Virtual reconstruction of the painting process and original colors of a color-changed Northern Wei Dynasty mural in Cave 254 of the Mogao Grottoes

The Northern Wei Dynasty (386–534 CE) murals of Cave 254 in the Mogao Grottoes, China, have been extensively affected by pigment color changes and fading. These issues severely hinder efforts to correctly understand the value and painting process of murals from this historic period. The virtual reconstruction of faded murals could help researchers gain an understanding of their pigment chemistry and painting processes in a virtual environment and provide a visual reference for conservation and art studies. However, simple virtual reconstructions may not be accurate owing to deficiencies in our understanding of the color-changed pigments and fading of image lines. In this study, a minimally invasive approach was used to elucidate the details and pigment distributions of a faded mural. Technical photography was performed to obtain infrared-reflected false color, ultraviolet-reflected false color, and ultraviolet luminescence images of the mural. Noninvasive and minimally invasive analyses were then performed on localized parts of each color-area to identify their pigments and paint stratigraphy and construct a hue–saturation–brightness color palette for these pigments. Finally, the pigment analysis results were combined with multispectral image features to determine the pigment distributions of the mural, which were then used to virtually reconstruct the original color and appearance of the faded mural under ideal conditions. This study is the first to use a virtual reconstruction based on objective analyses to simulate the original color, painting processes, and pigment stratigraphy of a mural from the Northern Wei Dynasty. A preliminary discussion of the relationship between the painting processes of the mural and color changes in its pigments was also performed. The findings of this study will provide new perspectives for the study of Northern Wei Dynasty murals.