parallax bg

local function setUpBG()

    local bgGroup = display.newGroup()
    scene.view:insert( bgGroup )
    bgGroup:toBack()

    local bgImages = {
        { file = "filename1.png", width = width, height = height, x = x, y = y, speed = scalar },
        { file = "filename2.png", width = width, height = height, x = x, y = y, speed = scalar },
        { file = "filename3.png", width = width, height = height, x = x, y = y, speed = scalar },
        { file = "filename4.png", width = width, height = height, x = x, y = y, speed = scalar },
        { file = "filename5.png", width = width, height = height, x = x, y = y, speed = scalar },
        { file = "filename6.png", width = width, height = height, x = x, y = y, speed = scalar },
        { file = "filename7.png", width = width, height = height, x = x, y = y, speed = scalar },
    }

    for i = 1, #bgImages do
        local bgImage = bgImages[ i ]
        local image   = display.newImageRect( bgGroup, bgImage.file, bgImage.width, bgImage.height )
        image.data    = bgImage
    end

end

local function drawBG( x, y, bgGroup )

    for i = 1, bgGroup.numChildren do
        local child = bgGroup[ i ]
        local data  = child.data
        child.x     = data.x - x * data.speed
        child.y     = data.y - y * data.speed
    end

end