python: exposed CompressedImage and ImageView classes.

doc/python/magnum.rst

@@ -83,6 +83,23 @@
 
     See :ref:`Image2D` for more information.
 
+.. py:class:: magnum.CompressedImage1D
+
+    See :ref:`CompressedImage2D` for more information.
+
+.. py:class:: magnum.CompressedImage2D
+
+    An owning counterpart to :ref:`CompressedImageView2D` /
+    :ref:`MutableCompressedImageView2D`. Holds its own data buffer, thus
+    doesn't have an equivalent to :ref:`CompressedImageView2D.owner`. The
+    :ref:`data` view allows mutable access. Implicitly convertible to
+    :ref:`CompressedImageView2D` / :ref:`MutableCompressedImageView2D`, so all
+    APIs consuming image views work with this type as well.
+
+.. py:class:: magnum.CompressedImage3D
+
+    See :ref:`CompressedImage2D` for more information.
+
 .. py:class:: magnum.ImageView1D
 
     See :ref:`ImageView2D` for more information.
@@ -194,3 +211,88 @@
 
     This function is used to implement implicit conversion from
     :ref:`trade.ImageData3D` in the :ref:`trade` module.
+
+.. py:class:: magnum.CompressedImageView1D
+
+    See :ref:`CompressedImageView2D` for more information.
+
+.. py:class:: magnum.CompressedImageView2D
+
+    :TODO: remove this line once m.css stops ignoring first caption on a page
+
+    `Memory ownership and reference counting`_
+    ==========================================
+
+    Similarly to :ref:`corrade.containers.ArrayView` (and unlike in C++), the
+    view keeps a reference to the original memory owner object in the
+    :ref:`owner` field, meaning that calling :py:`del` on the original object
+    will *not* invalidate the view. Slicing a view creates a new view
+    referencing the same original object, without any dependency on the
+    previous view. That means a long chained slicing operation will not cause
+    increased memory usage.
+
+    The :ref:`owner` is :py:`None` if the view is empty.
+
+.. py:class:: magnum.CompressedImageView3D
+
+    See :ref:`CompressedImageView2D` for more information.
+
+.. py:class:: magnum.MutableCompressedImageView1D
+
+    See :ref:`CompressedImageView2D` for more information. The only difference
+    to the non-mutable variant is that it's possible to modify the image
+    through :ref:`data`.
+
+.. py:class:: magnum.MutableCompressedImageView2D
+
+    See :ref:`CompressedImageView2D` for more information. The only difference
+    to the non-mutable variant is that it's possible to modify the image
+    through :ref:`data`.
+
+.. py:class:: magnum.MutableImageView3D
+
+    See :ref:`CompressedImageView2D` for more information. The only difference
+    to the non-mutable variant is that it's possible to modify the image
+    through :ref:`data`.
+
+.. py:function:: magnum.CompressedImageView1D.__init__(self, arg0: magnum.CompressedImageView1D)
+    :raise RuntimeError: If :ref:`trade.ImageData1D.is_compressed` is
+        :py:`False`
+
+    This function is used to implement implicit conversion from
+    :ref:`trade.ImageData1D` in the :ref:`trade` module.
+
+.. py:function:: magnum.CompressedImageView2D.__init__(self, arg0: magnum.CompressedImageView2D)
+    :raise RuntimeError: If :ref:`trade.ImageData2D.is_compressed` is
+        :py:`False`
+
+    This function is used to implement implicit conversion from
+    :ref:`trade.ImageData2D` in the :ref:`trade` module.
+
+.. py:function:: magnum.CompressedImageView3D.__init__(self, arg0: magnum.CompressedImageView3D)
+    :raise RuntimeError: If :ref:`trade.ImageData3D.is_compressed` is
+        :py:`False`
+
+    This function is used to implement implicit conversion from
+    :ref:`trade.ImageData3D` in the :ref:`trade` module.
+
+.. py:function:: magnum.MutableCompressedImageView1D.__init__(self, arg0: magnum.MutableCompressedImageView1D)
+    :raise RuntimeError: If :ref:`trade.ImageData1D.is_compressed` is
+        :py:`False`
+
+    This function is used to implement implicit conversion from
+    :ref:`trade.ImageData1D` in the :ref:`trade` module.
+
+.. py:function:: magnum.MutableCompressedImageView2D.__init__(self, arg0: magnum.MutableCompressedImageView2D)
+    :raise RuntimeError: If :ref:`trade.ImageData2D.is_compressed` is
+        :py:`True`
+
+    This function is used to implement implicit conversion from
+    :ref:`trade.ImageData2D` in the :ref:`trade` module.
+
+.. py:function:: magnum.MutableCompressedImageView3D.__init__(self, arg0: magnum.MutableCompressedImageView3D)
+    :raise RuntimeError: If :ref:`trade.ImageData3D.is_compressed` is
+        :py:`False`
+
+    This function is used to implement implicit conversion from
+    :ref:`trade.ImageData3D` in the :ref:`trade` module.

