Expose zune-jpeg's Exif chunk extraction (#2291)

src/codecs/jpeg/decoder.rs

@@ -69,6 +69,12 @@ impl<R: BufRead + Seek> ImageDecoder for JpegDecoder<R> {
         Ok(decoder.icc_profile())
     }
 
+    fn exif_metadata(&mut self) -> ImageResult<Option<Vec<u8>>> {
+        let mut decoder = zune_jpeg::JpegDecoder::new(&self.input);
+        decoder.decode_headers().map_err(ImageError::from_jpeg)?;
+        Ok(decoder.exif().cloned())
+    }
+
     fn read_image(self, buf: &mut [u8]) -> ImageResult<()> {
         let advertised_len = self.total_bytes();
         let actual_len = buf.len() as u64;

src/image.rs

@@ -628,6 +628,14 @@ pub trait ImageDecoder {
         Ok(None)
     }
 
+    /// Returns the raw [Exif](https://en.wikipedia.org/wiki/Exif) chunk, if it is present.
+    /// A third-party crate such as [`kamadak-exif`](https://docs.rs/kamadak-exif/) is required to actually parse it.
+    ///
+    /// For formats that don't support embedded profiles this function should always return `Ok(None)`.
+    fn exif_metadata(&mut self) -> ImageResult<Option<Vec<u8>>> {
+        Ok(None)
+    }
+
     /// Returns the total number of bytes in the decoded image.
     ///
     /// This is the size of the buffer that must be passed to `read_image` or
@@ -710,6 +718,9 @@ impl<T: ?Sized + ImageDecoder> ImageDecoder for Box<T> {
     fn icc_profile(&mut self) -> ImageResult<Option<Vec<u8>>> {
         (**self).icc_profile()
     }
+    fn exif_metadata(&mut self) -> ImageResult<Option<Vec<u8>>> {
+        (**self).exif_metadata()
+    }
     fn total_bytes(&self) -> u64 {
         (**self).total_bytes()
     }