diff --git a/.gitignore b/.gitignore
index 2568b8c..a7258d0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,6 +1,11 @@
 /target
 Cargo.lock
 
+# for test
+*.ipynb
+*.jxl
+*.jpeg
+
 # Byte-compiled / optimized / DLL files
 __pycache__/
 .pytest_cache/
diff --git a/pillow_jxl/JpegXLImagePlugin.py b/pillow_jxl/JpegXLImagePlugin.py
index fdac160..d0586cc 100644
--- a/pillow_jxl/JpegXLImagePlugin.py
+++ b/pillow_jxl/JpegXLImagePlugin.py
@@ -27,7 +27,11 @@ def _open(self):
         self.fc = self.fp.read()
         self._decoder = Decoder()
 
-        self._jxlinfo, self._data = self._decoder(self.fc)
+        self.jpeg, self._jxlinfo, self._data = self._decoder(self.fc)
+        # FIXME (Isotr0py): Maybe slow down jpeg reconstruction
+        if self.jpeg:
+            with Image.open(BytesIO(self._data)) as im:
+                self._data = im.tobytes()
         self._size = (self._jxlinfo.width, self._jxlinfo.height)
         self.rawmode = self._jxlinfo.mode
         # NOTE (Isotr0py): PIL 10.1.0 changed the mode to property, use _mode instead
@@ -85,7 +89,12 @@ def _save(im, fp, filename, save_all=False):
         decoding_speed=decoding_speed,
         use_container=use_container,
     )
-    data = enc(im.tobytes(), im.width, im.height)
+    # FIXME (Isotr0py): im.filename maybe None if parse stream
+    if im.format == "JPEG" and im.filename:
+        with open(im.filename, "rb") as f:
+            data = enc(f.read(), im.width, im.height, jpeg_encode=True)
+    else:
+        data = enc(im.tobytes(), im.width, im.height, jpeg_encode=False)
     fp.write(data)
 
 
diff --git a/pillow_jxl/__init__.pyi b/pillow_jxl/__init__.pyi
index 6e94cc7..055561d 100644
--- a/pillow_jxl/__init__.pyi
+++ b/pillow_jxl/__init__.pyi
@@ -17,7 +17,16 @@ class Encoder:
                  lossless: bool = True,
                  quality: float = 0.0): ...
 
-    def __call__(self, data: bytes, width: int, height: int) -> bytes: ...
+    def __call__(self, data: bytes, width: int, height: int, jpeg_encode: bool) -> bytes: ...
+    '''
+        Encode a jpeg-xl image.
+
+        Args:
+            data(`bytes`): raw image bytes
+
+        Return:
+            `bytes`: The encoded jpeg-xl image.
+    '''
 
 
 class Decoder:
@@ -30,7 +39,7 @@ class Decoder:
 
     def __init__(self, parallel: bool = True): ...
 
-    def __call__(self, data: bytes) -> (ImageInfo, bytes): ...
+    def __call__(self, data: bytes) -> (bool, ImageInfo, bytes): ...
     '''
         Decode a jpeg-xl image.
 
@@ -38,6 +47,7 @@ class Decoder:
             data(`bytes`): jpeg-xl image
 
         Return:
+            `bool`: If the jpeg is reconstructed
             `ImageInfo`: The metadata of decoded image
             `bytes`: The decoded image.
     '''
diff --git a/src/lib.rs b/src/lib.rs
index 5beb7f2..9bbd971 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,7 +1,7 @@
 use pyo3::prelude::*;
 use pyo3::types::PyBytes;
 
-use jpegxl_rs::decode::{Metadata, Pixels};
+use jpegxl_rs::decode::{Metadata, Pixels, Data};
 use jpegxl_rs::encode::EncoderResult;
 use jpegxl_rs::parallel::threads_runner::ThreadsRunner;
 use jpegxl_rs::{decoder_builder, encoder_builder};
@@ -52,8 +52,8 @@ impl Encoder {
         }
     }
 
-    #[pyo3(signature = (data, width, height))]
-    fn __call__<'a>(&'a self, _py: Python<'a>, data: &[u8], width: u32, height: u32) -> &PyBytes {
+    #[pyo3(signature = (data, width, height, jpeg_encode))]
+    fn __call__<'a>(&'a self, _py: Python<'a>, data: &[u8], width: u32, height: u32, jpeg_encode: bool) -> &PyBytes {
         let parallel_runner: ThreadsRunner;
         let mut encoder = match self.parallel {
             true => {
@@ -71,7 +71,10 @@ impl Encoder {
         encoder.quality = self.quality;
         encoder.use_container = self.use_container;
         encoder.decoding_speed = self.decoding_speed;
-        let buffer: EncoderResult<u8> = encoder.encode(&data, width, height).unwrap();
+        let buffer: EncoderResult<u8> = match jpeg_encode {
+            true => encoder.encode_jpeg(&data).unwrap(),
+            false => encoder.encode(&data, width, height).unwrap(),
+        };
         PyBytes::new(_py, &buffer.data)
     }
 
@@ -133,7 +136,7 @@ impl Decoder {
     }
 
     #[pyo3(signature = (data))]
-    fn __call__<'a>(&'a self, _py: Python<'a>, data: &[u8]) -> (ImageInfo, &PyBytes) {
+    fn __call__<'a>(&'a self, _py: Python<'a>, data: &[u8]) -> (bool, ImageInfo, &PyBytes) {
         let parallel_runner: ThreadsRunner;
         let decoder = match self.parallel {
             true => {
@@ -145,12 +148,13 @@ impl Decoder {
             }
             false => decoder_builder().build().unwrap(),
         };
-        let (info, img) = decoder.decode(&data).unwrap();
-        let img: Vec<u8> = match img {
-            Pixels::Uint8(x) => x,
+        let (info, img) = decoder.reconstruct(&data).unwrap();
+        let (jpeg, img) = match img {
+            Data::Jpeg(x) => (true, x),
+            Data::Pixels(Pixels::Uint8(x)) => (false, x),
             _ => panic!("Unsupported dtype for decoding"),
         };
-        (ImageInfo::from(info), PyBytes::new(_py, &img))
+        (jpeg, ImageInfo::from(info), PyBytes::new(_py, &img))
     }
 
     fn __repr__(&self) -> PyResult<String> {