This paper presents an algorithm for correcting the distortion of a wide-angle lens with a single image. The radial distortion that transforms the horizontal and vertical lines in the real world into general curves in an image provides us with an image of degradation. Based on the principle that straight lines in the real world look straight in an image under the pinhole camera model, the proposed distortion correction algorithm extracts curves automatically and manually, fits lines to the curves, and determine the optimum distortion parameters by exploiting the Levenberg-Marquardt algorithm (LMA). Ultimately, the distortion parameters convert distorted images into undistorted ones without degradation of image quality.