A novel approach for assessing color harmony of historical buildings via street view image

While new buildings continue to emerge in the process of urbanization, historical buildings, as valuable legacies carrying national historical memory, play an important role in the urban landscape. Previous studies have shown that color harmony is a crucial factor in coordinating urban landscapes. However, the evaluation of color harmony in historic areas and buildings lacks effective quantitative standards, often overlooking factors such as complementary color harmony and the compatibility of analogous colors. This study aims to build a new method to evaluate the color harmony of historical buildings through street view technology, semantic segmentation algorithms, quantification of color harmony methods based on image property detection and classification, questionnaire verification, and takes Shanghai's historical buildings as an example to explore. Our study categorizes six types of color harmony indexes for Shanghai street-facing historic buildings into three levels, with the top tier serving as a benchmark for excellence and the lowest tier highlighting areas in need of urban environmental improvement. This study uniquely considers color compatibility within hue ranges and expanded relationship types like complementary harmony. This approach, applicable to cities globally, offers practical tools for urban planners and conservators in managing and preserving historic areas and buildings.