doc/python/pages/changelog.rst

@@ -58,6 +58,8 @@ Changelog
 -   Exposed the :ref:`CompressedPixelFormat` enum, various pixel-format-related
     helper APIs are now properties on :ref:`PixelFormat` and
     :ref:`CompressedPixelFormat`
+-   Exposed :ref:`CompressedImage2D`, :ref:`CompressedImageView2D`,
+    :ref:`MutableCompressedImageView2D` and their 1D and 3D counterparts
 -   Exposed :ref:`Color3.from_xyz()`, :ref:`Color3.from_linear_rgb_int()`,
     :ref:`Color3.to_xyz()`, :ref:`Color3.to_linear_rgb_int()` and equivalent
     APIs on :ref:`Color4`

src/python/magnum/__init__.py

@@ -80,8 +80,11 @@ __all__ = [
     'PixelFormat', 'PixelStorage',
     'CompressedPixelFormat',
     'Image1D', 'Image2D', 'Image3D',
+    'CompressedImage1D', 'CompressedImage2D', 'CompressedImage3D',
     'ImageView1D', 'ImageView2D', 'ImageView3D',
     'MutableImageView1D', 'MutableImageView2D', 'MutableImageView3D',
+    'CompressedImageView1D', 'CompressedImageView2D', 'CompressedImageView3D',
+    'MutableCompressedImageView1D', 'MutableCompressedImageView2D', 'MutableCompressedImageView3D',
 
     'SamplerFilter', 'SamplerMipmap', 'SamplerWrapping',
 

src/python/magnum/magnum.cpp

@@ -170,6 +170,75 @@ template<class T> void imageViewFromMutable(py::class_<T, PyImageViewHolder<T>>&
         }), "Construct from a mutable view");
 }
 
