What are the images? What constitutes a scribble? Are the requirements specific, or is it necessary to find any scribble on any image?
Do the marks have clear boundaries? Are they a distinct color from the background? Are there similar marks which are not "scribbles"?
Are the marks transparent or feathered?
Is it possible that marks are not distinctly colored?
Does image size or quality impose practical restrictions?
Did you notice that every part of this answer is actually a question, and that this is the most anyone has bothered to say in nine years? This concludes the lesson.
