2d Texture Resizing

[maptz]

Hi,

I've got an app that shows video frames in a Silk.Net window. Each video frame is drawn as a texture as per the Silk.Net examples.

What I can't for the life of me work out is how to get the texture to fill the screen as I resize the window?

Can anyone give me some pointers?

public class RotatingDiscDisplay : OpenGLVideoDisplay
{
	public float _angle = 0.0f;

	private string EmptyImagePath = "silk.png";

	protected override void OnUpdatingTexture()
	{
		base.OnUpdatingTexture();

		_angle += 1;

		using var image = Image.Load<Bgra32>(EmptyImagePath);
		var newWidth = image.Width * 2;
		var newHeight = image.Height * 2;
		image.Mutate(x => x.Resize(image.Width * 2, image.Height * 2).Rotate(_angle));

		//IPath yourPolygon = new Star(x: 100.0f, y: 100.0f, prongs: 5, innerRadii: 20.0f, outerRadii: 30.0f);

		//image.Mutate(x => x.Fill(Color.Red, yourPolygon)); // fill the star with red

		DrawingOptions options = new()
		{
			GraphicsOptions = new()
			{
				ColorBlendingMode = PixelColorBlendingMode.Multiply
			}
		};

		IBrush brush = Brushes.Horizontal(Color.Red, Color.Blue);
		IPen pen = Pens.DashDot(Color.Green, 5);
		IPath yourPolygon = new Star(x: 100.0f, y: 100.0f, prongs: 5, innerRadii: 20.0f, outerRadii: 30.0f);
		image.Mutate(x => x.Fill(options, brush, yourPolygon)
						   .Draw(options, pen, yourPolygon));

		var yourPolygon2 = new SixLabors.ImageSharp.Rectangle(0, 0, 100, 100);
		image.Mutate(x => x.Fill(options, brush, yourPolygon)
						   .Draw(options, pen, yourPolygon));

		// Draws a star with horizontal red and blue hatching with a dash dot pattern outline.
		image.Mutate(x => x.Fill(Color.Green, yourPolygon2));

	https://stackoverflow.com/questions/50025908/convert-imagergba32-to-byte-using-imagesharp
		var _IMemoryGroup = image.GetPixelMemoryGroup();
		var _MemoryGroup = _IMemoryGroup.ToArray()[0];
		var PixelData = MemoryMarshal.AsBytes(_MemoryGroup.Span).ToArray();
		Texture.Update(PixelData, (uint)image.Width, (uint)image.Height);

		//Look at how you could manipulate pixels
		//https://docs.sixlabors.com/articles/imagesharp/pixelbuffers.html
		//https://github.com/SixLabors/Samples/blob/main/ImageSharp/DrawWaterMarkOnImage/Program.cs


		//Appears you can overlay images
		//image1.Mutate(i => i.Resize(800, 600, KnownResamplers.Lanczos3));
		//image.Mutate(i => i.Resize(1150, 600, KnownResamplers.Lanczos3).BokehBlur().DrawImage(image1, new Point(180, 0), opacity: 1f).Brightness(1.0f));

	}

	protected override void OnInitializingTexture()
	{
		base.OnInitializingTexture();

		//newTexture = new Texture(Gl, EmptyImagePath);
		//OR

		//We need it ot be 32 bit ARGB
		//https://docs.sixlabors.com/
		//using var image = Image.Load<Argb32>(EmptyImagePath);
		using var image = Image.Load<Bgra32>(EmptyImagePath);
		var newWidth = image.Width * 2;
		var newHeight = image.Height * 2;
		image.Mutate(x => x.Resize(image.Width * 2, image.Height * 2).Rotate(20));


	https://stackoverflow.com/questions/50025908/convert-imagergba32-to-byte-using-imagesharp
		var _IMemoryGroup = image.GetPixelMemoryGroup();
		var _MemoryGroup = _IMemoryGroup.ToArray()[0];
		var PixelData = MemoryMarshal.AsBytes(_MemoryGroup.Span).ToArray();
		var newTexture = new Texture(GL, PixelData, (uint)image.Width, (uint)image.Height);
		if (Texture != newTexture)
		{
			var oldTexture = Texture;
			Texture = newTexture;
			if (oldTexture != null)
				oldTexture.Dispose();
		}
	}
}


public class OpenGLVideoDisplay
{
	private IWindow _window;
	private GL _gl;
	protected GL GL { get => _gl; }

	private BufferObject<float> _vbo;
	private BufferObject<uint> _ebo;
	private VertexArrayObject<float, uint> _vao;
	//Create a texture object.
	private Texture _texture;
	private Shader _shader;

	protected IWindow Window { get => _window; }
	protected Texture Texture
	{
		get => _texture; 
		set
		{
			_texture = value;
		}
	}

