, "y": -3.0, "blur": 5.0, "opacity": 60.0, "color": "#203040"}))],
+        vec![fx("stylize.dropShadow", json!({"x": 7.0, "y": -3.0, "blur": 5.0, "opacity": 60.0, "shade": "darkness", "darkness": 40.0}))],
         vec![fx("stylize.outerGlow", json!({"blur": 8.0, "color": "#ffcc00", "opacity": 80.0}))],
         vec![fx("stylize.innerGlow", json!({"blur": 6.0, "color": "#ffffff", "source": "edge", "mode": "normal"}))],
         vec![fx("stylize.innerGlow", json!({"blur": 6.0, "color": "#00ff00", "source": "center", "mode": "multiply"}))],
@@ -259,6 +293,28 @@ fn exported_effects_import_as_the_same_effects() {
     }
 }
 
+#[test]
+fn a_drop_shadow_with_darkness_exports_as_the_canvas_draws_it() {
+    let mut d = Document::new(200.0, 120.0);
+    let mut n = Node::path(
+        d.alloc_id(),
+        shapes::rectangle(Rect::new(40.0, 20.0, 100.0, 70.0)),
+        Appearance::basic(Paint::solid(Color::rgb(1.0, 0.0, 0.0)), Paint::None, 0.0),
+    );
+    let shadow = json!({"x": 30.0, "y": 30.0, "blur": 0.0, "opacity": 100.0, "mode": "normal", "shade": "darkness", "darkness": 50.0});
+    n.appearance.effects = vec![Effect { id: "stylize.dropShadow".into(), params: shadow, visible: true }];
+    let l = d.layers[0].id;
+    d.insert(Some(l), 0, n).unwrap();
+    let svg = export(&d, &ExportOptions::default());
+    let (canvas, exported) = (render_artboard(&d), resvg_render(&svg, 200, 120));
+    // Where only the shadow lies: the red at half its value.
+    for img in [&canvas, &exported] {
+        let [r, g, b] = img.over_white(115, 90);
+        assert!(r.abs_diff(128) <= 2 && g <= 2 && b <= 2, "{:?}", [r, g, b]);
+    }
+    assert_similar(&canvas, &exported, 40.0, 0.02);
+}
+
 #[test]
 fn symbols_and_effects_export_import_export_is_stable() {
     // A doc with a symbol instance carrying a shadow: export → import → export is stable.
diff --git a/crates/ui-egui/src/dialogs/effect.rs b/crates/ui-egui/src/dialogs/effect.rs
index da3a84760..e95055f75 100644
--- a/crates/ui-egui/src/dialogs/effect.rs
+++ b/crates/ui-egui/src/dialogs/effect.rs
@@ -139,6 +139,7 @@ fn body(app: &mut VectorcraftApp, ui: &mut egui::Ui, d: &mut Dialog) -> bool {
         None if vectorcraft_effects::is_adjustment(&id) => adjust_fields(ui, d),
         None if id == TRANSFORM => transform_fields(ui, d, app.session.general_unit()),
         None if id == ZIG_ZAG => zig_zag_fields(ui, d, app.session.general_unit()),
+        None if id == DROP_SHADOW => drop_shadow_fields(ui, d, app.session.general_unit()),
         None if id == "artistic.filmGrain" => film_grain_fields(ui, d),
         None => {
             let doc = vectorcraft_effects::effect_info(&id).map(|e| e.params).unwrap_or_default();
@@ -197,6 +198,7 @@ fn choices(effect: &str, key: &str) -> Option<form::Choices> {
         ("video.deinterlace", "eliminate") => Some(&[("Odd Fields", "odd"), ("Even Fields", "even")]),
         ("video.deinterlace", "create") => Some(&[("Duplication", "duplication"), ("Interpolation", "interpolation")]),
         ("stylize.innerGlow", "source") => Some(&[("Center", "center"), ("Edge", "edge")]),
+        ("stylize.dropShadow", "shade") => Some(SHADES),
         ("path.offsetPath", "joins") => Some(&[("Miter", "miter"), ("Round", "round"), ("Bevel", "bevel")]),
         ("distort.roughen" | "distort.zigZag", "points") => Some(&[("Smooth", "smooth"), ("Corner", "corner")]),
         _ => None,
@@ -385,6 +387,49 @@ fn zig_zag_fields(ui: &mut egui::Ui, d: &mut Dialog, unit: vectorcraft_doc::Unit
     values_changed(d)
 }
 
+/// Drop Shadow (Effect › Stylize › Drop Shadow…).
