Feature flag raster image formats (#50)

## Notes

- Fixes #47
- Allows support for raster images to be completely disabled as well as
flagging individual formats (allows the `image` dependency to be
disabled entirely as `image` is surprisingly large even with no formats
enabled)

---------

Signed-off-by: Nico Burns <nico@nicoburns.com>

CHANGELOG.md

@@ -15,6 +15,10 @@ You can find its changes [documented below](#050-2024-11-20).
 
 This release has an [MSRV][] of 1.75.
 
+### Changed
+
+- Feature flag raster image formats (enabled by default) ([#50] by [@nicoburns])
+
 ## [0.5.0][] (2024-11-20)
 
 This release has an [MSRV][] of 1.75.
@@ -107,6 +111,7 @@ This release has an [MSRV][] of 1.75.
 [@MarijnS95]: https://github.com/MarijnS95
 [@DasLixou]: https://github.com/DasLixou
 
+[#50]: https://github.com/linebender/vello_svg/pull/50
 [#42]: https://github.com/linebender/vello_svg/pull/42
 [#34]: https://github.com/linebender/vello_svg/pull/34
 [#31]: https://github.com/linebender/vello_svg/pull/31

Cargo.toml

@@ -99,16 +99,17 @@ workspace = true
 vello = { workspace = true }
 thiserror = "1.0.69"
 usvg = "0.44.0"
-image = { version = "0.25.5", default-features = false, features = [
-  "webp",
-  "png",
-  "jpeg",
-  "gif",
-] }
+image = { version = "0.25.5", default-features = false, features = [ "webp", "png", "jpeg", "gif"], optional = true }
 
 [target.'cfg(target_arch = "wasm32")'.dev-dependencies]
 wasm-bindgen-test = "0.3.49"
 
 [features]
+default = ["image_format_png", "image_format_gif", "image_format_jpeg", "image_format_webp"]
 # Enables the wgpu feature on vello, which is disabled by default
 wgpu = ["vello/wgpu"]
+image = ["dep:image"]
+image_format_png = ["image", "image/png"]
+image_format_jpeg = ["image", "image/jpeg"]
+image_format_gif = ["image", "image/gif"]
+image_format_webp = ["image", "image/webp"]

src/render.rs

@@ -104,13 +104,23 @@ pub(crate) fn render_group<F: FnMut(&mut Scene, &usvg::Node)>(
                     | usvg::ImageKind::PNG(_)
                     | usvg::ImageKind::GIF(_)
                     | usvg::ImageKind::WEBP(_) => {
-                        let Ok(decoded_image) = util::decode_raw_raster_image(img.kind()) else {
+                        #[cfg(feature = "image")]
+                        {
+                            let Ok(decoded_image) = util::decode_raw_raster_image(img.kind())
+                            else {
+                                error_handler(scene, node);
+                                continue;
+                            };
+                            let image = util::into_image(decoded_image);
+                            let image_ts = util::to_affine(&img.abs_transform());
+                            scene.draw_image(&image, image_ts);
+                        }
+
+                        #[cfg(not(feature = "image"))]
+                        {
                             error_handler(scene, node);
                             continue;
-                        };
-                        let image = util::into_image(decoded_image);
-                        let image_ts = util::to_affine(&img.abs_transform());
-                        scene.draw_image(&image, image_ts);
+                        }
                     }
                     usvg::ImageKind::SVG(svg) => {
                         render_group(scene, svg.root(), transform, error_handler);

src/util.rs

@@ -2,9 +2,12 @@
 // SPDX-License-Identifier: Apache-2.0 OR MIT
 
 use vello::kurbo::{Affine, BezPath, Point, Rect, Stroke};
-use vello::peniko::{Blob, Brush, Color, Fill, Image};
+use vello::peniko::{Brush, Color, Fill};
 use vello::Scene;
 
+#[cfg(feature = "image")]
+use vello::peniko::{Blob, Image};
+
 pub fn to_affine(ts: &usvg::Transform) -> Affine {
     let usvg::Transform {
         sx,
@@ -89,6 +92,7 @@ pub fn to_bez_path(path: &usvg::Path) -> BezPath {
     local_path
 }
 
+#[cfg(feature = "image")]
 pub fn into_image(image: image::ImageBuffer<image::Rgba<u8>, Vec<u8>>) -> Image {
     let (width, height) = (image.width(), image.height());
     let image_data: Vec<u8> = image.into_vec();
@@ -202,24 +206,21 @@ pub fn default_error_handler(scene: &mut Scene, node: &usvg::Node) {
     );
 }
 
+#[cfg(feature = "image")]
 pub fn decode_raw_raster_image(
     img: &usvg::ImageKind,
 ) -> Result<image::RgbaImage, image::ImageError> {
-    let res = match img {
-        usvg::ImageKind::JPEG(data) => {
-            image::load_from_memory_with_format(data, image::ImageFormat::Jpeg)
-        }
-        usvg::ImageKind::PNG(data) => {
-            image::load_from_memory_with_format(data, image::ImageFormat::Png)
-        }
-        usvg::ImageKind::GIF(data) => {
-            image::load_from_memory_with_format(data, image::ImageFormat::Gif)
-        }
-        usvg::ImageKind::WEBP(data) => {
-            image::load_from_memory_with_format(data, image::ImageFormat::WebP)
-        }
+    // All `image::ImageFormat` variants exist even if the feature in the image crate is disabled,
+    // but `image::load_from_memory_with_format` will fail with an Unsupported error if the
+    // image crate feature flag is disabled. So we don't need any of our own feature handling here.
+    let (data, format) = match img {
+        usvg::ImageKind::JPEG(data) => (data, image::ImageFormat::Jpeg),
+        usvg::ImageKind::PNG(data) => (data, image::ImageFormat::Png),
+        usvg::ImageKind::GIF(data) => (data, image::ImageFormat::Gif),
+        usvg::ImageKind::WEBP(data) => (data, image::ImageFormat::WebP),
         usvg::ImageKind::SVG(_) => unreachable!(),
-    }?
-    .into_rgba8();
-    Ok(res)
+    };
+
+    let dyn_image = image::load_from_memory_with_format(data, format)?;
+    Ok(dyn_image.into_rgba8())
 }