Computer vision is a field of computer science that works on enabling computers to see, identify and process images in the same way that human does, and provide appropriate output.
It is like imparting human intelligence and instincts to a computer. Image processing and computer vision are a little different from each other. Image processing means applying some algorithms for transforming image from one form to the other like smoothing, contrasting, stretching, etc.
While computer vision comes from modelling image processing using the techniques of machine learning, computer vision applies machine learning to recognize patterns for interpretation of images (much like the process of visual reasoning of human vision).