Luminance edge is a cue for glossiness perception based on low-luminance specular components.

Abstract

The visual system is considered to employ various image cues from an object image to perceive its glossiness. It has been reported that, surprisingly, even for object images without specular highlights we can perceive glossiness by relying on low-luminance specular components (Kim, Marlow, & Anderson, 2012). This type of perceptual glossiness is referred to as dark gloss. However, it is still unclear whether dark gloss is observed commonly across various objects, and what image features are cues for dark gloss. To address these issues, we performed several psychophysical experiments. First, we measured perceived glossiness for a number of computer-graphics object images with natural specular reflection components (Full condition) and for those without high-luminance components of specular reflections (Dark condition). The results showed that dark gloss (glossiness perception in the Dark condition) was generally observed on almost all object images, while its intensity was rather different across the images. Then we psychologically or computationally measured several image features for the stimulus images, such as luminance edge number, recognizability of reflection images, and some highlight-related features, to examine their relations to perceived glossiness with a multiple regression analysis. The results demonstrated that luminance edge number was most strongly related to glossiness scores among the measured features only for object images with potent dark gloss. These results suggest that luminance edges are an effective cue for dark gloss under certain stimulus conditions.