Hide content underneath a transparent footer

For a client i make a wp site without header and the navigation in the footer, i have in the site a image background and the client wish to have the footer light transparant to see as much as possible from the background image. therefore the page container with content is also totaly transparent with an dark font color.

i have to find the sollution to hide the content behind the transparent footer, the footer is fixed on the bottom of the page.

any help appriciated