ENH: add decode_as_image() to ContentStreams

closes py-pdf#2613

Author: pubpub-zz

pypdf/generic/_data_structures.py

@@ -947,6 +947,26 @@ def flate_encode(self, level: int = -1) -> "EncodedStreamObject":
         retval._data = FlateDecode.encode(b_(self._data), level)
         return retval
 
+    def decode_as_image(self) -> Any:
+        """
+        Try to decode the stream object as an image
+
+        Returns:
+            a PIL image if proper decoding has been found
+        """
+        from ..filters import _xobj_to_image
+
+        if self.get("/Subtype", "") != "/Image":
+            try:
+                msg = f"{self.indirect_reference} does not seems to be an Image"  # pragma: no cover
+            except AttributeError:
+                msg = f"{self.__repr__()} object does not seems to be an Image"  # pragma: no cover
+            logger_warning(msg, __name__)
+        extension, byte_stream, img = _xobj_to_image(self)
+        if extension is None:
+            return None  # pragma: no cover
+        return img
+
 
 class DecodedStreamObject(StreamObject):
     pass

tests/test_images.py

@@ -346,3 +346,24 @@ def test_corrupted_jpeg_iss2266(pdf, pdf_name, images, images_name, filtr):
             print(fn)  # noqa: T201
             img = Image.open(BytesIO(zf.read(fn)))
             assert image_similarity(reader.pages[p].images[i].image, img) >= 0.99
+
+
+@pytest.mark.enable_socket()
+def test_extract_image_from_object(caplog):
+    url = "https://github.com/py-pdf/pypdf/files/15176076/B2.pdf"
+    name = "iss2613.pdf"
+    reader = PdfReader(BytesIO(get_data_from_url(url, name=name)))
+    image = reader.pages[0]["/Resources"]["/Pattern"]["/P1"]["/Resources"]["/XObject"][
+        "/X1"
+    ].decode_as_image()
+    assert isinstance(image, Image.Image)
+    with pytest.raises(Exception):
+        co = reader.pages[0].get_contents()
+        co.decode_as_image()
+    assert "does not seems to be an Image" in caplog.text
+    caplog.clear()
+    co.indirect_reference = "for_test"
+    with pytest.raises(Exception):
+        co = reader.pages[0].get_contents()
+        co.decode_as_image()
+    assert "does not seems to be an Image" in caplog.text