Quality Assessment of 2.5D Prints

Abstract

Technology is developing rapidly around the globe and advancing its capabilities in every industry. It can provide users with high-tech solutions to complex tasks.With the help of technology, industry, presently, can acquire natural-looking reproductions of a variety of materials and objects. Thus, technology allows to create a replica that is almost identical to the original version. The printing industry uses its technologies to provide customers with visually-appealing products. Elevated printing technology allows to add an elevation (i.e., height) to a 2D print. Such 2D print with surface elevation is called a 2.5D print. 2.5D printing (also called elevated printing) can fabricate natural-looking reproductions. Examples of 2.5D printing applications are packaging, signage, interior design, to name a few. It also has a high-end application area such as reproducing famous paintings for a variety of museums. Thus, it is essential to perform quality assessment to obtain high-quality 2.5D prints (reproductions). In other words, the quality assessment of 2.5D prints holds an important value for industry. Overall, quality assessment plays a vital role in most application areas. More specifically, both subjective and objective quality assessment are crucial in quality inspection of products. In this thesis, quality assessment of 2.5D prints both subjectively and objectively was investigated. For subjective quality assessment, several visual experiments were conducted where observers were given physical 2.5D prints for assessment. The research started with investigation of what quality attributes are relevant for quality assessment of 2.5D prints. The most used distinct quality attributes were found and they were proposed to be considered as the relevant ones for quality assessment of 2.5D prints. In order to be of high quality, prints need to have a natural look of the content they describe. Therefore, naturalness perception of 2.5D prints by focusing on effects of several relevant parameters was investigated. More specifically, the effect of elevation and surface roughness, the effect of elevation, and the effect of several ink types on naturalness perception of 2.5D prints were considered. There was impact by elevation on naturalness perception of 2.5D prints. It was found that the effect of elevation was content specific. Further, it was found that the optimal elevation that makes perception of naturalness of 2.5D prints was also content specific. In addition, 2.5D prints with matt inks were found to be perceived as more natural than with glossy inks by observers for specific content of images. For objective quality assessment, capability of existing metrics to assess quality of 2.5D prints was investigated. It was found that the tested metrics were capable to work with 2.5D prints under certain conditions. The research carried out in this thesis can benefit industry in designing both subjective and objective guideline(s) for quality assessment of 2.5D prints. This in turn can facilitate production of the high-quality and natural-looking 2.5D prints.