	// OpenGL has image origin in the bottom-left corner.
	private readonly float[] Vertices =
	{
            //X    Y      Z     U   V
             1.0f,  1.0f, 0.0f, 1f, 0f,
			 1.0f, -1.0f, 0.0f, 1f, 1f,
			-1.0f, -1.0f, 0.0f, 0f, 1f,
			-1.0f,  1.0f, 1.0f, 0f, 0f
		};

	private readonly uint[] Indices =
	{
			0, 1, 3,
			1, 2, 3
		};


	public void Start()
	{
		var options = WindowOptions.Default;
		options.Size = new Vector2D<int>(1920, 1080);
		options.Title = "";
		options.WindowBorder = WindowBorder.Fixed;
		_window = global::Silk.NET.Windowing.Window.Create(options);

		_window.Load += OnLoad;
		_window.Render += OnRender;
		_window.Resize += _window_Resize;
		_window.Closing += OnClose;

		_window.Run();
	}

	private void _window_Resize(Vector2D<int> obj)
	{
		
	}

	private unsafe void OnLoad()
	{
		IInputContext input = _window.CreateInput();
		for (int i = 0; i < input.Keyboards.Count; i++)
		{
			input.Keyboards[i].KeyDown += KeyDown;
		}

		_gl = GL.GetApi(_window);

		_ebo = new BufferObject<uint>(_gl, Indices, BufferTargetARB.ElementArrayBuffer);
		_vbo = new BufferObject<float>(_gl, Vertices, BufferTargetARB.ArrayBuffer);
		_vao = new VertexArrayObject<float, uint>(_gl, _vbo, _ebo);

		_vao.VertexAttributePointer(0, 3, VertexAttribPointerType.Float, 5, 0);
		_vao.VertexAttributePointer(1, 2, VertexAttribPointerType.Float, 5, 3);

		_shader = new Shader(_gl, "shader.vert", "shader.frag");

		InitializeTexture();
		_hasLoaded = true;
	}



	protected virtual void OnUpdatingTexture()
	{

	}
	private void UpdateTexture()
	{
		OnUpdatingTexture();
	}

	private void InitializeTexture()
	{
		OnInitializingTexture();

	}

	protected virtual void OnInitializingTexture()
	{
	}


	private bool _hasLoaded;
	private long _lastRender = 0;

	public List<double> _lastFramesMs = new List<double>();

	private unsafe void OnRender(double obj)
	{
		var now = DateTime.Now.Ticks;
		var ticks = now - _lastRender;
		var ticksPerSeconds = 10_000_000;
		_lastRender = now;
		var msSinceLast = 1000.0 * ticks / (double)ticksPerSeconds;
		_lastFramesMs.Add(msSinceLast);
		if (_lastFramesMs.Count == 50)
		{
			var avgMSPerFrame = _lastFramesMs.Average();
			Console.WriteLine("Avg frame gap: " + msSinceLast);
			var fps = 1.0 / (avgMSPerFrame / 1000.0);
			Console.WriteLine("Avg fps: " + fps);
			_lastFramesMs.Clear();
		}

		UpdateTexture();

		_gl.Clear((uint)ClearBufferMask.ColorBufferBit);

		_vao.Bind();
		_shader.Use();
		//Bind a texture and and set the uTexture0 to use texture0.
		_texture.Bind(TextureUnit.Texture0);
		_shader.SetUniform("uTexture0", 0);

		_gl.DrawElements(PrimitiveType.Triangles, (uint)Indices.Length, DrawElementsType.UnsignedInt, null);
	}

	private void OnClose()
	{
		OnClosing();
		_vbo.Dispose();
		_ebo.Dispose();
		_vao.Dispose();
		_shader.Dispose();
		//Remember to dispose the texture.
		_texture.Dispose();
	}

	protected virtual void OnClosing()
	{
		
	}

	protected virtual void OnKeyDown(Key key)
	{
		if (key == Key.Escape)
		{
			_window.Close();
		}
	}

	private void KeyDown(IKeyboard arg1, Key arg2, int arg3)
	{
		OnKeyDown(arg2);
	}
}

public class Texture : IDisposable
{
	private uint _handle;
	private GL _gl;

	public unsafe Texture(GL gl, Image<Rgba32> img)
	{
		_gl = gl;

		_handle = _gl.GenTexture();
		Bind();

		//Reserve enough memory from the gpu for the whole image
		gl.TexImage2D(TextureTarget.Texture2D, 0, InternalFormat.Rgba8, (uint)img.Width, (uint)img.Height, 0, PixelFormat.Rgba, PixelType.UnsignedByte, null);

		img.ProcessPixelRows(accessor =>
		{
			//ImageSharp 2 does not store images in contiguous memory by default, so we must send the image row by row
			for (int y = 0; y < accessor.Height; y++)
			{
				fixed (void* data = accessor.GetRowSpan(y))
				{
					//Loading the actual image.
					gl.TexSubImage2D(TextureTarget.Texture2D, 0, 0, y, (uint)accessor.Width, 1, PixelFormat.Rgba, PixelType.UnsignedByte, data);
				}
			}
		});

