Implementing a glossy button with OpenGL

I would like to implement a glossy button for GUI, something similar to this:

I started to code in plain C and using GDI, but I’m not satisfied of the results, so I’m trying with OpenGL.
I was wondering if something similar already exists or I must do it myself.
If I have to write it from scratch, have you some suggestions about implementing it?
I have an RGB array of a DIB section with the pixels of the background behind the button.
I created a GL_TEXTURE_2D with that data and now I have to apply alpha blend, shading and round rect shape, but I’m a bit confused how to proceede.