+template<class T> void compressedImage(py::class_<T>& c) {
+    c
+        /* Constructors. Only the ones that are *not* taking an Array, as
+           Python has no way to "move" it in */
+        .def(py::init(), "Construct an image placeholder")
+
+        /* Properties */
+        .def_property_readonly("format", &T::format, "Format of compressed pixel data")
+        .def_property_readonly("size", [](T& self) {
+            return PyDimensionTraits<T::Dimensions, Int>::from(self.size());
+        }, "Image size")
+        .def_property_readonly("data", [](T& self) {
+            return Containers::pyArrayViewHolder(self.data(), self.data() ? py::cast(self) : py::none{});
+        }, "Raw image data");
+}
+
+template<class T> void compressedImageView(py::class_<T, PyImageViewHolder<T>>& c) {
+    /*
+        Missing APIs:
+
+        Type, ErasedType, Dimensions
+    */
+
+    py::implicitly_convertible<CompressedImage<T::Dimensions>, T>();
+
+    c
+        /* Constructors. The variants *not* taking an array view have to be
+           first, otherwise things fail on systems that don't have numpy
+           installed. See imageView() above for details */
+        .def(py::init([](CompressedPixelFormat format, const typename PyDimensionTraits<T::Dimensions, Int>::VectorType& size) {
+            return T{format, size};
+        }), "Construct an empty view")
+        .def(py::init([](CompressedPixelFormat format, const typename PyDimensionTraits<T::Dimensions, Int>::VectorType& size, const Containers::ArrayView<typename T::Type>& data) {
+            return pyImageViewHolder(T{format, size, data}, pyObjectHolderFor<Containers::PyArrayViewHolder>(data).owner);
+        }), "Constructor")
+        .def(py::init([](CompressedImage<T::Dimensions>& image) {
+            return pyImageViewHolder(T{image}, image.data() ? py::cast(image) : py::none{});
+        }), "Construct a view on an image")
+        .def(py::init([](const CompressedImageView<T::Dimensions, typename T::Type>& other) {
+            return pyImageViewHolder(CompressedImageView<T::Dimensions, typename T::Type>(other), pyObjectHolderFor<PyImageViewHolder>(other).owner);
+        }), "Construct from any type convertible to an image view")
+
+        /* Properties */
+        .def_property_readonly("format", &T::format, "Format of compressedpixel data")
+        .def_property_readonly("size", [](T& self) {
+            return PyDimensionTraits<T::Dimensions, Int>::from(self.size());
+        }, "Image size")
+        .def_property("data", [](T& self) {
+            return Containers::pyArrayViewHolder(self.data(), pyObjectHolderFor<PyImageViewHolder>(self).owner);
+        }, [](T& self, const Containers::ArrayView<typename T::Type>& data) {
+            self.setData(data);
+            pyObjectHolderFor<PyImageViewHolder>(self).owner =
+            pyObjectHolderFor<Containers::PyArrayViewHolder>(data).owner;
+        }, "Raw image data")
+
+        .def_property_readonly("owner", [](T& self) {
+            return pyObjectHolderFor<PyImageViewHolder>(self).owner;
+        }, "Memory owner");
+}
+
+template<class T> void compressedImageViewFromMutable(py::class_<T, PyImageViewHolder<T>>& c) {
+    py::implicitly_convertible<BasicMutableCompressedImageView<T::Dimensions>, T>();
+
+    c
+        .def(py::init([](const BasicMutableCompressedImageView<T::Dimensions>& other) {
+            return pyImageViewHolder(BasicCompressedImageView<T::Dimensions>(other), pyObjectHolderFor<PyImageViewHolder>(other).owner);
+        }), "Construct from a mutable view");
+}
+
 void magnum(py::module_& m) {
     m.attr("BUILD_DEPRECATED") =
         #ifdef MAGNUM_BUILD_DEPRECATED
@@ -540,6 +609,13 @@ void magnum(py::module_& m) {
     image(image2D);
     image(image3D);
 
+    py::class_<CompressedImage1D> compressedImage1D{m, "CompressedImage1D", "One-dimensional compressed image"};
+    py::class_<CompressedImage2D> compressedImage2D{m, "CompressedImage2D", "Two-dimensional compressed image"};
+    py::class_<CompressedImage3D> compressedImage3D{m, "CompressedImage3D", "Three-dimensional compressed image"};
+    compressedImage(compressedImage1D);
+    compressedImage(compressedImage2D);
+    compressedImage(compressedImage3D);
+
     py::class_<ImageView1D, PyImageViewHolder<ImageView1D>> imageView1D{m, "ImageView1D", "One-dimensional image view"};
     py::class_<ImageView2D, PyImageViewHolder<ImageView2D>> imageView2D{m, "ImageView2D", "Two-dimensional image view"};
     py::class_<ImageView3D, PyImageViewHolder<ImageView3D>> imageView3D{m, "ImageView3D", "Three-dimensional image view"};
@@ -558,6 +634,24 @@ void magnum(py::module_& m) {
     imageViewFromMutable(imageView2D);
     imageViewFromMutable(imageView3D);
 
