Color Authenticity for the Sustainable Development of Historical Areas: A Case Study of Shiquan

By inergency On Mar 15, 2024

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1. Introduction

1.1. Problems Existing in Historical Areas

As the treasures of a city, “historical areas (historical districts)” are areas with concentrated distributions of architectural heritage. As witnesses to the history and splendid culture of a city, they also have extremely high protection value. However, in China, historical areas often face a series of challenges [1,2]. Firstly, the color authenticity of historical areas is mainly reflected in the protection of the original architectural culture. In the process of protecting and developing historical and cultural blocks, some regions have neglected the overall inheritance of local traditional architectural culture, resulting in the loss of “authentic” cultural features in the newly built historical and cultural blocks [3]. In this case, the colors of the blocks may be unified, resulting in the loss of the original historical and cultural connotations in terms of facade colors [4]. This distorted color not only deprives the uniqueness of historical areas but also greatly undermines the sustainability of their historical value [5]. Secondly, excessive commercial development is also an important factor affecting the authenticity of color in historical areas [6]. Commercial development tends to change the original colors of blocks, making them look similar and undermining their historical sustainability [7]. For example, in order to attract tourists, some blocks may choose to use bright colors while ignoring the original historical colors, which not only affects the visual effect of the blocks but also damages the historical and cultural continuity. Excessive commercialization makes the colors of the historical areas simple and lacking in vitality, thus losing the original living atmosphere [8]. At the same time, the loss of residents in historical areas can also affect their color authenticity [9]. Due to the damage to the original living environment during the renovation process of some historical areas, many indigenous residents have to leave, and the population loss leads to the hollowing out of the old streets. Moreover, the subsequent revitalization continues to carry out the commercial-oriented transformation, which makes the colors of the blocks lose their vitality, further degrading the features of the blocks.

1.2. Color Authenticity of Historical Areas

In the field of urban planning and conservation of historical areas, the color authenticity of historical areas is an important topic [10,11]. This authenticity is not only reflected in the authenticity of the architectural style, cultural connotations, and community life but also in the authenticity of the colors. Colors, as an important element of historical areas, are an important manifestation of their authenticity [12]. The architectural colors of historical areas often retain their original color features, such as old red brick walls, time-honored blue flagstone (Qingshiban) pavement, and unique local cultural colors [13]. These color features are an important reflection of the color authenticity of historical areas and are also an important component of their historical and cultural value [14]. In the study of architectural color in historical areas, it has been found that different historical periods, geographical environments, and cultural backgrounds can all affect the architectural colors of historical areas [15]. For example, the historical areas of northern China in ancient times were often dominated by red and yellow colors. This is because the northern cities tended to be chosen as the capital cities of ancient Chinese dynasties, when red symbolized auspiciousness and yellow symbolized imperial power. On the other hand, the historical areas in the south of the lower reaches of the Yangtze River, mainly known as the Jiangnan region, may be dominated by white and gray colors because, in the architectural tradition of the Jiangnan region, white and gray are considered the colors closest to traditional Chinese ink painting. In addition, the architectural colors of historical areas will also be influenced by their functions and users [16]. For example, the architectural colors of commercial areas in historical areas may be more diverse and lively to attract customers, while the architectural colors in residential areas may be warmer and more comfortable to create a livable environment [17]. Therefore, the architectural colors of historical areas reflect not only their history and culture but also their functions and users’ needs [18].

The protection and restoration of colors is an important task in the sustainable development of historical areas. Usually, detailed investigations and records of the architectural colors of historical areas are required to understand their original color features and changes [18]. Then, based on these investigations and records, a reasonable protection and restoration plan is developed to maintain the authenticity of the architectural colors of the historical areas [19]. It is noted that in the process of protecting and restoring architectural colors, protection and restoration do not mean being the same. On the contrary, attention should be paid to modernization needs and development possibilities while preserving the authenticity of the architectural colors of historical areas. Therefore, the protection and restoration of architectural colors should be a sustainable process that not only respects history but also looks up to the future [20].

