The fixing quality of printed images has been characterized by the adhesion strength between the image layer and the substrate, and by the cohesion strength within the image layer. A simple tape test and a crockmeter test have been widely used to evaluate adhesion and cohesion strength respectively. The demand for using other fixing quality test methods and more reliable assessment methods has been increased due to the extensive application of color printing, advances in printing technology, the use of a wide range of substrates, and inaccuracy and poor reproducibility of the tape and the crockmeter tests. Recently pen-offset, crease, bending and rolling tests have been widely used in the printing industry.An alternative crease test apparatus has been designed and constructed in the author's laboratory. The apparatus can apply either static or dynamic pressure on the image sample while the load is traversing on the back of the image. The authors have developed image-processing algorithms compiled into open source software to evaluate the crease line image. To characterize and quantify the test result, a crease test number (CTN) has been defined, which is a product of the grey level shift on the damaged image area and the width of the crease line. The crease test apparatus and in-house image processing software can provide more information with high reliability. It can be applied efficiently to examine the crease test performance of printing samples. And it can be a valuable research tool in the R&D stage of printing technology development.This paper will introduce the crease test apparatus and the methodology for analyzing crease line images using image processing technology.