python: bind framebuffer reading.

src/python/magnum/CMakeLists.txt

@@ -74,7 +74,9 @@ set(magnum_trade_SRCS
 if(NOT MAGNUM_BUILD_STATIC)
     if(Magnum_GL_FOUND)
         pybind11_add_module(magnum_gl SYSTEM ${magnum_gl_SRCS})
-        target_include_directories(magnum_gl PRIVATE ${PROJECT_SOURCE_DIR}/src/python)
+        target_include_directories(magnum_gl PRIVATE
+            ${PROJECT_SOURCE_DIR}/src
+            ${PROJECT_SOURCE_DIR}/src/python)
         target_link_libraries(magnum_gl PRIVATE Magnum::GL)
         set_target_properties(magnum_gl PROPERTIES
             FOLDER "python"

src/python/magnum/gl.cpp

@@ -27,6 +27,7 @@
 #include <pybind11/stl.h> /* for Mesh.buffers */
 #include <Corrade/Containers/ArrayView.h>
 #include <Corrade/Utility/FormatStl.h>
+#include <Magnum/ImageView.h>
 #include <Magnum/GL/AbstractShaderProgram.h>
 #include <Magnum/GL/Attribute.h>
 #include <Magnum/GL/Buffer.h>
@@ -38,6 +39,8 @@
 #include <Magnum/GL/RenderbufferFormat.h>
 #include <Magnum/Math/Color.h>
 
+#include "Magnum/Python.h"
+
 #include "corrade/PyArrayView.h"
 #include "corrade/EnumOperators.h"
 #include "magnum/bootstrap.h"
@@ -295,7 +298,10 @@ void gl(py::module& m) {
         /* Using lambdas to avoid method chaining getting into signatures */
         .def("clear", [](GL::AbstractFramebuffer& self, GL::FramebufferClear mask) {
             self.clear(mask);
-        });
+        }, "Clear specified buffers in the framebuffer")
+        .def("read", [](GL::AbstractFramebuffer& self, const Range2Di& rectangle, PyImageView<2, char>& image) {
+            self.read(rectangle, image);
+        }, "Read block of pixels from the framebuffer to an image view");
 
     NonDestructibleBase<GL::DefaultFramebuffer, GL::AbstractFramebuffer> defaultFramebuffer{m,
         "DefaultFramebuffer", "Default framebuffer"};

src/python/magnum/test/test_gl_gl.py

@@ -74,6 +74,23 @@ class Framebuffer(GLTestCase):
         self.assertIs(framebuffer.attached[0], renderbuffer)
         self.assertEqual(sys.getrefcount(renderbuffer), renderbuffer_refcount + 1)
 
+    def test_read(self):
+        renderbuffer = gl.Renderbuffer()
+        renderbuffer.set_storage(gl.RenderbufferFormat.RGBA8, (4, 4))
+
+        framebuffer = gl.Framebuffer(((0, 0), (4, 4)))
+        framebuffer.attach_renderbuffer(gl.Framebuffer.ColorAttachment(0), renderbuffer)
+
+        gl.Renderer.clear_color = Color4(1.0, 0.5, 0.75)
+        framebuffer.clear(gl.FramebufferClear.COLOR)
+
+        a = MutableImageView2D(PixelFormat.RGBA8UNORM, (2, 2), bytearray(16))
+        framebuffer.read(Range2Di.from_size((1, 1), (2, 2)), a)
+        self.assertEqual(a.size, Vector2i(2, 2))
+        self.assertEqual(ord(a.pixels[0, 0, 0]), 0xff)
+        self.assertEqual(ord(a.pixels[0, 1, 1]), 0x80)
+        self.assertEqual(ord(a.pixels[1, 0, 2]), 0xbf)
+
 class Mesh(GLTestCase):
     def test_init(self):
         a = gl.Mesh()