add jpeg quality option

docs/source/preparing_datasets/basic_dataset_conversion.md

@@ -43,7 +43,7 @@ out = ('/local/data', 'oci://bucket/data')
 | Numerical String   | 'str_float'   | `StrFloat`   | stores in UTF-8          |
 | Numerical String   | 'str_decimal' | `StrDecimal` | stores in UTF-8          |
 | Image              | 'pil'         | `PIL`        | raw PIL image class ([link]((https://pillow.readthedocs.io/en/stable/reference/Image.html)))            |
-| Image              | 'jpeg'        | `JPEG`       | PIL image as JPEG        |
+| Image              | 'jpeg:quality'        | `JPEG`       | PIL image as JPEG, quality between 0 and 100        |
 | Image              | 'png'         | `PNG`        | PIL image as PNG         |
 | Pickle             | 'pkl'         | `Pickle`     | arbitrary Python objects |
 | JSON               | 'json'        | `JSON`       | arbitrary data as JSON   |
@@ -52,7 +52,7 @@ Here's an example where the field `x` is an image, and `y` is a class label, as
 <!--pytest.mark.skip-->
 ```python
 column = {
-    'x': 'jpeg',
+    'x': 'jpeg:90',
     'y': 'int8',
 }
 ```

streaming/base/format/mds/encodings.py

@@ -464,7 +464,29 @@ def decode(self, data: bytes) -> Image.Image:
 
 
 class JPEG(Encoding):
-    """Store PIL image as JPEG."""
+    """Store PIL image as JPEG. Optionally specify quality."""
+
+    def __init__(self, quality: int = 75):
+        if not isinstance(quality, int):
+            raise ValueError('JPEG quality must be an integer')
+        if not (0 <= quality <= 100):
+            raise ValueError('JPEG quality must be between 0 and 100')
+        self.quality = quality
+
+    @classmethod
+    def from_str(cls, config: str) -> Self:
+        """Parse this encoding from string.
+
+        Args:
+            text (str): The string to parse.
+
+        Returns:
+            Self: The initialized Encoding.
+        """
+        if config == '':
+            return cls()
+        else:
+            return cls(int(config))
 
     def encode(self, obj: Image.Image) -> bytes:
         self._validate(obj, Image.Image)
@@ -474,7 +496,7 @@ def encode(self, obj: Image.Image) -> bytes:
                 return f.read()
         else:
             out = BytesIO()
-            obj.save(out, format='JPEG')
+            obj.save(out, format='JPEG', quality=self.quality)
             return out.getvalue()
 
     def decode(self, data: bytes) -> Image.Image:

tests/test_encodings.py

@@ -194,6 +194,30 @@ def test_jpeg_encode_decode(self, mode: str):
         dec_data = dec_data.convert('I')
         assert isinstance(dec_data, Image.Image)
 
+    @pytest.mark.parametrize('mode', ['L', 'RGB'])
+    def test_jpeg_encode_decode_with_quality(self, mode: str):
+        jpeg_enc = mdsEnc.JPEG(quality=50)
+        assert jpeg_enc.size is None
+
+        # Creating the (32 x 32) NumPy Array with random values
+        np_data = np.random.randint(255, size=(32, 32), dtype=np.uint32)
+        # Default image mode of PIL Image is 'I'
+        img = Image.fromarray(np_data).convert(mode)
+
+        # Test encode
+        enc_data = jpeg_enc.encode(img)
+        assert isinstance(enc_data, bytes)
+
+        # Test decode
+        dec_data = jpeg_enc.decode(enc_data)
+        dec_data = dec_data.convert('I')
+        assert isinstance(dec_data, Image.Image)
+
+    @pytest.mark.parametrize('quality', [-1, 101, 'foo'])
+    def test_jpeg_encode_decode_with_quality_invalid(self, quality: Any):
+        with pytest.raises(ValueError):
+            mdsEnc.JPEG(quality=quality)
+
     @pytest.mark.parametrize('mode', ['L', 'RGB'])
     def test_jpegfile_encode_decode(self, mode: str):
         jpeg_enc = mdsEnc.JPEG()
@@ -224,6 +248,7 @@ def test_jpeg_encode_invalid_data(self, data: Any):
         with pytest.raises(AttributeError):
             jpeg_enc = mdsEnc.JPEG()
             _ = jpeg_enc.encode(data)
+
 
     @pytest.mark.parametrize('mode', ['I', 'L', 'RGB'])
     def test_png_encode_decode(self, mode: str):