1 files changed, 71 insertions, 0 deletions
diff --git a/src/image/svg.rs b/src/image/svg.rs
new file mode 100644
index 0000000..c2347a0
--- /dev/null
+++ b/src/image/svg.rs
@@ -0,0 +1,71 @@
+use {
+    crate::{
+        errors::SvgError,
+    },
+    image::{
+        DynamicImage,
+        RgbaImage,
+    },
+    std::path::PathBuf,
+    usvg::ScreenSize,
+    usvg_text_layout::{fontdb, TreeTextToPath},
+};
+
+fn compute_zoom(width:u32, height:u32, max_width:u32, max_height:u32) -> Result<f32, SvgError> {
+    let w: f32 = width as f32;
+    let h: f32 = height as f32;
+    let mw: f32 = max_width.max(2) as f32;
+    let mh: f32 = max_height.max(2) as f32;
+    let zoom = 1.0f32
+        .min(mw / w)
+        .min(mh / h);
+    if zoom > 0.0f32 {
+        Ok(zoom)
+    } else {
+        Err(SvgError::Internal { message: "invalid SVG dimensions" })
+    }
+}
+
+/// Generate a bitmap at the natural dimensions of the SVG unless it's too big
+///  in which case a smaller one is generated to fit into (max_width x max_height).
+pub fn render<P: Into<PathBuf>>(
+    path: P,
+    max_width: u32,
+    max_height: u32,
+) -> Result<DynamicImage, SvgError> {
+    let path: PathBuf = path.into();
+    let mut opt = usvg::Options::default();
+    opt.resources_dir = Some(path.clone());
+    let mut fontdb = fontdb::Database::new();
+    fontdb.load_system_fonts();
+    let svg_data = std::fs::read(path)?;
+    let mut tree = usvg::Tree::from_data(&svg_data, &opt)?;
+    debug!("SVG natural size: {} x {}", tree.size.width(), tree.size.height());
+    let px_size = tree.size.to_screen_size();
+    let zoom = compute_zoom(px_size.width(), px_size.height(), max_width, max_height)?;
+    debug!("svg rendering zoom: {zoom}");
+    let Some(px_size) = ScreenSize::new(
+        (px_size.width() as f32 * zoom) as u32,
+        (px_size.height() as f32 * zoom) as u32,
+    ) else {
+        return Err(SvgError::Internal { message: "invalid SVG dimensions" });
+    };
+    debug!("px_size: {px_size:?}");
+    tree.convert_text(&fontdb, opt.keep_named_groups);
+    let mut pixmap = tiny_skia::Pixmap::new(
+        px_size.width(),
+        px_size.height(),
+    ).ok_or(SvgError::Internal { message: "unable to create pixmap buffer" })?;
+    resvg::render(
+        &tree,
+        usvg::FitTo::Zoom(zoom),
+        tiny_skia::Transform::default(),
+        pixmap.as_mut(),
+    ).ok_or(SvgError::Internal { message: "resvg doesn't look happy (not sure)" })?;
+    let image_buffer = RgbaImage::from_vec(
+        pixmap.width(),
+        pixmap.height(),
+        pixmap.take(),
+    ).ok_or(SvgError::Internal { message: "wrong image buffer size" })?;
+    Ok(DynamicImage::ImageRgba8(image_buffer))
+}