+const DROP_SHADOW: &str = "stylize.dropShadow";
+
+/// What Drop Shadow's shadow takes its color from (`shade`), as (label, value).
+pub(crate) const SHADES: form::Choices = &[("Color", "color"), ("Darkness", "darkness")];
+
+/// Drop Shadow's dialog: Mode, Opacity, the offsets and Blur as the other effects show them, then
+/// Color and Darkness as radio buttons, each with its field (the field of the one not chosen is
+/// dimmed). Returns whether the values differ from those last previewed.
+fn drop_shadow_fields(ui: &mut egui::Ui, d: &mut Dialog, unit: vectorcraft_doc::Unit) -> bool {
+    let doc = vectorcraft_effects::effect_info(DROP_SHADOW).map(|e| e.params).unwrap_or_default();
+    // The generic rows, without the three this dialog shows as radio buttons.
+    let own: Vec<(String, Value)> = ["shade", "color", "darkness"].iter().filter_map(|k| d.fields.remove(*k).map(|v| (k.to_string(), v))).collect();
+    form::param_fields(ui, d, &|k| vectorcraft_effects::is_length(DROP_SHADOW, k, false), &|k| choices(DROP_SHADOW, k), &|k| doc_rank(doc, k), unit);
+    d.fields.extend(own);
+    let darkness = d.str("shade").eq_ignore_ascii_case("darkness");
+    ui.add_space(4.0);
+    egui::Grid::new("fx-shade").num_columns(2).spacing([12.0, 8.0]).show(ui, |ui| {
+        if widgets::radio(ui, tl!("Color"), !darkness, true) {
+            d.fields.insert("shade".into(), json!("color"));
+        }
+        ui.add_enabled_ui(!darkness, |ui| match d.fields.get("color") {
+            Some(Value::String(_)) | None => {
+                form::text(ui, d, "color", 128.0);
+            }
+            Some(other) => {
+                widgets::dim_label(ui, &other.to_string());
+            }
+        });
+        ui.end_row();
+        if widgets::radio(ui, tl!("Darkness"), darkness, true) {
+            d.fields.insert("shade".into(), json!("darkness"));
+        }
+        ui.add_enabled_ui(darkness, |ui| {
+            if let Some(v) = widgets::range_field(ui, "fx-darkness", d.f64("darkness", 100.0), 0.0..=100.0, "%", 0, 70.0) {
+                d.fields.insert("darkness".into(), json!(v));
+            }
+        });
+        ui.end_row();
+    });
+    values_changed(d)
+}
+
 /// Curves' graph of its `points` (input across, output up, 0..255): drag a point to move it
 /// between its neighbours, press on the graph away from the points to add one there, drag one
 /// off the graph to remove it (two always stay).
@@ -499,9 +544,13 @@ mod tests {
     #[test]
     fn fields_that_pick_a_value_are_dropdowns_of_its_values() {
         // The values come from the effect's parameter documentation (`joins: "miter"|"round"|…`).