1.3. Quantitative Methods for Exploring True Colors

Under such a background, it is meaningful to explore the true color patterns in historical areas from the perspective of sustainable development [21,22]. China has its own traditional color spectrum, and these colors are also widely used in historic buildings. Exploring the colors of various parts of traditional architecture and the color patterns of buildings in historical areas plays a positive role in the sustainable development of historical areas. In recent years, the advancement and development of computer technology have provided new possibilities for research related to color visualization of historical areas, and the extraction of environmental colors has shifted from manual color selection tools to computer image processing technologies, including but not limited to mining methods for multi-sample urban data, flat image processing methods supported by machine learning technology, and color extraction applications supported by programming technology. More and more scholars are also trying to explore the correlation between digital media technology and the color visualization of building facades in historical areas using multiple methods. In terms of computer image processing, Gouaich et al. [23] established an HSV color space model, summarized the color composition of the M’zab Valley and Ksourian landscape in Algeria, and proved that the Ksourian landscape and M’zab Valley had strong color consistency, providing approaches to the restoration of urban architectural heritage and regional feature color extraction in natural environments. Yadav and Saraswat [24] compared the K-means clustering algorithm, fuzzy C-means clustering algorithm, Henry gas solubility optimization algorithm, chaotic gravity search algorithm, and J-segmentation methods and confirmed that the K-means clustering algorithm performed better in cutting a large number of samples, providing methods for the extraction and application of color visualization. Based on Bertin’s semiotics theory, Jégou et al. [25] combined the theories related to aesthetic and graphic designs, explored image colors through computer tools, formed and generated multiple gradient colors, and applied them to the fields of plane composition and color application in design. In terms of the acquisition of architectural samples, Zhong et al. [26] proposed that street-view images could be used as a carrier for identifying and extracting the dominant color tones of urban buildings. Fu et al. [27] used street-view photos as samples to extract the architectural colors in the main urban area of Changsha, China, and analyzed their color patterns. In terms of the optimization of color sample extraction methods, Miao et al. [28] replaced the traditional handheld cameras with ArcGIS and Python platforms to collect samples and completed large-scale mining of architectural element samples on Zhongyang Street in Harbin, China, improving data acquisition speed. As for color clustering method selection and application, Wu et al. [29] used K-means clustering to complete the color visualization of traditional Chinese painting and applied the clustering results to related designs, achieving a tight connection from concrete objects to specific designs. As for the specific color design methods, Chen et al. [30] constructed a complete system of traditional Chinese color schemes integrated with screening, application, and post-evaluation based on the PCSS color system and related clustering methods.

However, current research mainly focuses on exploring methods and approaches in a single field, and there is still a lack of interdisciplinary linkage thinking. At the same time, some methods and approaches are still not complete. For example, when obtaining and preprocessing large-scale samples, attention is only paid to the number of samples but not the quality of the samples; uncorrected architectural street-view samples make it difficult to restore their original colors, and inadequately trained datasets make it difficult to fully and accurately segment various color elements, which can directly lead to inaccurate experimental results and thereby affect the construction of subsequent color application strategies. Therefore, when focusing on the application of computer vision image processing technology supported by multi-source data, it is necessary to make each step as systematic as possible in order to make the color visualization results more accurate and objective.

After an in-depth analysis of recent academic literature, we found that the k-means clustering method has a significant advantage in the application of image color clustering. The superiority of the k-means clustering method is mainly reflected in the following aspects: Firstly, the algorithm steps of the k-means clustering method are concise and clear, making it easy to implement and understand, which makes it highly operable in practical applications. Secondly, the k-means clustering method performs well in terms of computational efficiency, especially when dealing with large-scale datasets. Its convergence speed is fast, and the clustering effect is good, which is of great significance to the needs of the big data era. In addition, the k-means clustering method has good flexibility and can be applied to different types of data and problems through various improvements and optimizations. Particularly when the sample data are dense and the difference between classes is obvious, the effect of the k-means clustering method is particularly outstanding. In this study, we need to cluster multiple target elements separately and in total, so we chose the k-means clustering method as the main research method to support our experiment. This choice is based on the above advantages of the k-means clustering method, as well as its wide recognition and successful cases in practical applications. We expect that by using the k-means clustering method, we can obtain more accurate and deeper research results.

