Android Question Stamping Text on a Camera Photo With the Proper Text Color

Using canvas, I add a short text comment consisting of one line to a photo taken with the camera at the same position on the photo every time. How can I ensure that the comment is visible. The photo background can be dark or light depending on the photo taken. Is there a way to change the comment text color based on the photo background portion where the comment is positioned.
Thank you for any hints.

EDIT: I think I figured this out by adding a rectangle with while fill to the canvas, then add text with dark text color to the rectangle portion of the canvas. If you have a better solution, please offer it.