-        for (effect, key) in
-            [("path.offsetPath", "joins"), ("distort.zigZag", "points"), ("distort.roughen", "points"), ("stylize.innerGlow", "source")]
-        {
+        for (effect, key) in [
+            ("path.offsetPath", "joins"),
+            ("distort.zigZag", "points"),
+            ("distort.roughen", "points"),
+            ("stylize.innerGlow", "source"),
+            (DROP_SHADOW, "shade"),
+        ] {
             let doc = vectorcraft_effects::effect_info(effect).unwrap().params;
             let listed = doc.split(&format!("{key}: ")).nth(1).unwrap().split([',', '}', ' ']).next().unwrap().to_string();
             let values: Vec<String> = choices(effect, key).unwrap().iter().map(|(_, v)| format!("\"{v}\"")).collect();
diff --git a/crates/ui-egui/src/dialogs/mod.rs b/crates/ui-egui/src/dialogs/mod.rs
index c54ec1465..4bb017ae0 100644
--- a/crates/ui-egui/src/dialogs/mod.rs
+++ b/crates/ui-egui/src/dialogs/mod.rs
@@ -103,8 +103,8 @@ use serde_json::{Value, json};
 
 pub use color_picker::open as open_color_picker;
 pub use document_setup::open as open_document_setup;
-pub(crate) use effect::FILM_GRAIN_FIELDS;
 pub use effect::open as open_effect_dialog;
+pub(crate) use effect::{FILM_GRAIN_FIELDS, SHADES};
 pub use export_as::open as open_export_as;
 pub use export_for_screens::open as open_export_for_screens;
 pub(crate) use export_for_screens::{
diff --git a/crates/ui-egui/src/dialogs/tests.rs b/crates/ui-egui/src/dialogs/tests.rs
index e3f6e0726..f60a29d1a 100644
--- a/crates/ui-egui/src/dialogs/tests.rs
+++ b/crates/ui-egui/src/dialogs/tests.rs
@@ -748,6 +748,51 @@ fn the_transform_effect_dialog_has_its_controls_previews_them_and_shows_them_aga
     assert!(text.lines().any(|l| l == "Reference Point"), "{text}");
 }
 
+/// Drop Shadow's dialog has Color and Darkness as radio buttons, each with its field; a click on
+/// Darkness previews the shadow with it and OK applies it.
+#[test]
+fn drop_shadow_chooses_color_or_darkness() {
+    let mut app = app();
+    let id = app.run("shape.rectangle", json!({"x": 10, "y": 10, "width": 50, "height": 50})).unwrap()["id"].as_u64().unwrap();
+    app.run("effect.dialog", json!({"effect": "stylize.dropShadow"})).unwrap();
+    let ctx = egui::Context::default();
+    theme::install_fonts(&ctx);
+    theme::apply(&ctx, Default::default());
+    let mut time = 0.0;
+    let mut run = |app: &mut VectorcraftApp, events: Vec<egui::Event>| {
+        time += 0.1;
+        let mut out = ctx.run_ui(egui::RawInput { events, time: Some(time), ..Default::default() }, |ui| show(app, ui.ctx()));
+        out.textures_delta.clear();
+        out
+    };
+    run(&mut app, vec![]);
+    let out = run(&mut app, vec![]);
+    let text = crate::tests_labels::shapes_text(&out);
+    let lines: Vec<&str> = text.lines().map(str::trim).collect();
+    for want in ["Mode:", "Opacity:", "Blur:", "Color", "Darkness"] {
+        assert!(lines.contains(&want), "no {want:?} in {lines:?}");
+    }
+    assert!(!lines.contains(&"Shade:"), "{lines:?}");