Given the above situations, it is easy to find that historical areas, as important carriers of the living environment and urban culture, not only carry out daily residential functions but also reflect the expression of regional culture. As newly emerging technologies and media, multi-source data and computer vision image processing methods provide technologies for large-scale sample acquisition and digital image processing, which can be used to explore the visual interaction of regional architecture. On the other hand, as an intuitive carrier of regional cultural expression, architectural colors not only carry regional cultural information but are also closely related to the experiences of people. This study investigated the methods for the extraction and application of colors in historical areas. Through acquiring the street-view photo samples, processing the street-view photo samples, and clustering the colors of the street-view photo samples, this study aims to provide ideas for color control in historical areas, color selection and application in the designs related to historical areas, and methodological insights for academic research practices such as color management and sustainable development of historical areas.

4. Discussion on the Application of Traditional Chinese Colors in Suzhou Historical Block

Chinese traditional colors are rich and colorful, each with its own specific cultural and symbolic significance. In the historical areas of Suzhou, these traditional colors are widely used in traditional architecture, endowing buildings with unique beauty and cultural connotations [35]. We chose to compare the main findings of the color of the research area with the traditional Chinese color card mainly because Suzhou Shiquan Street, as a famous historical street in China, should reflect the consistency of the traditional style of ancient China. In ancient China, when craftsmen painted the exterior of buildings, they usually referred to the traditional Chinese color card. Although some historical materials have recorded the color of the building, these records do not fully reflect the accurate color scheme of the area. Therefore, we need to infer the current situation and find the color closest to the traditional Chinese color card in order to find out the color rule of Suzhou Shiquan Street and improve the color system of the entire block.

In addition to accurately understanding and restoring the architectural colors used in ancient Chinese architectural spaces, we should also delve into the meaning behind the colors. Why choose the color in the main findings? Compared with other colors, what are the advantages of the color in the main findings? By further studying these issues, we can strengthen our understanding of the main findings. At the same time, understanding the meaning behind the color in the main findings not only helps to enhance the sustainability of the entire block but also allows the vitality of the historical area of Suzhou Shiquan Street to continue. These are also important directions and goals of research.

(1): Colors of building facades

Through the visualization of colors, it is easy to find that pure white, bright white, and bluish white are the three colors widely used in architecture. White, as the most frequently used building color, is widely used in facade colors [36]. Firstly, from the perspective of visual culture, white has profound symbolic significance in traditional Chinese culture [37]. In the Five Elements Theory, white represents gold, symbolizing purity and nobility [38]. In Taoism, white symbolizes detachment and purity. Therefore, white is widely used in traditional architecture in the Jiangnan region, aiming to create a pure, elegant, and transcendent atmosphere. In addition, the white walls complement the natural environment of the Jiangnan region. Jiangnan region has four distinct seasons, and white walls can reflect the colors of the four seasons, integrating buildings with the natural environment [39].

Secondly, the application of white walls also has practical considerations [40]. The reflective performance of white walls can also improve indoor lighting, making the interior brighter [41]. In addition, the materials used for white walls are generally lime and white clay, which have good breathability and moisture absorption, thus effectively regulating indoor humidity and preventing wall dampness. At the same time, these materials are also common in the Jiangnan region, so they are easy to obtain, which reduces the cost of construction.

(2): Colors of the door header

Agate, coal black, light red, and reddish brown are colors widely used for door headers and exterior wall decoration, forming a sharp contrast with the white colors of the building facades [40]. Firstly, the widely used door headers in traditional architecture in the Jiangnan region hold unique significance. In traditional Chinese culture, agate and coal black symbolize solemnity and stability, while light red and reddish brown symbolize mystery [41]. They are in a sharp color contrast with pure white, bright white, and bluish white, creating a street style similar to Chinese painting. From the perspective of visual effects, the door headers with agate, coal black, light red, and reddish brown are not only a visual feature of traditional architecture in the Jiangnan region but also a symbol of the culture and society of the Jiangnan region [42].

Secondly, agate, coal black, light red, and reddish brown can summarize the colors of wood, which is a type of widely used material in traditional Chinese architecture [43]. These colors not only reflect the colors of wood in Chinese architecture but also often serve as natural paint colors for the anti-corrosion of wood. In addition to creating a solemn, stable, and mysterious atmosphere, wood also has good insulation and moisture absorption properties. Due to weather conditions, the combination of wood and paints can effectively regulate the temperature and humidity of buildings [44], prevent cracking and deformation of door headers, effectively prevent direct sunlight exposure, reduce heat absorption, and lower the temperature of the door headers, thereby extending the service life of the door headers [45].

