SVG import: support feBlend filter primitive and transparent backdrops

crates/svg/src/import/fx.rs

@@ -2,7 +2,8 @@
 //! 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 color matrix, composite, merge), the object moved and
+//! shadow chains (offset, blur, flood or color matrix, composite, merge), blur and shadow graphs
+//! with `feBlend` and transparent backdrops (as exported by Figma and others), 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.
 
@@ -197,15 +198,52 @@ fn eval(f: &Filter, k: f64) -> Option<V> {
             }
             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::Blend(b) => {
+                let (a, b_in) = (input(b.input1())?, input(b.input2())?);
+                let transparent = |v: &V| matches!(v, V::Flood(_, o) if *o <= 1e-6);
+                if transparent(&b_in) {
+                    a
+                } else if transparent(&a) {
+                    b_in
+                } else if b.mode() == usvg::BlendMode::Normal {
+                    V::Stack(b_in.layers().into_iter().chain(a.layers()).collect())
+                } else {
+                    return None;
+                }
+            }
             Kind::Composite(c) => {
                 let (a, b) = (input(c.input1())?, input(c.input2())?);
+                let transparent = |v: &V| matches!(v, V::Flood(_, o) if *o <= 1e-6);
                 match c.operator() {
                     CompositeOperator::In => a.inside(b)?,
-                    CompositeOperator::Over => V::Stack(b.layers().into_iter().chain(a.layers()).collect()),
+                    CompositeOperator::Over => {
+                        if transparent(&b) {
+                            a
+                        } else if transparent(&a) {
+                            b
+                        } else {
+                            V::Stack(b.layers().into_iter().chain(a.layers()).collect())
+                        }
+                    }
                     _ => return None,
                 }
             }
-            Kind::Merge(m) => V::Stack(m.inputs().iter().map(input).collect::<Option<Vec<_>>>()?.into_iter().flat_map(V::layers).collect()),
+            Kind::Merge(m) => {
+                let mut layers: Vec<V> = m
+                    .inputs()
+                    .iter()
+                    .map(input)
+                    .collect::<Option<Vec<_>>>()?
+                    .into_iter()
+                    .flat_map(V::layers)
+                    .filter(|v| !matches!(v, V::Flood(_, o) if *o <= 1e-6))
+                    .collect();
+                match layers.len() {
+                    0 => return None,
+                    1 => layers.remove(0),
+                    _ => V::Stack(layers),
+                }
+            }
             Kind::ColorMatrix(c) => match c.kind() {
                 ColorMatrixKind::Matrix(m) => input(c.input())?.color_matrix(m)?,
                 _ => return None,

crates/svg/tests/import_live.rs

@@ -164,6 +164,57 @@ fn an_instances_shadow_filter_and_the_art_export_cover_its_symbols_art() {
     assert!((*xf * Point::ORIGIN).distance(Point::ORIGIN) < 1e-9, "{svg}");
 }
 
+#[test]
+fn a_figma_blurred_shape_filter_becomes_gaussian_blur() {
+    let (d, w) = open(
+        r##"<defs><filter id="b"><feFlood flood-opacity="0" result="BackgroundImageFix"/><feBlend in="SourceGraphic" in2="BackgroundImageFix" result="shape"/><feGaussianBlur result="effect1_foregroundBlur" stdDeviation="3"/></filter></defs><rect x="50" y="30" width="60" height="40" fill="#08f" filter="url(#b)"/>"##,
+    );
+    assert!(w.is_empty(), "{w:?}");
+    let fx = effects(&d);
+    assert_eq!(fx.len(), 1);
+    assert_eq!((fx[0].id.as_str(), &fx[0].params), ("blur.gaussian", &json!({"radius": 6.0})));
+}
+
+#[test]
+fn figma_blurred_shapes_inside_mask_import_with_effects_and_no_warnings() {
+    let body = r##"<mask id="m"><circle cx="50" cy="50" r="40" fill="#fff"/></mask>
+        <g mask="url(#m)">
+            <g filter="url(#b1)"><circle cx="30" cy="30" r="20" fill="#ff0"/></g>
+            <g filter="url(#b2)"><circle cx="70" cy="70" r="20" fill="#00f"/></g>
+        </g>
+        <defs>
+            <filter id="b1"><feFlood flood-opacity="0" result="BackgroundImageFix"/><feBlend in="SourceGraphic" in2="BackgroundImageFix" result="shape"/><feGaussianBlur result="effect1_foregroundBlur" stdDeviation="2"/></filter>
+            <filter id="b2"><feFlood flood-opacity="0" result="BackgroundImageFix"/><feBlend in="SourceGraphic" in2="BackgroundImageFix" result="shape"/><feGaussianBlur result="effect1_foregroundBlur" stdDeviation="4"/></filter>
+        </defs>"##;
+    let (d, w) = open(body);
+    assert!(w.is_empty(), "{w:?}");
+    let mut blurs = vec![];
+    d.walk(|n| {
+        for e in &n.appearance.effects {
+            if e.id == "blur.gaussian" {
+                blurs.push(e.params["radius"].as_f64().unwrap());
+            }
+        }
+    });
+    assert_eq!(blurs, vec![4.0, 8.0]);
+
+    let path = std::path::Path::new("/home/deck/Pictures/ícones e figurinhas/antigravity-color.svg");
+    if path.exists() {
+        let svg = std::fs::read_to_string(path).unwrap();
+        let (d, w) = import_with_report(&svg).unwrap();
+        assert!(w.is_empty(), "{w:?}");
+        let mut count = 0;
+        d.walk(|n| {
+            for e in &n.appearance.effects {
+                if e.id == "blur.gaussian" {
+                    count += 1;
+                }
+            }
+        });
+        assert_eq!(count, 11);
+    }
+}
+
 #[test]
 fn a_gaussian_blur_becomes_the_effect_with_its_radius() {
     let (d, w) = open(