# Visual Sensing Technology for Digital Image-Oriented Public Art Design

Authors: Pei Zheng; Hongyan Cong
Journal: Security and Communication Networks
 (2022)

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## Abstract

With the development of computer software technology, computer image processing software has become increasingly significant in the public art design process. It can help with graphic design inventiveness and color presentation, as well as improve the aesthetics of public art design. This study aims to analyze the use of digital image synthesis and visual sensing techniques in public art design, as well as to use Dongba paintings, which reflects Chinese culture, as image fusion research objects. The Dongba painting’s line drawing is modeled and drawn, and an element library is created. The characteristic information of Dongba paintings is extracted using line integration convolution (LIC) algorithm. The background texture elements of the image are fused using image quilting texture’s improved synthesis algorithm. To improve the image effect of the linked Dongba paintings, a local color transfer algorithm based on color transfer rights is presented. The results show that the optimized synthesis algorithm of image quilting textures can achieve the same texture synthesis effect as the original algorithm. The method can meet the needs of real-world applications while also significantly improving the original technique’s performance. The synthesis time is reduced by 87.67%, and the image recognition accuracy of the local color transfer algorithm reaches 88.9%. Compared with other algorithms, the recognition accuracy is improved by 6.4%. The proposed digital image synthesis technique can create good images with different foreground and backdrop combinations and can provide a diverse visual expression. This contributes to public art’s visual production.


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## Body

## 1. Introduction

More authentic and gorgeous visual art effects are pursued by people with the development of computer technology. Compared with traditional synthesis, digital image synthesis employs modern computer graphics ideas and procedures. Science, technology, and art have long been key yardsticks for measuring human society’s progress [1]. Science and technology represent the pinnacle of human comprehension, application, and alteration of nature, whereas art symbolizes the pinnacle of human understanding, harmony, and societal yearning. Technology and art collide in this state, and the value is prominent in the practice of fusion. Computer image processing technology is a technological revolution carried out by art as a tool and means. It excavates personal personality and inner feeling to a greater extent for artists, and it excavates personal personality and inner emotion to a greater extent for ordinary people [2]. It lowers the threshold for art, popularises the concept of art, and organizes human beings’ aesthetic sense and volition. Computer technology continues to advance, and many bold and reasonable stories are being told with it and art. The use of computer image processing technology in art creation not only exposes art practitioners to a new gospel but also allows the general people to participate in impromptu art creation. It has grown in popularity as a new creative process with a broad and far-reaching impact on art creation [3].Dongba paintings are representative of Yunnan’s Naxi minority traditional culture. Its unique artistic characteristics are sought after and studied by the painting circle [4]. The influence of Chinese culture on world culture has become more and more extensive. Combining paintings with Chinese characteristic artistic styles and computational image synthesis technology can promote the advancement of digital culture and produce a new form of visual expression. Dongba painting is different from the traditional painting style and is essential for Naxi minority culture and art. The paintings are spread in the Old Town of Liang, Yunnan Province, and the Naxi minority of Yulong autonomous county [5]. Dongba paintings mainly include wooden sign paintings, scripture paintings, card paintings, and scroll paintings and are based on folk gods, legendary ancestors, and animals of the Naxi minority. The works are vivid and straightforward, with ingenious design. Many paintings also retain the vital characteristics of hieroglyphics and calligraphy and are the “living fossils” for studying human primitive painting art. Dongba paintings are used as the original material for digital image synthesis [6].Scholars have extensively studied the application of digital image synthesis technology in designing public arts. Thies et al. [7] introduced delayed neural rendering. This is a new paradigm of image synthesis. Traditional graphics channels are combined with learnable components. They recommend training neural texture as part of the scene capture process. Similar to conventional textures, neural textures were stored as three-dimensional mesh maps. After end-to-end training, the method can also synthesize realistic images. Chu et al. [8] proposed combining a multiview system and synthetic aperture system to improve the measurement level of small-scale or long-distance objects. The multiview system records the parallax information. The effective aperture was increased by synthesizing several light holes of the multiview system to obtain a higher optical resolution image. The higher resolution image was fused into the retinal image, and the measurement result was greatly improved. The authors in [9] designed a procedure to evaluate a single generated image. When humans judge the quality of an embodiment, the spatial content will attract more attention to the generated image. An efficient machine learning model that combines pixel-level and spatial functions is proposed. Tong [10] introduced the omnidirectional vision sensor, art design image, and sensory experience modes and analyzed the six aspects of image database dependency test, performance, comparison of different distortion types, false detection rate and missing detection rate, algorithm time-consuming comparison, sensory experience analysis, and feature point screening. Svetlichnaya [11] investigated numerous artistic activities aimed at adapting an individual’s existing outward image to various social and cultural settings. The use of art design to shape a person’s external appearance is positioned as a “flexible” image model in communication. Huang et al. [12] proposed a method for synthesizing texture images based on discrete example-based elements and extracted texture feature distribution from exemplars and then produced discrete elements based on the clustering algorithm. Dong and Zhou [13] proposed a texture synthesis quality assessment method and introduced two perceptual similarity principles for synthesis quality assessment. Machine learning algorithms were used to predict the global and local quality scores of the synthesized texture, respectively. In this study, image processing techniques are used to extract the texture of Dongba paintings and synthesis different images. The line integral convolution algorithm is used to maintain the invariance of Dongba paintings during feature extraction. The improved Reinhard global color transfer algorithm is employed to transfer the international color of Dongba paintings and add local texture information. Finally, the generated image has an excellent visual expression effect.The remaining sections of the manuscript are ordered as follows. Section2 provides a detailed description of the proposed image synthesis process and illustrates the different techniques for image texture analysis. Section 3 illustrates the results of the proposed model, and Section 4 is about the conclusion.