+    fn find(shape: &egui::Shape) -> Option<egui::Pos2> {
+        match shape {
+            egui::Shape::Text(t) if t.galley.text().trim() == "Darkness" => Some(t.visual_bounding_rect().center()),
+            egui::Shape::Vec(v) => v.iter().find_map(find),
+            _ => None,
+        }
+    }
+    let at = out.shapes.iter().find_map(|s| find(&s.shape)).unwrap();
+    let button = |pressed| egui::Event::PointerButton { pos: at, button: egui::PointerButton::Primary, pressed, modifiers: Default::default() };
+    for events in [vec![egui::Event::PointerMoved(at)], vec![button(true)], vec![button(false)], vec![], vec![]] {
+        run(&mut app, events);
+    }
+    let effect = |app: &VectorcraftApp| app.session.doc().unwrap().doc.node(vectorcraft_doc::NodeId(id)).unwrap().appearance.effects[0].clone();
+    assert!(app.session.in_interaction(), "the preview runs");
+    assert_eq!(effect(&app).params["shade"], json!("darkness"));
+    confirm(&mut app).unwrap();
+    let params = effect(&app).params;
+    assert_eq!((params["shade"].clone(), params["darkness"].clone()), (json!("darkness"), json!(100.0)));
+}
+
 #[test]
 fn artboard_options_position_moves_art_only_with_the_tool_option_on() {
     for move_art in [false, true] {
diff --git a/crates/ui-egui/src/i18n/cs.tsv b/crates/ui-egui/src/i18n/cs.tsv
index 9834a73f4..71d0548d0 100644
--- a/crates/ui-egui/src/i18n/cs.tsv
+++ b/crates/ui-egui/src/i18n/cs.tsv
@@ -436,6 +436,7 @@
 	Round Corners…	Zaoblit rohy…
 	Scribble…	Čmáranice…
 	Drop Shadow…	Vržený stín…
+	Darkness	Tmavost
 	Inner Glow…	Vnitřní záře…
 	Outer Glow…	Vnější záře…
 	Feather…	Měkké okraje…
diff --git a/crates/ui-egui/src/i18n/de.tsv b/crates/ui-egui/src/i18n/de.tsv
index 840a5f1cc..68eba1886 100644
--- a/crates/ui-egui/src/i18n/de.tsv
+++ b/crates/ui-egui/src/i18n/de.tsv
@@ -638,6 +638,7 @@
 	Cyan	Cyan
 	Dark	Dunkel
 	Darken	Abdunkeln
+	Darkness	Dunkelheit
 	dash	Strich
 	Dash Pattern	Strichmuster
 	Dashed	Gestrichelt
diff --git a/crates/ui-egui/src/i18n/es.tsv b/crates/ui-egui/src/i18n/es.tsv
index eab75bf95..8a5717927 100644
--- a/crates/ui-egui/src/i18n/es.tsv
+++ b/crates/ui-egui/src/i18n/es.tsv
@@ -652,6 +652,7 @@
 	Cyan	Cian
 	Dark	Oscuro
 	Darken	Oscurecer
+	Darkness	Oscuridad
 	dash	guion
 	Dash Pattern	Patrón de guiones
 	Dashed	Discontinuo
diff --git a/crates/ui-egui/src/i18n/fr.tsv b/crates/ui-egui/src/i18n/fr.tsv
index d0eb66c23..1ef3d9db3 100644
--- a/crates/ui-egui/src/i18n/fr.tsv
+++ b/crates/ui-egui/src/i18n/fr.tsv
@@ -654,6 +654,7 @@
 	Cyan	Cyan
 	Dark	Sombre
 	Darken	Obscurcir
+	Darkness	Obscurité
 	dash	tiret
 	Dash Pattern	Motif de tirets
 	Dashed	Pointillés
diff --git a/crates/ui-egui/src/i18n/hu.tsv b/crates/ui-egui/src/i18n/hu.tsv
index 2e2622acd..5989a4079 100644
--- a/crates/ui-egui/src/i18n/hu.tsv
+++ b/crates/ui-egui/src/i18n/hu.tsv
@@ -867,6 +867,7 @@
 	Dark Strokes	Sötét vonások
 	Dark Strokes…	Sötét vonások…
 	Darken	Sötétítés
+	Darkness	Sötétség
 	dash	vonal
 	Dash Pattern	Szaggatás mintázata
 	Dashed	Szaggatott
diff --git a/crates/ui-egui/src/i18n/it.tsv b/crates/ui-egui/src/i18n/it.tsv