(3): Colors of the environmental atmosphere

Under normal circumstances, environmental colors are not fixed and are difficult to capture [46]. However, in this study, the colors captured through street-view photo samples are compared with traditional Chinese color cards, providing a concrete summary of the environmental colors of the historic blocks of Shiquan Street in Suzhou. The environmental colors include green onion, stone green, mellow yellow appearing on street plants, stone blue, and indigo blue appearing in the sky [47], as well as red golden, pale yellow, and tan golden yellow appearing in other surroundings, which are all classic and traditional Chinese colors [48].

As the commercialization of historical areas becomes increasingly severe, most of the buildings located within the blocks are adorned with attractive signs or slogans [49]. The emergence of these commercial elements is extremely detrimental to the creation of the traditional atmosphere of historical areas and undermines the continuity of their interfaces. Therefore, concretizing the presentation of environmental colors, which are difficult to capture, also provides an important basis for the selection of modern commercial colors at the interface of historical areas [50]. In the inevitable process of commercialization, it is necessary to maintain the original environmental color of historical areas as much as possible to maintain the authenticity of their historical appearance [51]. At the same time, consideration should also be given to the uniqueness of colors, which should present features that are easy to attract investment and customers without damaging the overall street interface [52].

5. Conclusions

The contradiction between the rapid progress of urbanization and the sustainable development of historical areas has posed new challenges to the conservation and revitalization of cultural relics and buildings in China. How to achieve a balance between the continuation of traditional style and modern commercial development has become a research focus, especially in the typical historical areas of the Jiangnan region in China. This article takes the historical areas of Shiquan Street in Suzhou as an example and proposes a visualization method and optimization strategy for the architectural colors of the historical and cultural blocks of Shiquan Street in Suzhou. Based on the typical case, the main findings and inspirations are as follows:

(1): Adhering to and carrying over traditional color

Scientific and reasonable color control can integrate commercial elements into the overall environment while presenting a certain aesthetic, better conveying a more comprehensive and comfortable visual effect to the audience [53,54]. In urban planning and design, we need to consider how to leave space for valuable contemporary commercial elements in urban street spaces. This is crucial to avoid a bias that is solely centered on history. We need to realize that modern commerce and traditional architecture are symbiotic; they are also the products of tradition and modernity and can enhance the commercial atmosphere of the city and increase the attractiveness of the city. Therefore, when considering the design and planning of urban street spaces, we should not only focus on the traditional use of color in architecture but should also consider using traditional colors as a bridge to connect modern commercial elements with traditional architecture. Therefore, how to use these colors based on historical blocks to create attractive commercial elements is crucial, rather than abandoning the appearance of these commercial elements in order to overly pursue harmony, unity, and color balance. This is why we need to first find the color rules of historical blocks and then cluster them specifically. How to choose colors for these commercial elements within the traditional color range so as to ensure that the entire historical area exudes new commercial vitality within a controllable color atmosphere is the key issue we need to consider. The establishment of color models plays a positive role in reshaping and maintaining the original cultural atmosphere of urban scenic spots and historical areas [55]. The traditional colors of Suzhou are an important component of its historical and cultural heritage. For example, the colors commonly used in traditional architecture in Suzhou, such as pure white, bright white, bluish white, agate, and coal black, can highly summarize the color impression of “green tiles and white walls” in Suzhou’s traditional architecture. This traditional color combination conveys a stable historical architectural intention. Therefore, in the selection of colors, it is necessary to uphold such color combination tradition, closely adhere to the color intention, ensure that the color information conveyed is in line with regional culture, and integrate it into the design so as to carry over the traditional color style of Suzhou, inherit and promote the architectural color culture, and thereby achieve the sustainable development of historical areas.