## 2. Digital Image Synthesis Based on Dongba Painting Color Transmission

### 2.1. Vision Sensor Technology

To determine the existence, orientation, and accuracy of parts, vision sensors employ images acquired by a camera. These sensors are distinct from image inspection “systems” in which the camera, light, and controller are all combined into one unit, making setup and operation simple. The primary function of vision sensing technology is to collect visual information and then transmit this information to the required equipment. Vision sensors usually consist of one or more graphic sensors. These graphics sensors work together to ensure that the vision sensor completes its work. After obtaining the picture, the vision sensor compares the image with the specified requirements. Images that meet the requirements are saved. The image clarity of the vision sensor is measured in pixels [14].A complete set of vision sensors is equipped with more graphic sensors, light projectors, and necessary auxiliary equipment. After the image is acquired, the visual sensor compares and analyses it with the set image information requirements. Pictures that meet the specific requirements are retained. Vision sensors have the advantages of low cost and simple application. Therefore, it has a wide range of applications, including subinspection, detection, measurement, measurement, orientation, and other fields, which play a massive role in saving labor and improving work efficiency. Regardless of the industry, visual sensors have significantly dedicated human resources and improved work efficiency [15]. The working principle of optical sensing technology is shown in Figure 1.Figure 1
The working principle of the vision sensor.


### 2.2. Digital Image Synthesis Technology and Dongba Painting

Digital image synthesis technology mixes multiple original materials into a single composite picture. It combines all the source files or shots of images or animations into a structured and orderly production process. Meanwhile, it is also an essential factor in determining whether a photo or a cartoon can attract the audience’s attention and visual appeal [16]. Digital image synthesis technology is widely used in media, advertising, film, and television production. These applications seamlessly merge multiple images from different sources into one image. 3D visual effects include processing existing pictures and combining them into new ideas. The image source can be a rendered image used in the 3D processing, a photo directly taken by the camera, and so on. The two image elements are integrated into one embodiment so that there is no trace of processing [17]. This makes digital synthesis more complex. The principle of digital image synthesis technology is shown in Figure 2.Figure 2
The digital synthesis process of Dongba painting.Computer-generated imagery (CGI) is also a kind of digital image synthesis technology. It is a computer image technology widely used in movies, television, video games, interactive multimedia, and other fields. Whether a low-cost advertisement or a large-scale production film, the image elements are generated on the computer and then synthesized into a generalized background picture. In a broad sense, it includes standard lenses taken with film or digital cameras and can also be CGI pictures or digital street scenes [18]. The task of digital synthesis is to put different elements together and modify them to give them a photo-level realism [19–21]. Modern technology has produced incredible and realistic picture elements, such as the natural texture of hair, skin, clothing, fog, fireworks, and even fluids. The digital technology of nonlinear processing mode makes the pre- and post-processing work of film and television advertisements and publicity pictures easy and flexible. The manifestations of visual art are images and sounds. Painting is one of the most important ways of expression in film and television art. The traditional method of acquiring images is through camera photography, plus some specialized techniques such as model special effects, printing, and synthesis [22, 23]. Although there are many excellent works in the traditional film and television works, with the progress of science and technology and the passage of time, people's way of thinking and ideas have also undergone great changes. The traditional methods and means of film and television expression can no longer meet people’s requirements for visual art creation. Film and television image production involving digital technology can obtain lifelike images and simulate natural environments, which is a technical expressiveness that is difficult to achieve by traditional means, and greatly enriches the creation methods of film and television tables [24–27]. As the first batch of Dongba paintings to be listed as national intangible cultural heritage, the visual image of the God in the traditional Dongba scroll paintings of the Naxi ethnic group reflects the living conditions of the ancient society of the Naxi ethnic group. Dongba paintings are primarily composed of religious themes. The form and content are divided into wooden sign paintings, bamboo brush paintings, card paintings, and scroll paintings [24]. Dongba painting itself has extremely high artistic value, and its “form,” “meaning,” and “color” elements all have their meanings. The aspects of Dongba paintings are extracted and transformed by modern computer synthesis technology, which can generate a variety of artistic styles and achieve different visual effects.


