Loading an OpenGL image can be done in 5 lines of code.
Bitmap bmp = new Bitmap("SomeImageFile.png");
BitmapData bmp_data = bmp.LockBits(new Rectangle(0, 0, bmp.Width, bmp.Height), ImageLockMode.ReadOnly, System.Drawing.Imaging.PixelFormat.Format32bppArgb);
GL.TexImage2D(TextureTarget.Texture2D, 0, PixelInternalFormat.Rgba, bmp_data.Width, bmp_data.Height, 0, OpenTK.Graphics.OpenGL.PixelFormat.Bgra, PixelType.UnsignedByte, bmp_data.Scan0);
bmp.UnlockBits(bmp_data);
bmp.Dispose();
Three of these 5 lines are just fillers. This is the only line that matters:
GL.TexImage2D(TextureTarget.Texture2D, 0, PixelInternalFormat.Rgba, bmp_data.Width, bmp_data.Height, 0, OpenTK.Graphics.OpenGL.PixelFormat.Bgra, PixelType.UnsignedByte, bmp_data.Scan0);
Make sure you understand the paramaters of the GL.TexImage2D
function, as it is what uploads the large array of pixel data to the GPU.
The loading code is mostly copied from here