(2): Expanding and innovating color combinations

Color design is an important element of building facades, and architecture is a visual representation of regional culture. Color aesthetics, as an art system that studies the relationship between color visual expression and culture, can enhance the visual beauty and cultural atmosphere of design objects through its application [56]. On the basis of maintaining the original color impression of “green tiles and white walls” in Suzhou, expanding and matching the design colors can achieve innovative color design without departing from the original color style of the design object. For example, as shown in Figure 8, artistic matching of the color particles within a controllable range of H values can ensure the original impression of color while obtaining more color design choices. While respecting and retaining the traditional color style of Suzhou, the innovative color matching can make the design have both traditional color style and innovative color design and make the audience’s experience not easily detached from regional culture. Therefore, it is necessary to further utilize the cultural transmission and emotional interaction features of colors to achieve the expansion and innovation of color matching on the basis of fitting the decorative and functional features of architectural colors [57]. This method not only retains the color impression of traditional culture but also endows design works with new visual effects and aesthetic experiences, making it an innovative method that respects tradition.

(3): Establishing and planning color system

At present, the main problems faced by Chinese cities are the loss of urban features and the dilution of urban culture, which are reflected in the chaotic color management and pollution of urban interface colors [58]. Under such circumstances, it is difficult to ensure the authenticity of historical areas, and it is also difficult to continuously exude their unique charm in the city. Therefore, from a macro perspective, a color design system that highlights regional culture and regional style should be established, and the urban color-featured areas should be planned. From a micro perspective, a regional featured color model should be scientifically established for urban historical and cultural blocks, and its color patterns should be summarized. It is necessary to improve the color quantification technology to effectively control urban colors [59]. At the same time, a central color card should be constructed to achieve the goal of quickly selecting colors and fitting the regional style to the greatest extent possible, thereby achieving a transformation of regional colors from sensibility to rationality and from qualitative to quantitative.

(4): Innovation of this article

As for the methods selected in this article, the combination of open-source platforms, ArcGIS, and Python scripts can quickly and efficiently cope with the acquisition of large-scale historical street-view photo samples, improving experimental accuracy and speed. Secondly, Matlab can perform batch color space interpretation of digital images and quickly construct visual color models. The excellent data visualization and color clustering capabilities of Matlab provide opportunities and possibilities for the data processing of a large number of street-view sample photos. Finally, compared with various color extraction methods, the strategies for obtaining and selecting environmental colors in historical areas summarized by the above methods are faster, more efficient in completing color extraction, and can make the design colors of historical areas tend to be localized within a controllable color range, highlighting the regional uniqueness of colors. In addition, the colors obtained in this article are compared and coupled with traditional Chinese color cards, figuring out the traditional Chinese colors commonly used in architectural decoration, which not only provides relevant color strategies for maintaining the overall color style of Shiquan Street in Suzhou but also provides corresponding references for historical areas of the same style and type in the Jiangnan region of China.

(5): Limitations of this study

This study has some obvious limitations in terms of the quality of the street-view photo samples. Firstly, because street-view images are mainly used to meet the needs of street navigation, the clarity of the samples may not be high during the process of large-scale continuous shooting. This is an unavoidable problem, as we must find a balance between obtaining enough visual information and maintaining image clarity. Secondly, the samples are affected by lighting and shadows, resulting in a cold overall color temperature. This is a common problem in all street-view photo samples from open platforms. Although we have performed a unified color correction on them, it is difficult for us to accurately correct each sample due to the different lighting conditions and shadow effects of each sample. In addition, the samples are also affected by greening obstructions, which lead to incomplete coverage of buildings during semantic segmentation, thus producing other color particles. This is an unavoidable problem, as we cannot control the shooting environment of street-view images. Finally, the samples are also affected by seasonal factors. For example, the color tone and saturation of samples may tend to be cold in the spring environment, affected by the weather. Although this paper deals with this problem by uniformly adjusting the samples, it may cause overexposure to some samples.

In response to the above problems, we can currently only compare street-view photo samples provided by multiple open platforms and select them by balancing multiple elements such as time period, weather, season, and research objects. We recognize that finding a more scientifically accurate image correction method will help us perform color clustering and extraction more accurately. Despite these limitations, we believe that the results of this study still have important significance and provide valuable references for future research. We look forward to future research being able to solve these problems and further improve the accuracy of street-view image analysis.

The traditional Chinese color card was widely used in ancient Chinese architecture for facades, utensils, furniture, ornamental porcelain, Chinese paintings, etc. Different from the color system commonly used internationally today, each color in the traditional Chinese color card has its own unique name and meaning. For more details on the traditional Chinese color card, please visit: http://zhongguose.com/ (accessed on 2 February 2024).

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