Added PyEncoder

Tests/test_imagefile.py

@@ -196,6 +196,11 @@ def decode(self, buffer):
         return -1, 0
 
 
+class MockPyEncoder(ImageFile.PyEncoder):
+    def encode(self, buffer):
+        return 1, 1, b""
+
+
 xoff, yoff, xsize, ysize = 10, 20, 100, 100
 
 
@@ -207,53 +212,58 @@ def _open(self):
         self.tile = [("MOCK", (xoff, yoff, xoff + xsize, yoff + ysize), 32, None)]
 
 
-class TestPyDecoder:
-    def get_decoder(self):
-        decoder = MockPyDecoder(None)
+class CodecsTest:
+    @classmethod
+    def setup_class(cls):
+        cls.decoder = MockPyDecoder(None)
+        cls.encoder = MockPyEncoder(None)
+
+        def decoder_closure(mode, *args):
+            cls.decoder.__init__(mode, *args)
+            return cls.decoder
 
-        def closure(mode, *args):
-            decoder.__init__(mode, *args)
-            return decoder
+        def encoder_closure(mode, *args):
+            cls.encoder.__init__(mode, *args)
+            return cls.encoder
 
-        Image.register_decoder("MOCK", closure)
-        return decoder
+        Image.register_decoder("MOCK", decoder_closure)
+        Image.register_encoder("MOCK", encoder_closure)
 
+
+class TestPyDecoder(CodecsTest):
     def test_setimage(self):
         buf = BytesIO(b"\x00" * 255)
 
         im = MockImageFile(buf)
-        d = self.get_decoder()
 
         im.load()
 
-        assert d.state.xoff == xoff
-        assert d.state.yoff == yoff
-        assert d.state.xsize == xsize
-        assert d.state.ysize == ysize
+        assert self.decoder.state.xoff == xoff
+        assert self.decoder.state.yoff == yoff
+        assert self.decoder.state.xsize == xsize
+        assert self.decoder.state.ysize == ysize
 
         with pytest.raises(ValueError):
-            d.set_as_raw(b"\x00")
+            self.decoder.set_as_raw(b"\x00")
 
     def test_extents_none(self):
         buf = BytesIO(b"\x00" * 255)
 
         im = MockImageFile(buf)
         im.tile = [("MOCK", None, 32, None)]
-        d = self.get_decoder()
 
         im.load()
 
-        assert d.state.xoff == 0
-        assert d.state.yoff == 0
-        assert d.state.xsize == 200
-        assert d.state.ysize == 200
+        assert self.decoder.state.xoff == 0
+        assert self.decoder.state.yoff == 0
+        assert self.decoder.state.xsize == 200
+        assert self.decoder.state.ysize == 200
 
     def test_negsize(self):
         buf = BytesIO(b"\x00" * 255)
 
         im = MockImageFile(buf)
         im.tile = [("MOCK", (xoff, yoff, -10, yoff + ysize), 32, None)]
-        self.get_decoder()
 
         with pytest.raises(ValueError):
             im.load()
@@ -267,11 +277,98 @@ def test_oversize(self):
 
         im = MockImageFile(buf)
         im.tile = [("MOCK", (xoff, yoff, xoff + xsize + 100, yoff + ysize), 32, None)]
-        self.get_decoder()
 
         with pytest.raises(ValueError):
             im.load()
 
