An on-line computer system for measuring a deformation of a diffuse object with a speckle interferometer is presented. Methods for evaluating a speckle interferogram using digital image processing techniques are also discussed. The system consists of an interferometric optical setup and a computer TV-image processing facility. A speckle interferogram is generated by arithmetic operation between two digitized speckle patterns before and after deformation of the object. The informations about the deformation are extracted by two modes of procedures in analyzing the interferogram. One of them is a method for automatic analysis using digital image processing techniques such as gray scale modification, linear spatial filtering, thresholding, and skeletoning. The alternative is a man-machine interactive method for a simple and high-speed processing of the interferogram by using a light-pen facility. The determined fringe order numbers are interpolated and differentiated spatially to give strain, slope, and bending moment of the deformed object. Some examples of processed patterns are presented.