+    py::class_<CompressedImageView1D, PyImageViewHolder<CompressedImageView1D>> compressedImageView1D{m, "CompressedImageView1D", "One-dimensional compressed image view"};
+    py::class_<CompressedImageView2D, PyImageViewHolder<CompressedImageView2D>> compressedImageView2D{m, "CompressedImageView2D", "Two-dimensional compressed image view"};
+    py::class_<CompressedImageView3D, PyImageViewHolder<CompressedImageView3D>> compressedImageView3D{m, "CompressedImageView3D", "Three-dimensional compressed image view"};
+    py::class_<MutableCompressedImageView1D, PyImageViewHolder<MutableCompressedImageView1D>> mutableCompressedImageView1D{m, "MutableCompressedImageView1D", "One-dimensional mutable compressed image view"};
+    py::class_<MutableCompressedImageView2D, PyImageViewHolder<MutableCompressedImageView2D>> mutableCompressedImageView2D{m, "MutableCompressedImageView2D", "Two-dimensional mutable compressed image view"};
+    py::class_<MutableCompressedImageView3D, PyImageViewHolder<MutableCompressedImageView3D>> mutableCompressedImageView3D{m, "MutableCompressedImageView3D", "Three-dimensional mutable compressed image view"};
+
+    compressedImageView(compressedImageView1D);
+    compressedImageView(compressedImageView2D);
+    compressedImageView(compressedImageView3D);
+    compressedImageView(mutableCompressedImageView1D);
+    compressedImageView(mutableCompressedImageView2D);
+    compressedImageView(mutableCompressedImageView3D);
+
+    compressedImageViewFromMutable(compressedImageView1D);
+    compressedImageViewFromMutable(compressedImageView2D);
+    compressedImageViewFromMutable(compressedImageView3D);
+
     py::enum_<SamplerFilter>{m, "SamplerFilter", "Texture sampler filtering"}
         .value("NEAREST", SamplerFilter::Nearest)
         .value("LINEAR", SamplerFilter::Linear);

src/python/magnum/test/test.py

@@ -183,6 +183,35 @@ class Image(unittest.TestCase):
         with self.assertRaisesRegex(NotImplementedError, "access to this pixel format is not implemented yet, sorry"):
             a.pixels
 
+class CompressedImage(unittest.TestCase):
+    def test_init_empty(self):
+        a = CompressedImage2D()
+        self.assertEqual(a.size, Vector2i())
+        self.assertEqual(a.format, CompressedPixelFormat(0))
+
+    @unittest.skip("No way to create a non-empty Image at the moment")
+    def test_data_access(self):
+        # Tested in test_gl_gl.Framebuffer.test_read_image instead
+        a = CompressedImage2D(CompressedPixelFormat.BC1_RGB_UNORM, Vector2i(3, 17)) # TODO
+        a_refcount = sys.getrefcount(a)
+
+        data = a.data
+        self.assertEqual(len(data), 3*17*1)
+        self.assertIs(data.owner, a)
+        self.assertEqual(sys.getrefcount(a), a_refcount + 1)
+
+        del data
+        self.assertEqual(sys.getrefcount(a), a_refcount)
+
+    def test_data_access_empty(self):
+        a = CompressedImage2D()
+        a_refcount = sys.getrefcount(a)
+
+        data = a.data
+        self.assertEqual(len(data), 0)
+        self.assertIs(data.owner, None)
+        self.assertEqual(sys.getrefcount(a), a_refcount)
+
 class ImageView(unittest.TestCase):
     def test_init(self):
         # 2x4 RGB pixels, padded for alignment
@@ -513,6 +542,140 @@ class ImageView(unittest.TestCase):
         with self.assertRaisesRegex(NotImplementedError, "access to this pixel format is not implemented yet, sorry"):
             a.pixels
 
