issue with no way out…! (slab and text)

Hi all.
I have to face with a tricky problem:

I want to apply a slab to jit.gl.text2d.
So I texturized the gl.text2d.

My problem is the quality of the result: The text.dim is pretty poor, even with a texture's dim like 1200 1200…………

I am pretty despaired. Wouldn't it be possible to apply slab to text with a good resolution ??