index d32558078..4fc5a29b2 100644
--- a/crates/ui-egui/src/i18n/it.tsv
+++ b/crates/ui-egui/src/i18n/it.tsv
@@ -652,6 +652,7 @@
 	Cyan	Ciano
 	Dark	Scuro
 	Darken	Scurisci
+	Darkness	Oscurità
 	dash	trattino
 	Dash Pattern	Schema del tratteggio
 	Dashed	Tratteggiato
diff --git a/crates/ui-egui/src/i18n/ja.tsv b/crates/ui-egui/src/i18n/ja.tsv
index 60b0feee0..c126dac5b 100644
--- a/crates/ui-egui/src/i18n/ja.tsv
+++ b/crates/ui-egui/src/i18n/ja.tsv
@@ -1135,6 +1135,7 @@
 	DXF Options	DXF オプション
 	DXF Options Dialog	DXF オプションダイアログ
 	Darken	比較 (暗)
+	Darkness	濃さ
 	Dashed	破線
 	Dashed Line	破線
 	Data Recovery	データ復帰
diff --git a/crates/ui-egui/src/i18n/ko.tsv b/crates/ui-egui/src/i18n/ko.tsv
index 35e877f4d..ff0a0b02f 100644
--- a/crates/ui-egui/src/i18n/ko.tsv
+++ b/crates/ui-egui/src/i18n/ko.tsv
@@ -1130,6 +1130,7 @@
 	DXF Options	DXF 옵션
 	DXF Options Dialog	DXF 옵션 대화상자
 	Darken	어둡게
+	Darkness	어둡기
 	Dashed	점선
 	Dashed Line	점선
 	Data Recovery	데이터 복구
diff --git a/crates/ui-egui/src/i18n/pl.tsv b/crates/ui-egui/src/i18n/pl.tsv
index aa8178fe4..9af5c261d 100644
--- a/crates/ui-egui/src/i18n/pl.tsv
+++ b/crates/ui-egui/src/i18n/pl.tsv
@@ -396,6 +396,7 @@
 	Round Corners…	Zaokrąglij narożniki…
 	Scribble…	Bazgroły…
 	Drop Shadow…	Cień…
+	Darkness	Zaciemnienie
 	Inner Glow…	Blask wewnętrzny…
 	Outer Glow…	Blask zewnętrzny…
 	Feather…	Wtapianie…
diff --git a/crates/ui-egui/src/i18n/ru.tsv b/crates/ui-egui/src/i18n/ru.tsv
index c793256e8..f03b1efdf 100644
--- a/crates/ui-egui/src/i18n/ru.tsv
+++ b/crates/ui-egui/src/i18n/ru.tsv
@@ -650,6 +650,7 @@
 	Cyan	Голубой
 	Dark	Тёмный
 	Darken	Замена тёмным
+	Darkness	Затемнение
 	dash	штрих
 	Dash Pattern	Шаблон штрихов
 	Dashed	Штриховой
diff --git a/crates/ui-egui/src/i18n/uk.tsv b/crates/ui-egui/src/i18n/uk.tsv
index a2c4a40ca..87fbe7b57 100644
--- a/crates/ui-egui/src/i18n/uk.tsv
+++ b/crates/ui-egui/src/i18n/uk.tsv
@@ -646,6 +646,7 @@
 	Cyan	Блакитний
 	Dark	Темний
 	Darken	Затемнення
+	Darkness	Темність
 	dash	штрих
 	Dash Pattern	Шаблон штрихів
 	Dashed	Штриховий
diff --git a/crates/ui-egui/src/i18n/vi.tsv b/crates/ui-egui/src/i18n/vi.tsv
index a66ca0641..ad468749a 100644
--- a/crates/ui-egui/src/i18n/vi.tsv
+++ b/crates/ui-egui/src/i18n/vi.tsv
@@ -764,6 +764,7 @@
 	Dark Strokes	Nét tối
 	Dark Strokes…	Nét tối…
 	Darken	Làm tối
+	Darkness	Độ tối
 	dash	nét đứt
 	Dash Pattern	Mẫu nét đứt
 	Dashed	Nét đứt
diff --git a/crates/ui-egui/src/i18n/zh-hans.tsv b/crates/ui-egui/src/i18n/zh-hans.tsv
index a845dfc8d..3dd105ef2 100644
--- a/crates/ui-egui/src/i18n/zh-hans.tsv
+++ b/crates/ui-egui/src/i18n/zh-hans.tsv
@@ -610,6 +610,7 @@
 	Cyan	青
 	Dark	深色
 	Darken	变暗
+	Darkness	暗度
 	dash	虚线
 	Dash Pattern	虚线样式
 	Dashed	虚线
diff --git a/crates/ui-egui/src/i18n/zh-hant.tsv b/crates/ui-egui/src/i18n/zh-hant.tsv
index 20f589c21..920b54bae 100644
--- a/crates/ui-egui/src/i18n/zh-hant.tsv
+++ b/crates/ui-egui/src/i18n/zh-hant.tsv
@@ -625,6 +625,7 @@
 	Cyan	青色
 	Dark	深色
 	Darken	變暗
+	Darkness	暗度
 	dash	虛線
 	Dash Pattern	虛線樣式
 	Dashed	虛線
diff --git a/crates/ui-egui/src/panels/appearance.rs b/crates/ui-egui/src/panels/appearance.rs
