Placing visible text over images [on hold]

I'm trying to place text over an image. The text should be highly visible, and easily legible, yet professional looking. The problem is that the image is one of many, and I can't find a consistent text coloring scheme that keeps it visible in all of them. I've also tried playing with color inversion (text color is the image inverted), saturation, outlines, and a whole lot of other things. Is there a standard way of doing this that I'm just not aware of?

It may help to note that most of the images are relatively contrasty and somewhat grayscale. While that should make this rather simple (red and blue striped text for example) any colorful text really seems to throw out professionalism.

Also, the text itself varies from one word to five or so words, so not much. Because the emphasis is equally on the image and the text, the text has to be placed off to one side (probably the bottom) of the image.