CSharpGL.Scene.ReadPixels C# (CSharp) Method

        private static unsafe List<Tuple<Point, uint>> ReadPixels(Rectangle target)
        {
            var result = new List<Tuple<Point, uint>>();

            // get coded color.
            using (var codedColor = new UnmanagedArray<Pixel>(target.Width * target.Height))
            {
                OpenGL.ReadPixels(target.X, target.Y, target.Width, target.Height,
                    OpenGL.GL_RGBA, OpenGL.GL_UNSIGNED_BYTE, codedColor.Header);

                var array = (Pixel*)codedColor.Header.ToPointer();
                int index = 0;
                var vertexIdList = new List<uint>();
                for (int yOffset = target.Height - 1; yOffset >= 0; yOffset--)
                {
                    for (int xOffset = 0; xOffset < target.Width; xOffset++)
                    {
                        Pixel pixel = array[index++];
                        // This is when (x, y) is not on background and some primitive is picked.
                        if (!pixel.IsWhite())
                        {
                            uint stageVertexId = pixel.ToStageVertexId();
                            if (!vertexIdList.Contains(stageVertexId))
                            {
                                result.Add(new Tuple<Point, uint>(
                                    new Point(target.X + xOffset, target.Y + yOffset), stageVertexId));
                                vertexIdList.Add(stageVertexId);
                            }
                        }
                    }
                }
            }

            return result;
        }