index 27b3be5eb..fcafdedb5 100644
--- a/crates/ui-egui/src/panels/appearance.rs
+++ b/crates/ui-egui/src/panels/appearance.rs
@@ -724,8 +724,8 @@ fn has_options(id: &str) -> bool {
     vectorcraft_effects::default_params(id).is_some_and(|d| d.as_object().is_some_and(|o| !o.is_empty()))
 }
 
-/// Inline editor for an applied effect's parameters (numbers, booleans, strings, colours);
-/// edits go through `effect.setParams`.
+/// Inline editor for an applied effect's parameters (numbers, booleans, strings, colors, and
+/// Drop Shadow's Color or Darkness as radio buttons); edits go through `effect.setParams`.
 fn effect_editor(app: &mut VectorcraftApp, ui: &mut Ui, item: Option<usize>, k: usize, e: &Effect) {
     let t = Tokens::get(ui.ctx());
     let defaults = vectorcraft_effects::default_params(&e.id).unwrap_or(Value::Null);
@@ -755,6 +755,15 @@ fn effect_editor(app: &mut VectorcraftApp, ui: &mut Ui, item: Option<usize>, k:
                     }
                     return;
                 }
+                if e.id == "stylize.dropShadow" && key == "shade" {
+                    let cur = v.as_str().unwrap_or_default();
+                    for (label, value) in crate::dialogs::SHADES {
+                        if widgets::radio(ui, label, cur.eq_ignore_ascii_case(value), true) && !cur.eq_ignore_ascii_case(value) {
+                            change = Some((key.clone(), json!(value)));
+                        }
+                    }
+                    return;
+                }
                 match v {
                     Value::Bool(b) => {
                         if widgets::check(ui, "", *b, true) {
@@ -980,6 +989,46 @@ mod tests {
         assert_eq!(shown_effect_label("plugin.example.glow"), effect_label("plugin.example.glow"));
     }
 
+    /// A Drop Shadow's inline editor has Color and Darkness as radio buttons in its Shade row; a
+    /// click on Darkness sets the effect's `shade`.
+    #[test]
+    fn the_drop_shadow_editor_chooses_color_or_darkness() {
+        let mut app = VectorcraftApp::new(vectorcraft_engine::Session::new(), Default::default());
+        app.run("file.new", json!({"width": 100, "height": 100})).unwrap();
+        let id = app.run("shape.rectangle", json!({"x": 0, "y": 0, "width": 20, "height": 20})).unwrap()["id"].as_u64().unwrap();
+        app.run("effect.apply", json!({"effect": "stylize.dropShadow"})).unwrap();
+        let ctx = egui::Context::default();
+        crate::theme::install_fonts(&ctx);
+        set_pstate(&ctx, "ap-fx-open-None-0", true);
+        let mut time = 0.0;
+        let mut run = |app: &mut VectorcraftApp, events: Vec<egui::Event>| {
+            time += 0.1;
+            let mut out = ctx.run_ui(egui::RawInput { events, time: Some(time), ..Default::default() }, |ui| show(app, ui));
+            out.textures_delta.clear();
+            out
+        };
+        run(&mut app, vec![]);
+        let out = run(&mut app, vec![]);
+        // The Shade row's Darkness, below the Darkness value's own row.
