Fix rendering of filters with skews and rotations

CHANGELOG.md

@@ -22,6 +22,9 @@ This changelog also contains important changes in dependencies.
 - Incorrect transform order on the outermost `svg` element with a `viewBox`. (#899)
 - Relative positioning of right-to-left text with `dx` and `dy`, including text on a path and text decorations. (#1093)
 - `text-anchor` now uses the actual extent of a text chunk, which `dx` and `textLength` can change. (#1145)
+- Filters inside rotated or skewed groups are now applied in the user space of the group.
+  This fixes the clipping to filter regions and subregions, as well as the direction of
+  offsets, blurs, turbulence and tiles, and the rendering of `feImage`. (#949)
 
 ## [0.48.1] 2026-08-02
 

crates/resvg/src/render.rs

@@ -59,6 +59,50 @@ fn render_group(
         return Some(());
     }
 
+    let rest = if group.filters().is_empty() {
+        tiny_skia::Transform::identity()
+    } else {
+        let sx = transform.sx.hypot(transform.ky);
+        let sy = transform.kx.hypot(transform.sy);
+        tiny_skia::Transform::from_row(
+            transform.sx / sx,
+            transform.ky / sx,
+            transform.kx / sy,
+            transform.sy / sy,
+            0.0,
+            0.0,
+        )
+    };
+    let inv_rest = rest.invert()?;
+
+    let max_bbox = ctx.max_bbox.to_rect().transform(inv_rest)?.round_out()?;
+    let (layer, ibbox) =
+        render_layer(group, &Context { max_bbox }, inv_rest.pre_concat(transform))?;
+
+    let paint = tiny_skia::Paint {
+        shader: tiny_skia::Pattern::new(
+            layer.as_ref(),
+            tiny_skia::SpreadMode::Pad,
+            tiny_skia::FilterQuality::Bilinear,
+            group.opacity().get(),
+            tiny_skia::Transform::from_translate(ibbox.x() as f32, ibbox.y() as f32),
+        ),
+        blend_mode: convert_blend_mode(group.blend_mode()),
+        anti_alias: true,
+        ..tiny_skia::Paint::default()
+    };
+    let path = tiny_skia::PathBuilder::from_rect(ibbox.to_rect());
+    pixmap.fill_path(&path, &paint, tiny_skia::FillRule::Winding, rest, None);
+
+    Some(())
+}
+
+/// Renders an isolated group into a new layer, returning it and its position.
+fn render_layer(
+    group: &usvg::Group,
+    ctx: &Context,
+    transform: tiny_skia::Transform,
+) -> Option<(tiny_skia::Pixmap, tiny_skia::IntRect)> {
     let bbox = group.layer_bounding_box().transform(transform)?;
 
     let mut ibbox = if group.filters().is_empty() {
@@ -124,22 +168,7 @@ fn render_group(
         crate::mask::apply(mask, ctx, transform, &mut sub_pixmap);
     }
 
-    let paint = tiny_skia::PixmapPaint {
-        opacity: group.opacity().get(),
-        blend_mode: convert_blend_mode(group.blend_mode()),
-        quality: tiny_skia::FilterQuality::Nearest,
-    };
-
-    pixmap.draw_pixmap(
-        ibbox.x(),
-        ibbox.y(),
-        sub_pixmap.as_ref(),
-        &paint,
-        tiny_skia::Transform::identity(),
-        None,
-    );
-
-    Some(())
+    Some((sub_pixmap, ibbox))
 }
 
 pub fn convert_blend_mode(mode: usvg::BlendMode) -> tiny_skia::BlendMode {

crates/resvg/tests/integration/render.rs

@@ -348,13 +348,15 @@ use crate::render;
 #[test] fn filters_filter_with_multiple_transforms_1() { assert_eq!(render("tests/filters/filter/with-multiple-transforms-1"), 0); }
 #[test] fn filters_filter_with_multiple_transforms_2() { assert_eq!(render("tests/filters/filter/with-multiple-transforms-2"), 0); }
 #[test] fn filters_filter_with_region_and_filterUnits_eq_userSpaceOnUse() { assert_eq!(render("tests/filters/filter/with-region-and-filterUnits=userSpaceOnUse"), 0); }
+#[test] fn filters_filter_with_region_and_skew_on_intermediate_result() { assert_eq!(render("tests/filters/filter/with-region-and-skew-on-intermediate-result"), 0); }
 #[test] fn filters_filter_with_region_and_subregion() { assert_eq!(render("tests/filters/filter/with-region-and-subregion"), 0); }
 #[test] fn filters_filter_with_region_outside_the_canvas() { assert_eq!(render("tests/filters/filter/with-region-outside-the-canvas"), 0); }
 #[test] fn filters_filter_with_region_outside_the_viewbox() { assert_eq!(render("tests/filters/filter/with-region-outside-the-viewbox"), 0); }
 #[test] fn filters_filter_with_region() { assert_eq!(render("tests/filters/filter/with-region"), 0); }
 #[test] fn filters_filter_with_subregion_1() { assert_eq!(render("tests/filters/filter/with-subregion-1"), 0); }
 #[test] fn filters_filter_with_subregion_2() { assert_eq!(render("tests/filters/filter/with-subregion-2"), 0); }
 #[test] fn filters_filter_with_subregion_3() { assert_eq!(render("tests/filters/filter/with-subregion-3"), 0); }
+#[test] fn filters_filter_with_subregion_and_rotation() { assert_eq!(render("tests/filters/filter/with-subregion-and-rotation"), 0); }
 #[test] fn filters_filter_with_transform_outside_of_canvas() { assert_eq!(render("tests/filters/filter/with-transform-outside-of-canvas"), 0); }
 #[test] fn filters_filter_without_region_and_filterUnits_eq_userSpaceOnUse() { assert_eq!(render("tests/filters/filter/without-region-and-filterUnits=userSpaceOnUse"), 0); }
 #[test] fn filters_filter_zero_sized_subregion() { assert_eq!(render("tests/filters/filter/zero-sized-subregion"), 0); }