### 2.3. Extraction of Dongba Painting Foreground Pattern Elements

To begin, the pattern of Dongba painting must be simulated while replicating its painting qualities. Algorithm simulation often causes image blur and large edge spacing, making the image distorted. The line drawing of Dongba painting is modeled and drawn and all saved in the elements library. The model is adjusted through the combination to complete the line drawing. The modeling process is shown in Figure3.Figure 3
Flow chart of Dongba painting modeling.In Figure3, the outline and details of the actual Dongba paintings are entirely preserved and express the primary information of the original image. The representative patterns in Dongba paintings are classified according to categories, such as hieroglyphic outlines, characteristic symbols, and animal and plant trunks. The pattern models of many Yunnan Dongba paintings are divided into character images, animal images, and other modules. Then, the Dongba painting line drawing is drawn through interactive editing and combination. The drawing process is shown in Figure 4.Figure 4
The drawing process of Dongba’s line drawing.The drawing methods of Dongba paintings are diverse. Dongba painting uses walls, wood chips, linen cloth, and Dongba paper as the drawing materials. These painting materials have different textures and rendering effects, uneven colors, and apparent noise-like texture effects [28]. Therefore, it is necessary to preprocess the line drawing before synthesis. The white picture is composed of different numbers of thick black curves to form the outline, which needs to be colored by simulating the hollow effect of the image outline [29]. The color assignment of the colored part can be pure black or other colors. The purpose of coloring is to thicken the system. This is the method of morphological processing in computer graphics. Under the principle of not changing the main body shape, the image contour can be colored, which solves the problem of thick silhouette and dark coloring in the digital synthesis process [30].The line integration convolution (LIC) algorithm can effectively maintain feature information and accurately reflect the direction of the vector. When convolving the texture, a texture image can generally be obtained if a white noise image is used directly. For example, if the direction of the vector field is all horizontal, the visualized image is similar to horizontal pencil sketch strokes. If the direction of the vector field forms a circle, the visualized image will resemble a vortex diagram. If an ordinary image is directly convolved, different streamline lengths will affect the appearance differently. Sometimes it is similar to the style of oil painting, and the final vision will be blurred as the length of the streamline increases. The principles of the LIC algorithm are shown in Figure5.Figure 5
The algorithm of LIC.The LIC alone cannot express the granularity of the vector field, so the multifrequency noise field is used for drawing and filling. High frequencies produce small vectors, and low frequencies produce large vectors. The generated high-frequency noise field isN1, and the calculation process is as follows:(1)Sx,y=rand0,100,Kx,y=rand10,20Tx,y≤n255Tx,yn,where Sx,y represents the random value and kx,y is the noise value of the pixel x,y . The a×a sizing template is used to perform mean filtering on N1, and other noise fields of different frequencies are generated. The weight distribution of the ith noise field of the k-th pixel x,y is calculated, as shown in the following:(2)Nx,yi=11+dx,yiN,where Nx,yi represents the distribution weight and dx,yi represents the distance between the k-th pixel kx,y and the center of the ith noise field pixel. According to the weight Nx,yi, it is estimated whether the pixel kx,y belongs to the noise field. Finally, the multifrequency noise field is obtained, as shown in the following:(3)1,Nx,yi=maxNx,yi,Nx,y2,…,Nx,y5,0,other,where 1 means it belongs to the noise field and 0 means it does not belong to the noise field. The obtained multifrequency noise field and vector field are processed by convolution and integration to generate the noise-like texture of Dongba painting.


### 2.4. Background Image Synthesis of Dongba Painting Using Texture Synthesis

Texture synthesis uses a small number of source texture samples to create a big texture pattern. Its goal is to eliminate seam aliasing in texture mapping [22, 23]. Texture synthesis is divided into process texture synthesis and using sample images. Process texture synthesis directly generates textures on the surface through the simulation of the physical generation process, such as hair, clouds, and wood grain, thereby avoiding the distortion caused by texture mapping. This method can obtain very realistic textures, but the parameters must be adjusted and tested repeatedly for each new consistency, which is not convenient enough. The texture synthesis using sample images uses small-area texture samples to stitch together to generate the entire surface’s texture according to the character’s geometry. It is similar and continuous in visual expression, neither requiring adjustment of parameters nor excessive time complexity. In texture rendering, it can save a lot of work and enhance the image’s optical performance.The image quilting algorithm is a texture synthesis algorithm based on block stitching. It can obtain a clear structure and regular arrangement of texture composite images. The process of the algorithm is shown in Figure6.Figure 6
Schematic diagram of the synthesis algorithm of image quilting texture.The algorithm randomly finds a picture area from the original image and marks it asP1 and puts it into the resulting image. Extract the next texture block P2 according to the scanning order. The error L of the overlapping area of P1 and P2 is calculated, as in the following:(4)L=∑i,j∈or1ij−r2ij2+g1ij−g2ij2+b1ij−b2ij2,where r1ij,g1ij, and b1ij represent the pixel value of the pixel point i,j in P1. r2ij,g2ij, and b2ij represent the pixel value of the pixel point i,j in P2. In the process of finding the optimal splicing line for two small blocks, there are three overlapping situations: vertical type, horizontal type, and L-shaped overlap area. There must be a path between overlapping areas with high similarity, which is the optimal suture line. To obtain the optimal stitching line, it is necessary first to calculate the square error u of each pixel in the overlapping area of P1 and P2, as shown in the following:(5)u=r1ij−r2ij2+g1ij−g2ij2+b1ij−b2ij2.The cumulative error of the best suture in the horizontal direction is shown in the following:(6)Ui,j=ui,j,j=1,ui,j+minUi−1,j−1,Ui,j−1,Ui+1,j−1,i>1.The cumulative error of the best suture in the vertical direction is shown in the following:(7)Ui,j=ui,j,i=1,ui,j+minUi−1,j−1,Ui−1,j,Ui−1,j+1,i>1.The calculation method of the L-shaped optimal suture thread is given in the following:(8)Ui,j=U¯i,j+U¯¯i,j,where U¯i,j represents the horizontal suture line and U¯¯i,j is the vertical suture line. All the texture tiles are calculated up to the end. It is not difficult to find that each corresponding pixel in the overlapping area of such a calculation method must be multiplied and added more than once. The calculation redundancy is inevitable. So, the image synthesis algorithm of quilting texture has been improved. The optimal texture block search method is changed to an “r” type overlapping area, and the error is performed. When looking for the best horizontal stitching line, the scope is expanded to find a whole row of textures. Next, the two rows of surfaces are stitched together, reducing the amount of error calculation in the overlapping area and removing redundant parts.In this study, Visual C++2018 is used to conduct many experiments on the improved texture synthesis algorithm, and the performance is compared with the classic synthesis algorithm of image quilting texture. The hardware environment is configured as CPU: Intel Core i5-480M (2.66 GHz); 2 GB memory capacity and graphics card used are Nvidia Geforce GT 425M. The list of texture samples and parameters used is shown in Table1.Table 1
Texture sample.
Texture sample numberSampleSample sizeSample name164∗ 64Green264∗ 64Newspaper3104∗ 104Peanut4256∗ 256Cherry5128∗ 128SandIn the digital image synthesis of Dongba painting, if different background images can be added, the sample subject matter can be generated into a wide variety of Dongba painting digital composite works. The Dongba painting with a single background texture can be synthesized directly based on texture synthesis. For the processing of background textures with rich colors and complex patterns, image software such as Photoshop is selected for image stitching. Different ways of fusion between the background and foreground images can generate different kinds of digitally synthesized Dongba painting works.


### 2.5. Local Color Transfer Algorithm of Dongba Painting Using Color Transfer Rights

Color transfer is offered as a way to preserve the tone and layering of actual Dongba paintings in digitally created analog Dongba paintings as much as feasible. Color transfer includes local color transfer and global color transfer to enhance the visual effect of the synthesized Dongba painting. The RGB color space is a commonly used color display model. In the three-dimensional space, R, G, and B represent the three coordinate axes of red, green, and blue, respectively. The values of these three components determine the color of each pixel. Lab color space is a color system using visual design. L stands for brightness, yellow, and blue channels, and b stands for red and green channels. There is no correlation between the three channels.The Reinhard global color transfer algorithm adjusts the average value and standard deviation to give the two images a certain degree of visual similarity. Since the Reinhard algorithm has excellent color and composition differences, the image conversion effect is not ideal. It is optimized. Because Reinhard’s algorithm transfers general color information, little consideration is given to the correlation between pixels in small areas of local images. Ignoring the local texture features of the image will cause different degrees of image distortion. Therefore, the local texture information of the picture is added since the overall color tone shifts so that the result can retain the critical data of both the image color and texture.In this study, the local standard deviation of the image is calculated using a template with a size ofm×n and then the local source image feature vector is expressed as μs1∗,μsa∗,μsb∗,σs1∗,σsa∗,andσsb∗ The mean value method of the local reference image is defined as μd1∗,μda∗,μdb∗,σd1∗,σda∗,andσdb∗ The improved Reinhard local color transfer algorithm is given in the following:(9)1∗=c1σd1σs1+c2σd1∗σs1∗1s−μs1+μd1,a∗=c1σda∗σsa+C2σda∗|σsa∗as−μsa+μd|a,b∗=c1σdbσsb+c2σdb∗σsb∗bs−μdb,where c1≥0,c2≥0, and then(10)c1+c2=1.Through the adjustment of thec1 and c2 parameters, the source image not only retains key global color information but also has local texture information. Partial color transfer can realize the selection of a specific area for color transfer while the colors of other sites remain unchanged. The proposed local color transfer algorithm first selects the place to be transferred in the source and target images using interactive segmentation. It constructs the color transfer weight coefficient for the source image. According to the size of the color transfer weight coefficient, the degree of influence of the source image by the color transfer of the target image is determined, and the partial color transfer is finally realized. The flow of the algorithm is shown in Figure 7.Figure 7
Flow chart of the local color transfer algorithm using color transfer rights.


## 2.1. Vision Sensor Technology

To determine the existence, orientation, and accuracy of parts, vision sensors employ images acquired by a camera. These sensors are distinct from image inspection “systems” in which the camera, light, and controller are all combined into one unit, making setup and operation simple. The primary function of vision sensing technology is to collect visual information and then transmit this information to the required equipment. Vision sensors usually consist of one or more graphic sensors. These graphics sensors work together to ensure that the vision sensor completes its work. After obtaining the picture, the vision sensor compares the image with the specified requirements. Images that meet the requirements are saved. The image clarity of the vision sensor is measured in pixels [14].A complete set of vision sensors is equipped with more graphic sensors, light projectors, and necessary auxiliary equipment. After the image is acquired, the visual sensor compares and analyses it with the set image information requirements. Pictures that meet the specific requirements are retained. Vision sensors have the advantages of low cost and simple application. Therefore, it has a wide range of applications, including subinspection, detection, measurement, measurement, orientation, and other fields, which play a massive role in saving labor and improving work efficiency. Regardless of the industry, visual sensors have significantly dedicated human resources and improved work efficiency [15]. The working principle of optical sensing technology is shown in Figure 1.Figure 1
The working principle of the vision sensor.


## 2.2. Digital Image Synthesis Technology and Dongba Painting

Digital image synthesis technology mixes multiple original materials into a single composite picture. It combines all the source files or shots of images or animations into a structured and orderly production process. Meanwhile, it is also an essential factor in determining whether a photo or a cartoon can attract the audience’s attention and visual appeal [16]. Digital image synthesis technology is widely used in media, advertising, film, and television production. These applications seamlessly merge multiple images from different sources into one image. 3D visual effects include processing existing pictures and combining them into new ideas. The image source can be a rendered image used in the 3D processing, a photo directly taken by the camera, and so on. The two image elements are integrated into one embodiment so that there is no trace of processing [17]. This makes digital synthesis more complex. The principle of digital image synthesis technology is shown in Figure 2.Figure 2
The digital synthesis process of Dongba painting.Computer-generated imagery (CGI) is also a kind of digital image synthesis technology. It is a computer image technology widely used in movies, television, video games, interactive multimedia, and other fields. Whether a low-cost advertisement or a large-scale production film, the image elements are generated on the computer and then synthesized into a generalized background picture. In a broad sense, it includes standard lenses taken with film or digital cameras and can also be CGI pictures or digital street scenes [18]. The task of digital synthesis is to put different elements together and modify them to give them a photo-level realism [19–21]. Modern technology has produced incredible and realistic picture elements, such as the natural texture of hair, skin, clothing, fog, fireworks, and even fluids. The digital technology of nonlinear processing mode makes the pre- and post-processing work of film and television advertisements and publicity pictures easy and flexible. The manifestations of visual art are images and sounds. Painting is one of the most important ways of expression in film and television art. The traditional method of acquiring images is through camera photography, plus some specialized techniques such as model special effects, printing, and synthesis [22, 23]. Although there are many excellent works in the traditional film and television works, with the progress of science and technology and the passage of time, people's way of thinking and ideas have also undergone great changes. The traditional methods and means of film and television expression can no longer meet people’s requirements for visual art creation. Film and television image production involving digital technology can obtain lifelike images and simulate natural environments, which is a technical expressiveness that is difficult to achieve by traditional means, and greatly enriches the creation methods of film and television tables [24–27]. As the first batch of Dongba paintings to be listed as national intangible cultural heritage, the visual image of the God in the traditional Dongba scroll paintings of the Naxi ethnic group reflects the living conditions of the ancient society of the Naxi ethnic group. Dongba paintings are primarily composed of religious themes. The form and content are divided into wooden sign paintings, bamboo brush paintings, card paintings, and scroll paintings [24]. Dongba painting itself has extremely high artistic value, and its “form,” “meaning,” and “color” elements all have their meanings. The aspects of Dongba paintings are extracted and transformed by modern computer synthesis technology, which can generate a variety of artistic styles and achieve different visual effects.


## 2.3. Extraction of Dongba Painting Foreground Pattern Elements

To begin, the pattern of Dongba painting must be simulated while replicating its painting qualities. Algorithm simulation often causes image blur and large edge spacing, making the image distorted. The line drawing of Dongba painting is modeled and drawn and all saved in the elements library. The model is adjusted through the combination to complete the line drawing. The modeling process is shown in Figure3.Figure 3
Flow chart of Dongba painting modeling.In Figure3, the outline and details of the actual Dongba paintings are entirely preserved and express the primary information of the original image. The representative patterns in Dongba paintings are classified according to categories, such as hieroglyphic outlines, characteristic symbols, and animal and plant trunks. The pattern models of many Yunnan Dongba paintings are divided into character images, animal images, and other modules. Then, the Dongba painting line drawing is drawn through interactive editing and combination. The drawing process is shown in Figure 4.Figure 4
The drawing process of Dongba’s line drawing.The drawing methods of Dongba paintings are diverse. Dongba painting uses walls, wood chips, linen cloth, and Dongba paper as the drawing materials. These painting materials have different textures and rendering effects, uneven colors, and apparent noise-like texture effects [28]. Therefore, it is necessary to preprocess the line drawing before synthesis. The white picture is composed of different numbers of thick black curves to form the outline, which needs to be colored by simulating the hollow effect of the image outline [29]. The color assignment of the colored part can be pure black or other colors. The purpose of coloring is to thicken the system. This is the method of morphological processing in computer graphics. Under the principle of not changing the main body shape, the image contour can be colored, which solves the problem of thick silhouette and dark coloring in the digital synthesis process [30].The line integration convolution (LIC) algorithm can effectively maintain feature information and accurately reflect the direction of the vector. When convolving the texture, a texture image can generally be obtained if a white noise image is used directly. For example, if the direction of the vector field is all horizontal, the visualized image is similar to horizontal pencil sketch strokes. If the direction of the vector field forms a circle, the visualized image will resemble a vortex diagram. If an ordinary image is directly convolved, different streamline lengths will affect the appearance differently. Sometimes it is similar to the style of oil painting, and the final vision will be blurred as the length of the streamline increases. The principles of the LIC algorithm are shown in Figure5.Figure 5
The algorithm of LIC.The LIC alone cannot express the granularity of the vector field, so the multifrequency noise field is used for drawing and filling. High frequencies produce small vectors, and low frequencies produce large vectors. The generated high-frequency noise field isN1, and the calculation process is as follows:(1)Sx,y=rand0,100,Kx,y=rand10,20Tx,y≤n255Tx,yn,where Sx,y represents the random value and kx,y is the noise value of the pixel x,y . The a×a sizing template is used to perform mean filtering on N1, and other noise fields of different frequencies are generated. The weight distribution of the ith noise field of the k-th pixel x,y is calculated, as shown in the following:(2)Nx,yi=11+dx,yiN,where Nx,yi represents the distribution weight and dx,yi represents the distance between the k-th pixel kx,y and the center of the ith noise field pixel. According to the weight Nx,yi, it is estimated whether the pixel kx,y belongs to the noise field. Finally, the multifrequency noise field is obtained, as shown in the following:(3)1,Nx,yi=maxNx,yi,Nx,y2,…,Nx,y5,0,other,where 1 means it belongs to the noise field and 0 means it does not belong to the noise field. The obtained multifrequency noise field and vector field are processed by convolution and integration to generate the noise-like texture of Dongba painting.


## 2.4. Background Image Synthesis of Dongba Painting Using Texture Synthesis

Texture synthesis uses a small number of source texture samples to create a big texture pattern. Its goal is to eliminate seam aliasing in texture mapping [22, 23]. Texture synthesis is divided into process texture synthesis and using sample images. Process texture synthesis directly generates textures on the surface through the simulation of the physical generation process, such as hair, clouds, and wood grain, thereby avoiding the distortion caused by texture mapping. This method can obtain very realistic textures, but the parameters must be adjusted and tested repeatedly for each new consistency, which is not convenient enough. The texture synthesis using sample images uses small-area texture samples to stitch together to generate the entire surface’s texture according to the character’s geometry. It is similar and continuous in visual expression, neither requiring adjustment of parameters nor excessive time complexity. In texture rendering, it can save a lot of work and enhance the image’s optical performance.The image quilting algorithm is a texture synthesis algorithm based on block stitching. It can obtain a clear structure and regular arrangement of texture composite images. The process of the algorithm is shown in Figure6.Figure 6
Schematic diagram of the synthesis algorithm of image quilting texture.The algorithm randomly finds a picture area from the original image and marks it asP1 and puts it into the resulting image. Extract the next texture block P2 according to the scanning order. The error L of the overlapping area of P1 and P2 is calculated, as in the following:(4)L=∑i,j∈or1ij−r2ij2+g1ij−g2ij2+b1ij−b2ij2,where r1ij,g1ij, and b1ij represent the pixel value of the pixel point i,j in P1. r2ij,g2ij, and b2ij represent the pixel value of the pixel point i,j in P2. In the process of finding the optimal splicing line for two small blocks, there are three overlapping situations: vertical type, horizontal type, and L-shaped overlap area. There must be a path between overlapping areas with high similarity, which is the optimal suture line. To obtain the optimal stitching line, it is necessary first to calculate the square error u of each pixel in the overlapping area of P1 and P2, as shown in the following:(5)u=r1ij−r2ij2+g1ij−g2ij2+b1ij−b2ij2.The cumulative error of the best suture in the horizontal direction is shown in the following:(6)Ui,j=ui,j,j=1,ui,j+minUi−1,j−1,Ui,j−1,Ui+1,j−1,i>1.The cumulative error of the best suture in the vertical direction is shown in the following:(7)Ui,j=ui,j,i=1,ui,j+minUi−1,j−1,Ui−1,j,Ui−1,j+1,i>1.The calculation method of the L-shaped optimal suture thread is given in the following:(8)Ui,j=U¯i,j+U¯¯i,j,where U¯i,j represents the horizontal suture line and U¯¯i,j is the vertical suture line. All the texture tiles are calculated up to the end. It is not difficult to find that each corresponding pixel in the overlapping area of such a calculation method must be multiplied and added more than once. The calculation redundancy is inevitable. So, the image synthesis algorithm of quilting texture has been improved. The optimal texture block search method is changed to an “r” type overlapping area, and the error is performed. When looking for the best horizontal stitching line, the scope is expanded to find a whole row of textures. Next, the two rows of surfaces are stitched together, reducing the amount of error calculation in the overlapping area and removing redundant parts.In this study, Visual C++2018 is used to conduct many experiments on the improved texture synthesis algorithm, and the performance is compared with the classic synthesis algorithm of image quilting texture. The hardware environment is configured as CPU: Intel Core i5-480M (2.66 GHz); 2 GB memory capacity and graphics card used are Nvidia Geforce GT 425M. The list of texture samples and parameters used is shown in Table1.Table 1
Texture sample.
Texture sample numberSampleSample sizeSample name164∗ 64Green264∗ 64Newspaper3104∗ 104Peanut4256∗ 256Cherry5128∗ 128SandIn the digital image synthesis of Dongba painting, if different background images can be added, the sample subject matter can be generated into a wide variety of Dongba painting digital composite works. The Dongba painting with a single background texture can be synthesized directly based on texture synthesis. For the processing of background textures with rich colors and complex patterns, image software such as Photoshop is selected for image stitching. Different ways of fusion between the background and foreground images can generate different kinds of digitally synthesized Dongba painting works.


## 2.5. Local Color Transfer Algorithm of Dongba Painting Using Color Transfer Rights

Color transfer is offered as a way to preserve the tone and layering of actual Dongba paintings in digitally created analog Dongba paintings as much as feasible. Color transfer includes local color transfer and global color transfer to enhance the visual effect of the synthesized Dongba painting. The RGB color space is a commonly used color display model. In the three-dimensional space, R, G, and B represent the three coordinate axes of red, green, and blue, respectively. The values of these three components determine the color of each pixel. Lab color space is a color system using visual design. L stands for brightness, yellow, and blue channels, and b stands for red and green channels. There is no correlation between the three channels.The Reinhard global color transfer algorithm adjusts the average value and standard deviation to give the two images a certain degree of visual similarity. Since the Reinhard algorithm has excellent color and composition differences, the image conversion effect is not ideal. It is optimized. Because Reinhard’s algorithm transfers general color information, little consideration is given to the correlation between pixels in small areas of local images. Ignoring the local texture features of the image will cause different degrees of image distortion. Therefore, the local texture information of the picture is added since the overall color tone shifts so that the result can retain the critical data of both the image color and texture.In this study, the local standard deviation of the image is calculated using a template with a size ofm×n and then the local source image feature vector is expressed as μs1∗,μsa∗,μsb∗,σs1∗,σsa∗,andσsb∗ The mean value method of the local reference image is defined as μd1∗,μda∗,μdb∗,σd1∗,σda∗,andσdb∗ The improved Reinhard local color transfer algorithm is given in the following:(9)1∗=c1σd1σs1+c2σd1∗σs1∗1s−μs1+μd1,a∗=c1σda∗σsa+C2σda∗|σsa∗as−μsa+μd|a,b∗=c1σdbσsb+c2σdb∗σsb∗bs−μdb,where c1≥0,c2≥0, and then(10)c1+c2=1.Through the adjustment of thec1 and c2 parameters, the source image not only retains key global color information but also has local texture information. Partial color transfer can realize the selection of a specific area for color transfer while the colors of other sites remain unchanged. The proposed local color transfer algorithm first selects the place to be transferred in the source and target images using interactive segmentation. It constructs the color transfer weight coefficient for the source image. According to the size of the color transfer weight coefficient, the degree of influence of the source image by the color transfer of the target image is determined, and the partial color transfer is finally realized. The flow of the algorithm is shown in Figure 7.Figure 7
Flow chart of the local color transfer algorithm using color transfer rights.


## 3. Results

### 3.1. Comparison of Synthesis Results of Different Texture Generation Methods

Texture analysis is of paramount importance in public art design. We compared the synthesis effect of 5 texture sample images of various sizes. Table2 shows the basic synthesis effects and optimized synthesis effect of the image quilting texture algorithm. The optimized synthesis algorithm of image quilting texture can achieve the same texture synthesis effect as the original image quilting algorithm, which can meet the actual requirements. Under the premise of the same synthesis effect, we compared the proposed texture synthesis algorithm with the texture synthesis algorithms presented in references [12, 13], respectively. The comparative results are shown in Figure 8. It is evident that the optimized synthesis algorithm of image quilting texture has faster synthesis speed and shorter synthesis time. Regardless of random texture or structural texture, the overall synthesis efficiency has been improved. To a large extent, the time performance of the original algorithm has been optimized. For the same surface, the synthesis time is reduced by the cherry texture, which is facilitated by 87.67%.Table 2
Texture sample.
Texture sample numberOriginal texture sampleThe synthesis effect of the synthesis algorithm of image quilting textureOptimized synthesis effect of the synthesis algorithm of image quilting texture12345Figure 8
Comparison of synthesis speed of different texture synthesis algorithms.The result of the digital composite image after the fusion of the foreground and background of the Dongba painting is compared with the real Dongba painting works, and the results are shown in Figure9.Figure 9
Comparison between the digitally synthesized Dongba painting and the actual Dongba painting: (a) Digital synthesis Dongba painting. (b) Real Dongba painting.
(a)(b)In Figure9, the simulated and synthesized Dongba paintings have bright colors and smooth lines, which show the artistic sense of Dongba paintings. The foreground and background are processed separately and then digitally synthesized, which dramatically expands the subject range of Dongba paintings and produces a different visual effect. In the portrayal of figures, it has distinct noise-like texture features and the colors are similar to actual Dongba paintings.


### 3.2. Color Transfer Simulation Effects

We performed a different simulation to generate color transfer effects. By controlling different parameters, the image processing results are obtained, as shown in Figure10.Figure 10
Comparison of image processing results obtained by differentc1c2 parameters. (a) C1 = 0.2 and C2 = 0.8; (b) C1 = 0.5 and C2 = 0.5; (c) C1 = 0.6 and C2 = 0.4; (d) C1 = 0.8 and C2 = 0.2.
(a)(b)(c)(d)In Figure10, after the local texture information is increased, the distortion of the image is reduced, and the color contrast is reduced. The larger the parameter value c2, the more local texture information. Control c2 is used to adjust the overall visual effect of the global color transmission.


### 3.3. Performance Comparison of Local Color Transfer Algorithms

We employed different evaluation metrics to assess the performance of the local color transfer algorithms. The proposed local color transmission algorithm is compared in terms of Accuracy, Precision, Recall, and F1 values of other similar algorithms in references [28, 29]. The result is shown in Figure 11.Figure 11
Comparison of image processing performance of different color transmission algorithms.In Figure11, the image recognition accuracy of the proposed local color transfer algorithm reaches 88.9%. Compared with other algorithms, the prediction accuracy rate is improved by at least 6.4%. Meanwhile, the algorithm’s Precision, Recall, and F1 values are also the highest, with a difference of at least 2.6%. As compared with other local color transmission algorithms, the proposed color transmission algorithm has better performance and higher recognition accuracy.The proposed background image synthesis method based on texture synthesis has better performance than other algorithms. In addition, the improved Reinhard local color transfer algorithm is also better than different algorithms for enhancing digitally synthesized images. The image synthesis method based on digital image synthesis technology and visual sensing technology is helpful to the visual communication of public art paintings.


## 3.1. Comparison of Synthesis Results of Different Texture Generation Methods

Texture analysis is of paramount importance in public art design. We compared the synthesis effect of 5 texture sample images of various sizes. Table2 shows the basic synthesis effects and optimized synthesis effect of the image quilting texture algorithm. The optimized synthesis algorithm of image quilting texture can achieve the same texture synthesis effect as the original image quilting algorithm, which can meet the actual requirements. Under the premise of the same synthesis effect, we compared the proposed texture synthesis algorithm with the texture synthesis algorithms presented in references [12, 13], respectively. The comparative results are shown in Figure 8. It is evident that the optimized synthesis algorithm of image quilting texture has faster synthesis speed and shorter synthesis time. Regardless of random texture or structural texture, the overall synthesis efficiency has been improved. To a large extent, the time performance of the original algorithm has been optimized. For the same surface, the synthesis time is reduced by the cherry texture, which is facilitated by 87.67%.Table 2
Texture sample.
Texture sample numberOriginal texture sampleThe synthesis effect of the synthesis algorithm of image quilting textureOptimized synthesis effect of the synthesis algorithm of image quilting texture12345Figure 8
Comparison of synthesis speed of different texture synthesis algorithms.The result of the digital composite image after the fusion of the foreground and background of the Dongba painting is compared with the real Dongba painting works, and the results are shown in Figure9.Figure 9
Comparison between the digitally synthesized Dongba painting and the actual Dongba painting: (a) Digital synthesis Dongba painting. (b) Real Dongba painting.
(a)(b)In Figure9, the simulated and synthesized Dongba paintings have bright colors and smooth lines, which show the artistic sense of Dongba paintings. The foreground and background are processed separately and then digitally synthesized, which dramatically expands the subject range of Dongba paintings and produces a different visual effect. In the portrayal of figures, it has distinct noise-like texture features and the colors are similar to actual Dongba paintings.


## 3.2. Color Transfer Simulation Effects

We performed a different simulation to generate color transfer effects. By controlling different parameters, the image processing results are obtained, as shown in Figure10.Figure 10
Comparison of image processing results obtained by differentc1c2 parameters. (a) C1 = 0.2 and C2 = 0.8; (b) C1 = 0.5 and C2 = 0.5; (c) C1 = 0.6 and C2 = 0.4; (d) C1 = 0.8 and C2 = 0.2.
(a)(b)(c)(d)In Figure10, after the local texture information is increased, the distortion of the image is reduced, and the color contrast is reduced. The larger the parameter value c2, the more local texture information. Control c2 is used to adjust the overall visual effect of the global color transmission.


## 3.3. Performance Comparison of Local Color Transfer Algorithms

We employed different evaluation metrics to assess the performance of the local color transfer algorithms. The proposed local color transmission algorithm is compared in terms of Accuracy, Precision, Recall, and F1 values of other similar algorithms in references [28, 29]. The result is shown in Figure 11.Figure 11
Comparison of image processing performance of different color transmission algorithms.In Figure11, the image recognition accuracy of the proposed local color transfer algorithm reaches 88.9%. Compared with other algorithms, the prediction accuracy rate is improved by at least 6.4%. Meanwhile, the algorithm’s Precision, Recall, and F1 values are also the highest, with a difference of at least 2.6%. As compared with other local color transmission algorithms, the proposed color transmission algorithm has better performance and higher recognition accuracy.The proposed background image synthesis method based on texture synthesis has better performance than other algorithms. In addition, the improved Reinhard local color transfer algorithm is also better than different algorithms for enhancing digitally synthesized images. The image synthesis method based on digital image synthesis technology and visual sensing technology is helpful to the visual communication of public art paintings.


## 4. Conclusion

The application of digital image synthesis is becoming more and more widespread as computer image processing technology advances. In this study, digital image synthesis technology was applied to the foreground and background images of Dongba paintings. The recombination of background and foreground elements shows a different visual art. The foreground elements and background elements of Dongba paintings are extracted and processed separately and merged using the digital synthesis method of interactive white drawing and coloring. This process enabled the recoloring of the line drawing. The background image synthesis method based on texture synthesis was applied, and several Dongba painting background patterns were generated. Furthermore, an improved Reinhard local color transfer algorithm is proposed. The digitally synthesized image of Dongba art is enhanced, and the performance of the generated image is significantly better. Our results show that the proposed method performs better than the other image synthesis methods. However, in some of the proposed methods, the texture element library material is less established. The material library will be further expanded in the future, with more choices for image synthesis established. In addition, when the actual Dongba paintings are fused, the image will appear to be over-fused with vivid color elements. Noise will be added during the simulation process to achieve better visual effects.



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*Source: 6480172-2022-11-18.xml*