There is no way the search engines can detect this. The hidden text will however be visible for people who has disabeled the option of showing images in the browser (in order to load pages faster).
If someone checks your page (cometition) and turn you in you might be punished by the engines. If you are in a competative market your listing may be gone very soon.
In my opinion it`s usually safest playing within the rules of the engines.