+        fn find(s: &egui::Shape, out: &mut Vec<egui::Pos2>) {
+            match s {
+                egui::Shape::Text(t) if t.galley.text() == "Darkness" => out.push(t.visual_bounding_rect().center()),
+                egui::Shape::Vec(v) => v.iter().for_each(|s| find(s, out)),
+                _ => {}
+            }
+        }
+        let mut found = vec![];
+        out.shapes.iter().for_each(|c| find(&c.shape, &mut found));
+        assert_eq!(found.len(), 2, "{found:?}");
+        let at = found.into_iter().max_by(|a, b| a.y.total_cmp(&b.y)).unwrap();
+        let button = |pressed| egui::Event::PointerButton { pos: at, button: egui::PointerButton::Primary, pressed, modifiers: Default::default() };
+        for events in [vec![egui::Event::PointerMoved(at)], vec![button(true)], vec![button(false)]] {
+            run(&mut app, events);
+        }
+        let n = app.session.doc().unwrap().doc.node(NodeId(id)).unwrap().clone();
+        assert_eq!(n.appearance.effects[0].params["shade"], json!("darkness"));
+    }
+
     #[test]
     fn drops_pick_the_command() {
         use vectorcraft_doc::{Appearance, FillLayer};
diff --git a/docs/target-app-parity.md b/docs/target-app-parity.md
index c0ab119f7..56d685c69 100644
--- a/docs/target-app-parity.md
+++ b/docs/target-app-parity.md
@@ -578,6 +578,8 @@ Moved from the ROADMAP's "Shipped so far" on 2026-10-10. Update it when a featur
 
 - **Raster effects after document and view changes:** a cached drop shadow, outer glow or filtered content is made again when something its content reads from outside the object changes: a pattern's art or tiling, a symbol shown inside another symbol, a brush definition, an image's pixels, the raster resolution (De-Interlace), Page Knockout Group, Document Setup's substitution highlights, a layer's Dim Images, the color settings, the fonts, Pixel Preview, Anti-aliased Artwork, Overprint Preview and isolation mode. A thumbnail under Color Halftone or Mezzotint is made again when the document's color mode changes. Raster effects (blur, shadow, glow, grain) drawn after a pattern, radial or freeform gradient fill export at their place and size (#1541, fixes #1536).
 
+- **Drop Shadow's Darkness:** Effect › Stylize › Drop Shadow… has Color and Darkness as radio buttons, each with its field, and the Appearance panel's inline editor has the two radio buttons in its Shade row (`shade`: `color` or `darkness`; `darkness`: 0 to 100%, 100 by default). Color is the default, and a shadow saved without these keys draws as before. With Darkness the shadow is the object's own colors with black added: in a CMYK document their cyan, magenta and yellow stay and their black K becomes K + darkness × (1 − K), and in an RGB document each channel is multiplied by 1 − darkness. Darkness 0% gives the object's color; 100% gives black in an RGB document and keeps the colors under 100% black in a CMYK one. SVG export writes the object blurred, moved and darkened with `feComponentTransfer` (screen colors, in a CMYK document too), and SVG import reads it back; CSS export leaves the shadow out and marks the object unsupported. Behavior reference: Illustrator CC Help (2014, [PDF](https://help.adobe.com/archive/en/illustrator/cc/2014/illustrator_reference.pdf)), page 428 (PDF page 434).
+
 - **Live objects after document changes:** a blend, envelope or repeat, with or without an effect of its own, is evaluated again when one of these changes: the tiling of a pattern whose tiles an envelope bends (Distort Pattern Fills), a symbol shown inside a symbol, a pattern or an opacity mask, the fonts of its type, a placed document's file once the file is read, and the color settings. A gradient mesh, with or without an effect of its own, is colored again when the color settings change.
 
 - **Full font names (#1258):** OpenType name ID 4 identifies its face alongside family/legacy/PostScript names, including localized names, for loaded fonts, cataloged files and Missing Fonts searches. Synthetic name-table regressions cover full names distinct from their PostScript name, real-family precedence and variable fonts' default faces. Windows font-service activation remains unverified; scores and hours are unchanged.