+class CompressedImageView(unittest.TestCase):
+    def test_init(self):
+        # Four 64-bit blocks
+        data = (b'01234567'
+                b'89abcdef'
+                b'FEDCBA98'
+                b'76543210')
+        data_refcount = sys.getrefcount(data)
+
+        a = CompressedImageView2D(CompressedPixelFormat.BC1_RGB_UNORM, (4, 16), data)
+        self.assertEqual(a.size, Vector2i(4, 16))
+        self.assertEqual(a.format, CompressedPixelFormat.BC1_RGB_UNORM)
+        self.assertEqual(a.owner, data)
+        self.assertEqual(sys.getrefcount(data), data_refcount + 1)
+
+        del a
+        self.assertEqual(sys.getrefcount(data), data_refcount)
+
+    def test_init_empty(self):
+        a = MutableCompressedImageView1D(CompressedPixelFormat.ASTC_4X4_RGBA_UNORM, 32)
+        self.assertEqual(a.size, 32)
+        self.assertEqual(a.owner, None)
+
+    def test_init_mutable(self):
+        # Four 64-bit blocks
+        data = bytearray(b'01234567'
+                         b'89abcdef'
+                         b'FEDCBA98'
+                         b'76543210')
+        data_refcount = sys.getrefcount(data)
+
+        a = MutableCompressedImageView2D(CompressedPixelFormat.BC4_R_SNORM, (8, 8), data)
+        self.assertEqual(sys.getrefcount(data), data_refcount + 1)
+
+        # Back to immutable
+        b = CompressedImageView2D(a)
+        self.assertEqual(b.size, Vector2i(8, 8))
+        self.assertEqual(b.format, CompressedPixelFormat.BC4_R_SNORM)
+        self.assertEqual(len(b.data), 32)
+        self.assertIs(b.owner, data)
+        self.assertEqual(sys.getrefcount(data), data_refcount + 2)
+
+    @unittest.skip("No way to create a non-empty Image at the moment")
+    def test_init_image(self):
+        # TODO adapt from ImageView.test_init_image
+        pass
+
+    def test_init_image_empty(self):
+        a = CompressedImage2D()
+        a_refcount = sys.getrefcount(a)
+
+        view = CompressedImageView2D(a)
+        self.assertEqual(view.size, (0, 0))
+        self.assertIs(view.owner, None)
+        self.assertEqual(sys.getrefcount(a), a_refcount)
+
+        mview = MutableCompressedImageView2D(a)
+        self.assertEqual(mview.size, (0, 0))
+        self.assertIs(mview.owner, None)
+        self.assertEqual(sys.getrefcount(a), a_refcount)
+
+    def test_data_access(self):
+        # Two 128-bit blocks
+        data = (b'0123456789abcdef'
+                b'FEDCBA9876543210')
+        data_refcount = sys.getrefcount(data)
+
+        a = CompressedImageView2D(CompressedPixelFormat.BC7_RGBA_UNORM, (8, 4), data)
+        a_refcount = sys.getrefcount(a)
+        self.assertEqual(sys.getrefcount(data), data_refcount + 1)
+
+        a_data = a.data
+        self.assertEqual(len(a_data), 32)
+        self.assertEqual(a_data[9], '9')
+        self.assertEqual(a_data[20], 'B')
+        self.assertIs(a_data.owner, data)
+        # The data references the original data as an owner, not the view
+        self.assertEqual(sys.getrefcount(a), a_refcount)
+        self.assertEqual(sys.getrefcount(data), data_refcount + 2)
+
+        del a_data
+        self.assertEqual(sys.getrefcount(data), data_refcount + 1)
+
+    def test_mutable_data_access(self):
+        # Two 128-bit blocks
+        data = bytearray(b'0123456789abcdef'
+                         b'FEDCBA9876543210')
+        data_refcount = sys.getrefcount(data)
+
+        a = MutableCompressedImageView2D(CompressedPixelFormat.BC6H_RGB_SFLOAT, (4, 8), data)
+        a_refcount = sys.getrefcount(a)
+        self.assertEqual(sys.getrefcount(data), data_refcount + 1)
+
+        a_data = a.data
+        self.assertEqual(len(a_data), 32)
+        self.assertEqual(a_data[9], '9')
+        self.assertEqual(a_data[20], 'B')
+        self.assertIs(a_data.owner, data)
+        # The data references the original data as an owner, not the view
+        self.assertEqual(sys.getrefcount(a), a_refcount)
+        self.assertEqual(sys.getrefcount(data), data_refcount + 2)
+
+        a_data[9] = '_'
+        a_data[20] = '_'
+        self.assertEqual(data, b'012345678_abcdef'
+                               b'FEDC_A9876543210')
+
+        del a_data
+        self.assertEqual(sys.getrefcount(data), data_refcount + 1)
+
+    def test_set_data(self):
+        # Two 128-bit blocks
+        data = (b'0123456789ABCDEF'
+                b'fedcba9876543210')
+        data_refcount = sys.getrefcount(data)
+
+        a = CompressedImageView2D(CompressedPixelFormat.BC3_RGBA_SRGB, (4, 8), data)
+        self.assertIs(a.owner, data)
+        self.assertEqual(sys.getrefcount(data), data_refcount + 1)
+
+        data2 = (b'0123456789abcdef'
+                 b'FEDCBA9876543210')
+        data2_refcount = sys.getrefcount(data2)
+
+        # Replacing the data should disown the original object and point to the
+        # new one
+        a.data = data2
+        self.assertEqual(bytes(a.data),
+            b'0123456789abcdef'
+            b'FEDCBA9876543210')
+        self.assertIs(a.owner, data2)
+        self.assertEqual(sys.getrefcount(data), data_refcount)
+        self.assertEqual(sys.getrefcount(data2), data2_refcount + 1)
+
 class UtilityCopy(unittest.TestCase):
     def test_1d(self):
         a_data = array.array('f', [1.0, 2.0, 3.0, 4.0, 5.0, 6.0])

