[NTG-context] Semi-transparent banners for a cover.

A project specifies that for the cover of a brochure there be a photograph as the background (doable in Context), and semi-transparent rectangles across the page highlighting the various strings of text. The rectangles darken but do not completely block out the underlying illustration. It is a layer cake, a photo, with semi-transparent rectangles laid across it, and type within the rectangles. This is a job more easily done in Gimp etc. but my question is, can it be done in Context at all? How do I create the semi-transparent elements? -- John Culleton Want to know what I really think? http://apps.wexfordpress.net/blog/ And my must-read (free) short list: http://wexfordpress.com/tex/shortlist.pdf