An Integrated Repainting System for Digital Restoration of Vijayanagara Murals

Abstract

An integrated repainting system is proposed in this paper for digital restoration of images of heritage murals, which have historical significance in their painting styles and ritualistic contents. The repainting system uses an ensemble of conventional image processing tools, in tandem with some state-of-the-art image rendition techniques, such as scaled bilateral filtering, source-constrained inpainting, tonal processing, and texture mapping based on gradient fusion. Murals that are old by nearly four centuries, have been imaged in situ from the walls of temples under a controlled environment, and then they have been fed to our repainting system. As the work of mural art is highly subjective, and so is its interpretation, a battery of tests for subjective evaluation has been performed to compare the different stages of restoration. Three different tournament strategies have been followed to make the test result devoid of any subjective bias as far as possible. The overall evaluation result is quite encouraging, as the restored images exhibit a gradually improving quality through the different stages of restoration.

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

“…In the 365 nm-excited UVL image, the darkbrown area has a weak salmon luminescence similar to that of the light-red area (Fig. 6d [7,8]) (full-scene multiband image A1 in Additional file 1). Microsamples were obtained from damaged parts of the mural in Scene 2 (i.e., the black edges of the mountain range and the darkbrown pigment layer on the edges of the human characters' clothes).…”

“…The VISR images showed that the mural currently has 10 color systems, including Fig. 3 Partial-view VISR imaging of the Prince Sattva mural and 10 analysis points blue (1), bean green (2), ivory white (3), pure white (4), light red (5), charcoal gray (6), Black-brown (7), maroon (8), deep red (9), and red-brown (10). Because some of these colors, such as black-brown, maroon, deep red, and red-brown have a similar appearance, they are difficult to distinguish.…”

“…As the color and appearance of the black-brown and maroon parts are very similar, delineating their color boundaries in the VISR image (Fig. 3d [7,8]) is difficult. However, the IRRFC image shows a small difference in the IR reflectance of these color areas.…”

“…Based on the pDM observations, the black-brown area has a dark-brown pigment layer covered by a layer of black-gray matter (Fig. 7a [7]). The pXRF analysis shows that the black-brown area contains high concentrations of Fe and As, as well as Ca (Fig.…”

“…An example of a replication being used to reconstruct a mural is the "Donor portrait of Lady Wang from Taiyuan in worship" from Cave 130, which was replicated by Duan Wenjie [6]. Virtual reconstruction, an approach that is currently in vogue, refers to the use of computational image processing algorithms, such as image segmentation, texture synthesis, machine learning, and neural networks, to digitally reconstruct the color and details of an artistic product [7][8][9][10][11][12]. These methods could inform and pave the way for future attempts to recreate the original appearance of ancient murals.…”