Add support for additional image-rendering attributes (#833)

Closes #828

crates/resvg/src/image.rs

@@ -57,6 +57,7 @@ fn render_vector(
 #[cfg(feature = "raster-images")]
 mod raster_images {
     use crate::OptionLog;
+    use usvg::ImageRendering;
 
     fn decode_raster(image: &usvg::ImageKind) -> Option<tiny_skia::Pixmap> {
         match image {
@@ -169,10 +170,14 @@ mod raster_images {
         let rect = tiny_skia::Size::from_wh(raster.width() as f32, raster.height() as f32)?
             .to_rect(0.0, 0.0)?;
 
-        let mut quality = tiny_skia::FilterQuality::Bicubic;
-        if rendering_mode == usvg::ImageRendering::OptimizeSpeed {
-            quality = tiny_skia::FilterQuality::Nearest;
-        }
+        let quality = match rendering_mode {
+            ImageRendering::OptimizeQuality => tiny_skia::FilterQuality::Bicubic,
+            ImageRendering::OptimizeSpeed => tiny_skia::FilterQuality::Nearest,
+            ImageRendering::Smooth => tiny_skia::FilterQuality::Bilinear,
+            ImageRendering::HighQuality => tiny_skia::FilterQuality::Bicubic,
+            ImageRendering::CrispEdges => tiny_skia::FilterQuality::Nearest,
+            ImageRendering::Pixelated => tiny_skia::FilterQuality::Nearest,
+        };
 
         let pattern = tiny_skia::Pattern::new(
             raster.as_ref(),

crates/resvg/src/main.rs

@@ -162,7 +162,7 @@ OPTIONS:
                                 geometricPrecision]
   --image-rendering HINT        Selects the default image rendering method
                                 [default: optimizeQuality]
-                                [possible values: optimizeQuality, optimizeSpeed]
+                                [possible values: optimizeQuality, optimizeSpeed, smooth, high-quality, crisp-edges, pixelated]
   --resources-dir DIR           Sets a directory that will be used during
                                 relative paths resolving.
                                 Expected to be the same as the directory that

crates/resvg/tests/integration/render.rs

@@ -740,6 +740,7 @@ use crate::render;
 #[test] fn painting_fill_opacity_with_pattern() { assert_eq!(render("tests/painting/fill-opacity/with-pattern"), 0); }
 #[test] fn painting_fill_rule_evenodd() { assert_eq!(render("tests/painting/fill-rule/evenodd"), 0); }
 #[test] fn painting_fill_rule_nonzero() { assert_eq!(render("tests/painting/fill-rule/nonzero"), 0); }
+#[test] fn painting_image_rendering_high_quality() { assert_eq!(render("tests/painting/image-rendering/high-quality"), 0); }
 #[test] fn painting_image_rendering_on_feImage() { assert_eq!(render("tests/painting/image-rendering/on-feImage"), 0); }
 #[test] fn painting_image_rendering_optimizeSpeed_on_SVG() { assert_eq!(render("tests/painting/image-rendering/optimizeSpeed-on-SVG"), 0); }
 #[test] fn painting_image_rendering_optimizeSpeed() { assert_eq!(render("tests/painting/image-rendering/optimizeSpeed"), 0); }

crates/usvg/src/main.rs

@@ -43,7 +43,7 @@ OPTIONS:
                                     geometricPrecision]
   --image-rendering HINT            Selects the default image rendering method
                                     [default: optimizeQuality]
-                                    [possible values: optimizeQuality, optimizeSpeed]
+                                    [possible values: optimizeQuality, optimizeSpeed, smooth, high-quality, crisp-edges, pixelated]
   --resources-dir DIR               Sets a directory that will be used during
                                     relative paths resolving.
                                     Expected to be the same as the directory that

