Scaling for a HUD

I am creating a HUD by drawing text and controls on a transparent BufferedImage, creating a texture from it and rendering it on a rectangle using orthographic projection.

It basically works, but I can’t work out how to do the scaling. What I want ideally is to create an image the same pixel size as the window, and have it scaled so it exactly fills the window.

Here is the code (JOGL)

    gl.glTranslatef(0.0f, 0.0f, -5.0f);
    gl.glColor4f(1.0f, 1.0f, 1.0f, 1.0f);
    gl.glOrtho(-1, 1, -1, 1, -1.0, 1.0);
    getTexture(gl, 128, 128);
    gl.glTexCoord2d(0f, 0f);
    gl.glVertex2f(-0.5f, -0.5f);
    gl.glTexCoord2d(1, 0f);
    gl.glVertex2f(-0.5f, 0.5f);
    gl.glTexCoord2d(1, 1);
    gl.glVertex2f(0.5f, 0.5f);
    gl.glTexCoord2d(0f, 1);
    gl.glVertex2f(0.5f, -0.5f);

getTexture creates and binds the texture. Any hints on how to scale it?

I find that I need to do a translate in the negative z direction to see anything. The smaller that translation, the bigger the image except that for values smaller in magnitude than -5 the texture disappears.