Add support for embedded luma JPEG images (#850)

crates/resvg/src/image.rs

@@ -86,7 +86,25 @@ mod raster_images {
 
         let options = DecoderOptions::default().jpeg_set_out_colorspace(ColorSpace::RGBA);
         let mut decoder = zune_jpeg::JpegDecoder::new_with_options(data, options);
-        let img_data = decoder.decode().ok()?;
+        decoder.decode_headers().ok()?;
+        let output_cs = decoder.get_output_colorspace()?;
+
+        let img_data = {
+            let data = decoder.decode().ok()?;
+            match output_cs {
+                ColorSpace::RGBA => data,
+                // `set_output_color_space` is not guaranteed to actually always set the output space
+                // to RGBA (its docs say "we do not guarantee the decoder can convert to all colorspaces").
+                // In particular, it seems like it doesn't work for luma JPEGs,
+                // so we convert them manually.
+                ColorSpace::Luma => data
+                    .into_iter()
+                    .flat_map(|p| [p, p, p, 255])
+                    .collect::<Vec<_>>(),
+                _ => return None,
+            }
+        };
+
         let info = decoder.info()?;
 
         let size = tiny_skia::IntSize::from_wh(info.width as u32, info.height as u32)?;

crates/resvg/tests/integration/render.rs

@@ -1101,7 +1101,9 @@ use crate::render;
 #[test] fn structure_image_embedded_gif() { assert_eq!(render("tests/structure/image/embedded-gif"), 0); }
 #[test] fn structure_image_embedded_jpeg_as_image_jpeg() { assert_eq!(render("tests/structure/image/embedded-jpeg-as-image-jpeg"), 0); }
 #[test] fn structure_image_embedded_jpeg_as_image_jpg() { assert_eq!(render("tests/structure/image/embedded-jpeg-as-image-jpg"), 0); }
+#[test] fn structure_image_embedded_jpeg_luma() { assert_eq!(render("tests/structure/image/embedded-jpeg-luma"), 0); }
 #[test] fn structure_image_embedded_jpeg_without_mime() { assert_eq!(render("tests/structure/image/embedded-jpeg-without-mime"), 0); }
+#[test] fn structure_image_embedded_png_luma() { assert_eq!(render("tests/structure/image/embedded-png-luma"), 0); }
 #[test] fn structure_image_embedded_png() { assert_eq!(render("tests/structure/image/embedded-png"), 0); }
 #[test] fn structure_image_embedded_svg_with_text() { assert_eq!(render("tests/structure/image/embedded-svg-with-text"), 0); }
 #[test] fn structure_image_embedded_svg_without_mime() { assert_eq!(render("tests/structure/image/embedded-svg-without-mime"), 0); }