Contact angle is important in the study of many industrial processes, involving wetting, such as ink jet printing, lithoplating, coating adhesion, and floatation. Numerous methodologies have been developed for the measurement of contact angles. But there still exist many problems; in particular, there is no good method available for measuring contact angles of irregular liquid drop shape. To overcome these difficulties, we developed a method, Contact Angle Measurement of Arbitrary Drop Shape (CAMADS), based on image analysis, with edge detection in sub-pixel resolution. Comparing with other methods, CAMADS has a good combination of features: simple, reliable, flexible, and reasonably precise, in measuring contact angles; it can be applied to situations of asymmetric drop shape. CAMADS was demonstrated by studying the in vitro wettability of hydrogel contact lenses, and superior, excellent results were obtained in comparison with other existing methods.