iphone - Set background for 320 * 70 EAGLView

Question

I want to set the background image for 320 * 70 EAGLView (using openGL). I set

glOrthof(0, backingWidth, 0, backingHeight, -1.0f, 1.0f);

where backingWidth = 320; backingHeight = 70;

Sorry if my issue is obvious or some of the points are incorrect. The question is how to make the coordinates in a vertices array to set background properly. I'm new to openGL, but as far as I know these coordinates should be having degrees of 2. How should I set these coordinates to 320 and 70. I've investigated Apple's sample code of GLImageProcessing and they have 512 * 512 vertex array that covered 320 * 480 of the view. How can I relate 512 * 512 vertex array of ImageCoordinate on the screen to real coordinates?

This is my code, and now part of image is now shown:

// Clear the view
    glClear(GL_COLOR_BUFFER_BIT);

    glBlendFunc(GL_SRC_ALPHA, GL_ONE);

    glColor4f(1., 1., 1., 1.);

    glPushMatrix();


    glEnable(GL_TEXTURE_2D);
    glEnableClientState(GL_VERTEX_ARRAY);
    glEnableClientState(GL_TEXTURE_COORD_ARRAY);

    {
        // Draw our background oscilloscope screen
        const GLfloat vertices[] = {
            0., 0.,
            512., 0., 
            0.,  256.,
            512.,  256.,
        };
        const GLshort texCoords[] = {
            0, 0,
            1, 0,
            0, 1,
            1, 1,
        };


        glBindTexture(GL_TEXTURE_2D, bgTexture);

        glVertexPointer(2, GL_FLOAT, 0, vertices);
        glTexCoordPointer(2, GL_SHORT, 0, texCoords);

        glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
    }