1. An image correcting method comprising: selecting a first region in an image comprising non-overlapping first and second regions; removing a speckle from the second region, by using image information associated with a predetermined frequency band; and increasing brightness values of pixels of the first region by mapping, to a first predetermined brightness value, a brightness value associated with a largest quantity of pixels among the pixels of the first region, and decreasing brightness values of pixels of a region of a speckle by mapping, to a second predetermined brightness value, a brightness value associated with a largest quantity of pixels among the pixels of the region of the speckle.