src/python/magnum/test/test_trade.py

@@ -81,14 +81,20 @@ class ImageData(unittest.TestCase):
         view = ImageView2D(image)
         mutable_view = MutableImageView2D(image)
 
+        with self.assertRaisesRegex(RuntimeError, "image is not compressed"):
+            CompressedImageView2D(image)
+        with self.assertRaisesRegex(RuntimeError, "image is not compressed"):
+            MutableCompressedImageView2D(image)
+
     def test_convert_view_compressed(self):
         # The only way to get an image instance is through a manager
         importer = trade.ImporterManager().load_and_instantiate('DdsImporter')
         importer.open_file(os.path.join(os.path.dirname(__file__), "rgba_dxt1.dds"))
         image = importer.image2d(0)
 
-        # No compressed-image-related APIs exposed ATM, so just verifying the
-        # uncompressed ones fail properly
+        view = CompressedImageView2D(image)
+        mutable_view = MutableCompressedImageView2D(image)
+
         with self.assertRaisesRegex(RuntimeError, "image is compressed"):
             view = ImageView2D(image)
         with self.assertRaisesRegex(RuntimeError, "image is compressed"):

src/python/magnum/trade.cpp

@@ -177,6 +177,22 @@ template<UnsignedInt dimensions, class T> PyObject* implicitlyConvertibleToImage
     return r;
 }
 
+template<UnsignedInt dimensions, class T> PyObject* implicitlyConvertibleToCompressedImageView(PyObject* obj, PyTypeObject*) {
+    py::detail::make_caster<Trade::ImageData<dimensions>> caster;
+    if(!caster.load(obj, false)) {
+        return nullptr;
+    }
+
+    Trade::ImageData<dimensions>& data = caster;
+    if(!data.isCompressed()) {
+        PyErr_SetString(PyExc_RuntimeError, "image is not compressed");
+        throw py::error_already_set{};
+    }
+
+    auto r = pyCastButNotShitty(pyImageViewHolder(CompressedImageView<dimensions, T>(data), py::reinterpret_borrow<py::object>(obj))).release().ptr();
+    return r;
+}
+
 template<UnsignedInt dimensions, class T> Containers::PyArrayViewHolder<Containers::PyStridedArrayView<dimensions, T>> imagePixelsView(Trade::ImageData<dimensions>& image, const Containers::ArrayView<T> data, const Containers::StridedArrayView<dimensions + 1, T>& pixels) {
     const PixelFormat format = image.format();
     const std::size_t itemsize = pixelFormatSize(format);
@@ -218,6 +234,14 @@ template<UnsignedInt dimensions> void imageData(py::class_<Trade::ImageData<dime
         auto tinfo = py::detail::get_type_info(typeid(ImageView<dimensions, const char>));
         CORRADE_INTERNAL_ASSERT(tinfo);
         tinfo->implicit_conversions.push_back(implicitlyConvertibleToImageView<dimensions, const char>);
+    } {
+        auto tinfo = py::detail::get_type_info(typeid(CompressedImageView<dimensions, char>));
+        CORRADE_INTERNAL_ASSERT(tinfo);
+        tinfo->implicit_conversions.push_back(implicitlyConvertibleToCompressedImageView<dimensions, char>);
+    } {
+        auto tinfo = py::detail::get_type_info(typeid(CompressedImageView<dimensions, const char>));
+        CORRADE_INTERNAL_ASSERT(tinfo);
+        tinfo->implicit_conversions.push_back(implicitlyConvertibleToCompressedImageView<dimensions, const char>);
     }
 
     c