It is economically important for manufacturers of high-temperature machines to be able to measure creep damage so they can predict residual service life more accurately. This paper describes and refines an image analysis method for evaluating creep damage in laboratory test pieces. It is a preliminary study of how to extract relevant information for damage measurement by cavities counting. Grain boundary extraction, which is directional information, is the major question to be overcome before measurement can be automated. The search for a crest-line extraction filter by the Canny method has led to the development of a directional wavelet transform filter. The results of this innovative filtering method are applied here.