crates/usvg/src/parser/svgtree/mod.rs

@@ -1020,6 +1020,10 @@ impl<'a, 'input: 'a> FromValue<'a, 'input> for ImageRendering {
         match value {
             "auto" | "optimizeQuality" => Some(ImageRendering::OptimizeQuality),
             "optimizeSpeed" => Some(ImageRendering::OptimizeSpeed),
+            "smooth" => Some(ImageRendering::Smooth),
+            "high-quality" => Some(ImageRendering::HighQuality),
+            "crisp-edges" => Some(ImageRendering::CrispEdges),
+            "pixelated" => Some(ImageRendering::Pixelated),
             _ => None,
         }
     }

crates/usvg/src/parser/svgtree/parse.rs

@@ -242,6 +242,13 @@ pub(crate) fn parse_svg_element<'input>(
         // For some reason those properties are allowed only inside a `style` attribute and CSS.
         if matches!(aid, AId::MixBlendMode | AId::Isolation | AId::FontKerning) {
             continue;
+        } else if aid == AId::ImageRendering
+            && matches!(
+                attr.value(),
+                "smooth" | "high-quality" | "crisp-edges" | "pixelated"
+            )
+        {
+            continue;
         }
 
         append_attribute(parent_id, tag_name, aid, attr.value_storage().clone(), doc);

crates/usvg/src/tree/mod.rs

@@ -170,6 +170,11 @@ impl std::str::FromStr for TextRendering {
 pub enum ImageRendering {
     OptimizeQuality,
     OptimizeSpeed,
+    // The following can only appear as presentation attributes.
+    Smooth,
+    HighQuality,
+    CrispEdges,
+    Pixelated,
 }
 
 impl Default for ImageRendering {
@@ -185,6 +190,10 @@ impl std::str::FromStr for ImageRendering {
         match s {
             "optimizeQuality" => Ok(ImageRendering::OptimizeQuality),
             "optimizeSpeed" => Ok(ImageRendering::OptimizeSpeed),
+            "smooth" => Ok(ImageRendering::Smooth),
+            "high-quality" => Ok(ImageRendering::HighQuality),
+            "crisp-edges" => Ok(ImageRendering::CrispEdges),
+            "pixelated" => Ok(ImageRendering::Pixelated),
             _ => Err("invalid"),
         }
     }

crates/usvg/src/writer.rs

@@ -647,6 +647,18 @@ fn write_element(node: &Node, is_clip_path: bool, opt: &WriteOptions, xml: &mut
                 ImageRendering::OptimizeSpeed => {
                     xml.write_svg_attribute(AId::ImageRendering, "optimizeSpeed");
                 }
+                ImageRendering::Smooth => {
+                    xml.write_attribute(AId::Style.to_str(), "image-rendering:smooth");
+                }
+                ImageRendering::HighQuality => {
+                    xml.write_attribute(AId::Style.to_str(), "image-rendering:high-quality");
+                }
+                ImageRendering::CrispEdges => {
+                    xml.write_attribute(AId::Style.to_str(), "image-rendering:crisp-edges");
+                }
+                ImageRendering::Pixelated => {
+                    xml.write_attribute(AId::Style.to_str(), "image-rendering:pixelated");
+                }
             }
 
             xml.write_image_data(&img.kind);

docs/svg2-changelog.md

@@ -196,7 +196,7 @@ Basically everything from [CSS Text Module Level 3](https://www.w3.org/TR/css-te
 - [x] An [`isolation`](https://www.w3.org/TR/compositing-1/#isolation) property.
 - [ ] `left`, `center` and `right` variants to `refX` and `refY` properties of the [`marker`](https://www.w3.org/TR/SVG2/painting.html#MarkerElement) element.
 - [x] An `auto-start-reverse` variant to [`orient`](https://www.w3.org/TR/SVG2/painting.html#OrientAttribute) property of the [`marker`](https://www.w3.org/TR/SVG2/painting.html#MarkerElement) element
-
+- [x] The `image-rendering` can appear as a presentation attribute with additional possible values. Currently, there is only best-effort support for "pixelated".
 ### Changed
 
 - [x] Markers can be set on all shapes and not only on `path`.