		SetParameters();

	}


	public unsafe Texture(GL gl, string path)
	{
		_gl = gl;

		_handle = _gl.GenTexture();
		Bind();

		//Loading an image using imagesharp.
		using (var img = Image.Load<Rgba32>(path))
		{
			//Reserve enough memory from the gpu for the whole image
			gl.TexImage2D(TextureTarget.Texture2D, 0, InternalFormat.Rgba8, (uint)img.Width, (uint)img.Height, 0, PixelFormat.Rgba, PixelType.UnsignedByte, null);

			img.ProcessPixelRows(accessor =>
			{
				//ImageSharp 2 does not store images in contiguous memory by default, so we must send the image row by row
				for (int y = 0; y < accessor.Height; y++)
				{
					fixed (void* data = accessor.GetRowSpan(y))
					{
						//Loading the actual image.
						gl.TexSubImage2D(TextureTarget.Texture2D, 0, 0, y, (uint)accessor.Width, 1, PixelFormat.Rgba, PixelType.UnsignedByte, data);
					}
				}
			});
		}

		SetParameters();

	}

	public unsafe Texture(GL gl, Span<byte> data, uint width, uint height)
	{
		//Saving the gl instance.
		_gl = gl;

		//Generating the opengl handle;
		_handle = _gl.GenTexture();
		Bind();

		//We want the ability to create a texture using data generated from code aswell.
		fixed (void* d = &data[0])
		{
			//Setting the data of a texture.
			_gl.TexImage2D(TextureTarget.Texture2D, 0, (int)InternalFormat.Rgb32f, width, height, 0, PixelFormat.Bgra, PixelType.UnsignedByte, d);
			SetParameters();
		}
	}
	public unsafe void Update(Image<Rgba32> image, uint width, uint height)
	{
		//See https://stackoverflow.com/questions/50025908/convert-imagergba32-to-byte-using-imagesharp
		//var memoryGroup = image.GetPixelMemoryGroup();
		//var mg = memoryGroup.ToArray()[0];
		//var pixelData = MemoryMarshal.AsBytes(mg.Span).ToArray();

		byte[] pixelBytes = new byte[image.Width * image.Height * Unsafe.SizeOf<Rgba32>()];
		image.CopyPixelDataTo(pixelBytes);

		Debug.Assert(pixelBytes.Length == image.Width * image.Height * Unsafe.SizeOf<Rgba32>());
		fixed (void* d = &pixelBytes[0])
		{
			//Setting the data of a texture.
			_gl.TexImage2D(TextureTarget.Texture2D, 0, (int)InternalFormat.Rgb32f, width, height, 0, PixelFormat.Rgba, PixelType.UnsignedByte, d);
			SetParameters();
		}
	}

	public unsafe void Update(Span<byte> data, uint width, uint height)
	{
		fixed (void* d = &data[0])
		{
			//Setting the data of a texture.
			_gl.TexImage2D(TextureTarget.Texture2D, 0, (int)InternalFormat.Rgb32f, width, height, 0, PixelFormat.Bgra, PixelType.UnsignedByte, d);
			SetParameters();
		}
	}

	private void SetParameters()
	{
		//Setting some texture perameters so the texture behaves as expected.
		_gl.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureWrapS, (int)GLEnum.ClampToEdge);
		_gl.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureWrapT, (int)GLEnum.ClampToEdge);
		_gl.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureMinFilter, (int)GLEnum.LinearMipmapLinear);
		_gl.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureMagFilter, (int)GLEnum.Linear);
		_gl.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureBaseLevel, 0);
		_gl.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureMaxLevel, 8);
		//Generating mipmaps.
		_gl.GenerateMipmap(TextureTarget.Texture2D);
	}

	public void Bind(TextureUnit textureSlot = TextureUnit.Texture0)
	{
		//When we bind a texture we can choose which textureslot we can bind it to.
		_gl.ActiveTexture(textureSlot);
		_gl.BindTexture(TextureTarget.Texture2D, _handle);
	}

	public void Dispose()
	{
		//In order to dispose we need to delete the opengl handle for the texure.
		_gl.DeleteTexture(_handle);
	}
}

[Perksey]

You need to use glViewport in your FramebufferResize callback to tell OpenGL to resize your framebuffer when the window size changes.

[maptz]

Thanks @Perksey for the super-fast response. You got it. It was as simple as adding the following code to my Start method:

_window.FramebufferResize += (obj) =>
		{
			_gl.Viewport(obj);
		};