I use an OpenTK GLcontrol as a faster alternative to GDI+ for displaying images and I would like to convert the old deprecated code to OpenGL 4 but I'm having trouble adapting code samples in guides I have found to my needs so would anyone kindly show me how to convert this:

GL.TexSubImage2D(TextureTarget.Texture2D, 0, 0, 0, rez.Width, rez.Height, PixelFormat.Bgr, PixelType.UnsignedByte, currentframe);
GL.MatrixMode(MatrixMode.Projection);
GL.LoadIdentity();
GL.Ortho(-1.0, 1.0, -1.0, 1.0, -1.0, 1.0);
GL.MatrixMode(MatrixMode.Modelview);
GL.LoadIdentity();
GL.Enable(EnableCap.Texture2D);
GL.BindTexture(TextureTarget.Texture2D, tex);
GL.Begin(PrimitiveType.Quads);
GL.TexCoord2(0.0f, 1.0f);
GL.Vertex2(-1.0f, -1.0f);
GL.TexCoord2(1.0f, 1.0f);
GL.Vertex2(1.0f, -1.0f);
GL.TexCoord2(1.0f, 0.0f);
GL.Vertex2(1.0f, 1.0f);
GL.TexCoord2(0.0f, 0.0f);
GL.Vertex2(-1.0f, 1.0f);
GL.End();
OGLControl.SwapBuffers();

Thanks for the advice, Is there by any chance a more direct way of drawing pixel data without scaling etc. with modern OpenGL?

There is sadly not but that is what makes "modern" graphics so flexible. You need to manage anything by your own from vertex management to the render/processing pipeline.

I did need a small class for debug code output in the past but even that needed a min of a vertex buffer to tell the graphics where are the pixel areas I want to write to, a texture holding thatever has to be shown (text in my case) and at least to shaders (vertex and fragment) to bring whatever up to the screen.

Matrix calculations are now no longer made by GL since you need to roll your own or use a library as mentioned because you need to transform every pixel by the shader for getting expected results. Passing an identity matrix does not do what you might expect here so calculating ortho or projection view is needed. OpenTK has this capability already so dont worry about that, just calc a matrix and load it into your shader.

Anything between begin and end needs to be put into a VBO/VAO once so making a general setup here saves you a lot of render time.

It might look like a mountain of work but it isnt and it is worth it

If you only want to get a big 2d pixel array to the screen your current code is just fine from a performance standpoint.

With OpenGL or D3D11 you can't access texture data directly and always neet to use a api copy command to get data into a texture before you can then get that texture onto the screen.

Only D3D12 and Vulkan give you the abbility to draw directly from client memory to the screen.

If you do blitting, like put you scene together by drawing many square images (sprites). Then it may be already worth to consider a more modern approche.

Edit: I hate forums that fuck up formating if your don't use javascript. -_-

I'd love to be able to use Vulcan but from what I've read its difficult even for an experienced graphics programmer to use and I can barely get my head around my bit of GL.