         im.tile = [("MOCK", (xoff, yoff, xoff + xsize, yoff + ysize + 100), 32, None)]
         with pytest.raises(ValueError):
             im.load()
+
+    def test_decode(self):
+        decoder = ImageFile.PyDecoder(None)
+        with pytest.raises(NotImplementedError):
+            decoder.decode(None)
+
+
+class TestPyEncoder(CodecsTest):
+    def test_setimage(self):
+        buf = BytesIO(b"\x00" * 255)
+
+        im = MockImageFile(buf)
+
+        fp = BytesIO()
+        ImageFile._save(
+            im, fp, [("MOCK", (xoff, yoff, xoff + xsize, yoff + ysize), 0, "RGB")]
+        )
+
+        assert self.encoder.state.xoff == xoff
+        assert self.encoder.state.yoff == yoff
+        assert self.encoder.state.xsize == xsize
+        assert self.encoder.state.ysize == ysize
+
+    def test_extents_none(self):
+        buf = BytesIO(b"\x00" * 255)
+
+        im = MockImageFile(buf)
+        im.tile = [("MOCK", None, 32, None)]
+
+        fp = BytesIO()
+        ImageFile._save(im, fp, [("MOCK", None, 0, "RGB")])
+
+        assert self.encoder.state.xoff == 0
+        assert self.encoder.state.yoff == 0
+        assert self.encoder.state.xsize == 200
+        assert self.encoder.state.ysize == 200
+
+    def test_negsize(self):
+        buf = BytesIO(b"\x00" * 255)
+
+        im = MockImageFile(buf)
+
+        fp = BytesIO()
+        with pytest.raises(ValueError):
+            ImageFile._save(
+                im, fp, [("MOCK", (xoff, yoff, -10, yoff + ysize), 0, "RGB")]
+            )
+
+        with pytest.raises(ValueError):
+            ImageFile._save(
+                im, fp, [("MOCK", (xoff, yoff, xoff + xsize, -10), 0, "RGB")]
+            )
+
+    def test_oversize(self):
+        buf = BytesIO(b"\x00" * 255)
+
+        im = MockImageFile(buf)
+
+        fp = BytesIO()
+        with pytest.raises(ValueError):
+            ImageFile._save(
+                im,
+                fp,
+                [("MOCK", (xoff, yoff, xoff + xsize + 100, yoff + ysize), 0, "RGB")],
+            )
+
+        with pytest.raises(ValueError):
+            ImageFile._save(
+                im,
+                fp,
+                [("MOCK", (xoff, yoff, xoff + xsize, yoff + ysize + 100), 0, "RGB")],
+            )
+
+    def test_encode(self):
+        encoder = ImageFile.PyEncoder(None)
+        with pytest.raises(NotImplementedError):
+            encoder.encode(None)
+
+        bytes_consumed, errcode = encoder.encode_to_pyfd()
+        assert bytes_consumed == 0
+        assert ImageFile.ERRORS[errcode] == "bad configuration"
+
+        encoder._pushes_fd = True
+        with pytest.raises(NotImplementedError):
+            encoder.encode_to_pyfd()
+
+        with pytest.raises(NotImplementedError):
+            encoder.encode_to_file(None, None)

docs/handbook/appendices.rst

@@ -8,4 +8,4 @@ Appendices
 
   image-file-formats
   text-anchors
-  writing-your-own-file-decoder
+  writing-your-own-image-plugin

docs/handbook/writing-your-own-file-decoder.rst → docs/handbook/writing-your-own-image-plugin.rst

@@ -4,10 +4,9 @@ Writing Your Own Image Plugin
 =============================
 
 Pillow uses a plugin model which allows you to add your own
-decoders to the library, without any changes to the library
-itself. Such plugins usually have names like
-:file:`XxxImagePlugin.py`, where ``Xxx`` is a unique format name
-(usually an abbreviation).
+decoders and encoders to the library, without any changes to the library
+itself. Such plugins usually have names like :file:`XxxImagePlugin.py`,
+where ``Xxx`` is a unique format name (usually an abbreviation).
 
 .. warning:: Pillow >= 2.1.0 no longer automatically imports any file
              in the Python path with a name ending in
@@ -413,23 +412,24 @@ value, or if there is a read error from the file. This function should
 free any allocated memory and release any resources from external
 libraries.
 
-.. _file-decoders-py:
+.. _file-codecs-py:
 
-Writing Your Own File Decoder in Python
-=======================================
+Writing Your Own File Codec in Python
+=====================================
 
-Python file decoders should derive from
-:py:class:`PIL.ImageFile.PyDecoder` and should at least override the
-decode method. File decoders should be registered using
-:py:meth:`PIL.Image.register_decoder`. As in the C implementation of
-the file decoders, there are three stages in the lifetime of a
-Python-based file decoder:
+Python file decoders and encoders should derive from
+:py:class:`PIL.ImageFile.PyDecoder` and :py:class:`PIL.ImageFile.PyEncoder`
+respectively, and should at least override the decode or encode method.
+They should be registered using :py:meth:`PIL.Image.register_decoder` and
+:py:meth:`PIL.Image.register_encoder`. As in the C implementation of
+the file codecs, there are three stages in the lifetime of a
+Python-based file codec:
 
 1. Setup: Pillow looks for the decoder in the registry, then
    instantiates the class.
 
-2. Decoding: The decoder instance's ``decode`` method is repeatedly
-   called with a buffer of data to be interpreted.
-
-3. Cleanup: The decoder instance's ``cleanup`` method is called.
+2. Transforming: The instance's ``decode`` method is repeatedly called with
+   a buffer of data to be interpreted, or the ``encode`` method is repeatedly
+   called with the size of data to be output.
 
+3. Cleanup: The instance's ``cleanup`` method is called.

docs/reference/ImageFile.rst

@@ -40,8 +40,16 @@ Classes
 .. autoclass:: PIL.ImageFile.Parser()
     :members:
 
+.. autoclass:: PIL.ImageFile.PyCodec()
+    :members:
+
 .. autoclass:: PIL.ImageFile.PyDecoder()
     :members:
+    :show-inheritance:
+
+.. autoclass:: PIL.ImageFile.PyEncoder()
+    :members:
+    :show-inheritance:
 
 .. autoclass:: PIL.ImageFile.ImageFile()
     :member-order: bysource