Added writing XMP bytes to JPEG

Tests/test_file_jpeg.py

@@ -991,6 +991,13 @@ class TestFileJpeg:
             else:
                 assert im.getxmp() == {"xmpmeta": None}
 
+    def test_save_xmp(self, tmp_path: Path) -> None:
+        f = str(tmp_path / "temp.jpg")
+        hopper().save(f, xmp=b"XMP test")
+
+        with Image.open(f) as reloaded:
+            assert reloaded.info["xmp"] == b"XMP test"
+
     @pytest.mark.timeout(timeout=1)
     def test_eof(self) -> None:
         # Even though this decoder never says that it is finished

src/PIL/JpegImagePlugin.py

@@ -746,6 +746,11 @@ def _save(im: Image.Image, fp: IO[bytes], filename: str | bytes) -> None:
 
     extra = info.get("extra", b"")
 
+    xmp = info.get("xmp")
+    if xmp:
+        size = o16(31 + len(xmp))
+        extra += b"\xFF\xE1" + size + b"http://ns.adobe.com/xap/1.0/\x00" + xmp
+
     MAX_BYTES_IN_MARKER = 65533
     icc_profile = info.get("icc_profile")
     if icc_profile: