Digital Jacquard Textile Design In A Colorless Mode

Transcription

1 Digital Jacquard Textile Design In A Colorless Mode NG, Frankie M.C. and ZHOU, Jiu Institute of Textiles and Clothing, The Hong Kong Polytechnic University, Hong Kong. ABSTRACT Jacquard fabric is regarded as a high-grade textile, having intricate, interesting color and texture, and digital image design is the latest technique of computer art in the design field. Merging the design features of jacquard fabrics and digital image, this study was carried out to investigate digital jacquard fabric design in a colorless mode, which is one of the main modes of digital image design; another is that of a colorful mode. In this paper, the design principles and design methods for unconventional digital jacquard fabric design in a colorless mode were analyzed critically based on the application of digital technologies, and in particular, the digital color theory so that with tailor-made structural design, any colorless digital images with certain grays can be designed to form jacquard fabrics directly. The results of this study bring about an innovative design concept in jacquard fabrics and have a significant influence on the future development of jacquard textiles. Keywords: digital; jacquard; colorless mode; black-and-white fabric; shadow weaves 1. Introduction Jacquard fabric is one kind of woven textiles. It has always been regarded as a high-grade textile characterized by intricate, detailed, woven-in motifs. Any jacquard textiles from the most fragile (silk brocades) to the most rugged (tapestries) are noted for their beautiful design motifs and colors. However, jacquard textile design is difficult to produce due to the dual nature of technology and art in the course of production. There are many unmeasured factors during the processes of jacquard textile design attributed to the success of the production of these intricate fabrics. Currently, the advancement and application of digital technologies play an important role in the field of jacquard textile design. Jacquard weaving is a traditional technology with a long history. Before 1804 when Joseph Jacquard developed punch cards to operate the Jacquard machine, the production of jacquard textiles was controlled by hand. The original loom was first called a treadle loom, later as pattern loom and finally a draw loom. Now, Jacquard machine has developed into an electronic form with computer controlling, and Net communication is widely used in jacquard weaving sheds. Meanwhile, the number of hooks used in the electronic Jacquard machine has 36 increased to 20,000 (Weinsdorfer, 2004), with the patterning scope increased substantially too. The application of the Computer Aided Design system (CAD) in jacquard textiles began in 1979 (Lee, 2000). The CAD system of jacquard weaving developed rapidly as a result of the advances in computer technology. In just 20 years, Jacquard Textile CAD System developed from one of small random access memory (RAM) operated at low speed to a large RAM capacity at high speed. It is envisaged that computers may one day replace designers in textile design. Obviously, the advancement of CAD in jacquard textiles is changing the trends of jacquard textile design, which offers a brand new design concept of jacquard textile design and lays a foundation for designing jacquard fabrics in a digital mode. It is well known that the theory of computer operation is one that is based on the binary system, which was originally developed from the punch card of the jacquard loom when computerization was first applied in 1946 (Lee, 2000). Today the digital technologies based on the binary system has great influence on jacquard textile design, and plays an important role in the field of digital image design at large. The new concept of jacquard textile design incorporating digital technology is proposed as digital jacquard textile design. Research in the field of digital

2 jacquard textile design can broadly be divided into two parts: colorless mode and colorful mode. In this paper, an in-depth analysis of the principles and methods of digital jacquard textile design in the colorless mode is reported. 2. Design Principles 2.1 The Features of Digital Jacquard Textile Design in the Colorless Mode Digital textile is a new term borrowed from computing science. Digital jacquard textile design refers to the process whereby jacquard textiles are designed by means of the Computer-Aided-Design system. In computer image design, there are two formats of image files that can be used: bitmap and vectorgraph. Only bitmap image matches the requirements of textile design. The bitmap images can further be classified into colorless images and colorful images. In this study, the colorless images were employed to develop the textile products, and they serve as foundation in the research of digital jacquard design. In order to acquire a thorough understanding of the nature of jacquard fabrics designed in the colorless mode, it is necessary to investigate the inherent characteristics of jacquard fabrics. Jacquard fabric is one kind of woven fabrics that is produced by means of interlacing the warp and weft threads. When the fabric is mainly interwoven by one series of warp and one series of weft, it is called single layer fabric (Grosicki, 1975). Pattern design for single layer fabrics is often done on a monochrome similar to designing digital colorless images using the computer system. Therefore, single layer jacquard textile design in a colorless mode done via the deployment of digitalization is regarded as an innovative means by which a different type of single layer fabrics differs from the traditional ones is developed. In short, there are two distinctive features in the design of digital colorless jacquard textiles: 1) structural design that is developed directly from colorless mode digital image, and 2) whose products consist of one series of warp and one series of weft threads for interlacing (Grosicki, 1975). As a result, digital jacquard fabrics designed in a colorless mode are capable of expressing the finer details as a black-and-white photograph. For distinguishing from traditional single layer fabric, this new type of single layer fabric developed in a digital colorless way is also called black-and-white fabric. 2.2 Design Principles of Digital Jacquard Textile Design in the Colorless Mode The prominent characteristic of the black-and-white fabrics is that it creates a new artistic style of jacquard fabric by merging the digital colorless images and weaving structure seamlessly with the aid of computing technology. The key of the design principles lies in pattern design and weave design Design Principle of Pattern Design Conventional jacquard textile design involved pattern design, weave design and craft design (point paper design) (Grosicki, 1975), all of which are manual processes. Pattern design is limited by weave design and craft design. Normally, textile designers perform their design work by experience gained from past trial-and-error practices. In fact, jacquard fabric design has always been considered as highly complex due to the many unpredicted factors during its design processes, and pattern design needs longer time to conceive, design and trials. Thanks to the widespread application of digital technologies which has offered more opportunities to innovate jacquard fabric design. The pattern design of black-and-white fabrics can now be achieved by using the CAD system and by such means, the pattern effect is finer than that of traditional hand-drawn fabrics design. In addition, the number of colors applied to pattern design will reach one hundred or above which is a few times more than that of the traditional fabrics. By the fact that human eyes can distinguish a maximum of 64 grade grays in a monochromatic image (Zhou, 2002), the 37

3 grayscale of digital image should be equal or more than this number if the design wants to imitate a true-color effect of colorless jacquard fabrics. In computer image design, the grayscale of the colorless image is presented in terms of bit length. For example, an 8-bit shows 256 grade grays and a 6-bit grayscale shows 64 grade grays. The relationship between the bit length and gray grades is indicated in Table 1. The pattern design in the colorless mode of digital jacquard fabrics should content with the requirement of gray grades. Table 1. The relation between the bit-length and gray grades Bit-length 1-bit 2-bit 3-bit 4-bit 5-bit 6-bit 7-bit 8-bit Gray grades Design Principle of Weave Design Weave design is one of the most important steps during the jacquard textile design processes. It enables the creation of a fabric structure that matches the original design concept. The weave design of black-and-white fabrics should be approached with a pattern of more than 64 gray grades. Same as the pattern design, weave design is created entirely by means of the computer system both in designing and editing. Among the many weaving structures, shadow weaves are the most suitable for the structural design of black-and-white fabrics, for it reveals the fine details on the surface of figured fabrics. Shadow weaves can be designed from simple weaves, such as twill and satin. The latter is ideal in designing black-and-white fabrics to achieve a flat and smooth structure. Figure 1 shows the design method of satin shadow weaves, of which the weave repeat is 8 8. There are three directions that can be utilized to form shadow weaves through the addition of interlacing points: warp-wise, weft-wise and diagonal (Zhou, 2002), each of them displays 7 gray grades. The calculation formula is N-1, where N indicates the weave repeat. Among them, the diagonal transition has relatively limited applications owing to the lack of stability in its weaving structure; the warp-wise transition better suits for expression in fabrics of which the warp density is more than the weft density while weft-wise transition better suits the other way round. Fig. 1. The principle of satin shadow weave design The gray grades may be extended by means of enlarging the weave repeat or using variational shadow weaves. However, in terms of universality of weaves, and since the number of hooks needs to be a multiple of the weave repeat, the effective weave repeats are mostly 8, 12, 16, 24, 36, 48 and 60. Table 2 indicates the relationship between the weave repeat and gray grades. The calculation formula for minimum gray grades in which the gap is N floats between each weave is N-1, and 38

4 the calculation formula for maximum gray grades in which the gap is one float between each weave is [N*(N-2)+1], where N indicates the weave repeat. Table 2. The relationship between the weave repeat and gray grades Weave repeat size Gray grades (min.) Gray grades (max.) According to the data shown in Table 1 and 2, different ways can be integrated to design a shadow weave whose gray grades equal to those of the corresponding woven pattern (see Figure 1). Figure 2 shows the design sample of satin shadow weaves having 64 gray grades to match the 6-bit grayscale woven pattern. Fig. 2. Shadow weaves design for the 64 gray grades (6-bit) pattern Using a Jacquard Textile CAD System to design satin shadow weaves has the benefit of identifying potential mistakes and correcting them in advance of production. Black-and-white fabrics designed in a colorless mode puts emphasis on fine texture and details similar to a black-and-white photograph. To this end, finer threads and high density weaves are necessary. The referenced specification for fabric design is shown in Table 3 (Zhou, 2002). Table 3. Essential specification of black-and-white fabrics Yarn Warp: 22.2/24.4dtex silk 2 Weft: 22.2/24.4dtex silk 3 Density Warp: 1150 yarns/10cm Weft: 800 yarns/10cm Composition Silk 100% Weight 144 g/m 2 Weave Shadow weaves The parameters of the black-and-white fabrics shown in Table 3 are devised to match the technology condition of a silk weaving mill. In mass production, the parameters could be adjusted quickly to address the requirements of a given customer using the Jacquard Textile CAD System and electronic Jacquard machine with all the design data saved in a digital format. 39

5 3. Design Method For the design and production of black-and-white fabrics designed in the colorless mode using the jacquard textile design CAD system and electronic jacquard machine, the work route can be described as follows (see Figure 3). Generally, during weaving production, an advanced weaving loom, such as rapier loom, can be used together with an electronic Jacquard machine. Fig. 3. Work route of designing and producing black-and-white fabrics 3.1 Design Processes Black-and-white fabric is designed in a single layer structure, i.e., the fabric is interlaced by one series of warp and one series of weft threads so that the design of the fabric structure is correspondingly regular. The major design input during this process is the pattern and weave design in the Jacquard Textile CAD System. The series of tasks carried out is presented in Figure 4: Fig. 4. Design processes for black-and-white fabrics In the course of design, the first step is pattern design. It involves hand-drawn artwork and/or photographic images. The pattern is then scanned and saved in the format of an image file. According only to the weaving parameters of fabrics, the computer image is then revised by using the edit tools offering in the Jacquard Textile CAD System, forming a craft image with limited gray grades and smooth edges. Finally, the weaves designs that meet the requirements of the production of fabrics are built and edited in the computer, and are further applied to replace each of the gray in the colorless image under a fixed start point. As a result, the output one is a weaving pattern being composed of weaving data (see Figure 5), i.e. lifting or lowering only two information in each warp. It provides the foundation for further simulation of black-and-white fabrics. 40

6 Fig. 5. Weaving pattern of black-and-white fabrics Besides, since the colors in a black-and-white fabric are translated by changing either the warp thread or the weft, the black-and-white fabrics designed by using digital jacquard technique can therefore be used to develop a series of products with the same weaving pattern, but showing different color effects. 3.2 Production Processes Black-and-white fabrics must be produced on electronic Jacquard machines. It is different from traditional mechanical Jacquard being controlled by punched paper. The production processes of black-and-white fabrics are shown in Figure 6. Fig. 6. Production processes of black-and-white fabrics During the production processes shown above, one of the most important tasks was to transform the weaving pattern into weaving data, which could be read by a computer controller of electronic Jacquard. Different Jacquard machines use different formats of weaving data. Therefore, it was necessary to assure the format of the weaving data before weaving was started on the loom. However, with the advancement of digital production, the weaving data can now be saved both in floppy disk and in Net server, and be sent to the jacquard controller electronically for production. Based on the design method described above, lack-and-white fabrics of photo-realistic effect with finer shade description can be developed digitally with reference to the fabric specification shown in Table 3. Figure 7 shows the comparison between subsequent black-and-white fabrics produced using the Jacquard Textile CAD System and its original digital colorless image. The advantages of designing jacquard in a colorless mode lie not only in traditional design method being renewed and the efficiency of fabric design being enhanced via the deployment of digital technologies, but also the creation of digital jacquard fabrics with picturesque effect being achieved which was otherwise not possible before. 41

7 Fig. 7. Effects of digital colorless image (left), real fabric (middle) and its details (right) 4. Conclusion The study for the design of colorless digital jacquard fabrics integrated basic principles in textile science, color science, and computer science. It sets yet another milestone in jacquard textile design and has remarkable impact on the present means of how jacquard fabrics have been designed over thousands of years. The products developed by digital design methods have completely removed any previous restrictions of manual laboring, and by such, have expanded the creative dimension of jacquard textiles. This provides not only more favorable conditions for the development of innovative single-layer jacquard fabrics, but also an effective theoretical basis for the future study of the design and development of digital colorful jacquard fabrics (Grosicki, 1977; Zhou, 2004). As a result of constant surge for innovative concept and design of digital jacquard fabrics, new design trends are vigorously pursued to re-invent conventions. REFERENCES [1] Grosicki, Z.J. 1975, Watson s Textile Design and Color, Seventh Edition, Newnes-Butterworths, London, pp [2] Grosicki, Z.J. 1977, Watson s Advanced Textile Design, Fourth Edition, Newnes-Butterworths, London, pp [3] Lee, Z.X. 2000, Electronic Jacquard Technology and New Fabric Pattern Design, Textile Press, China, pp [4] Weinsdorfer, H. 2004, 50 years of Weaving Technology, International Textile Bulletin, no. 3, pp [5] Zhou, J. 2002, Development of the black-white fabric with figure and scenery images by electronic jacquard, Journal of Textile Research, China, vol. 23, no. 1, Feb., p. 38. [6] Zhou, J. 2004, Digital jacquard fabric design in colorful mode, Journal of Donghua University (English Edition), China, vol. 21, no. 4, Aug., pp