This project research is aimed at blind people's existing methods of reading. It can't make the blind people effectively and quickly read complex graphic colors and clarify the specific meanings expressed by the figures. According to the classification of visual obstacles, it mainly serves the problem of blind people's low color recognition rate. From the blind people's demand for color, through field investigation and analysis of blind people's perception of color and problems encountered in using traditional color recognition methods to propose a way for blind people to read complex graphic colors. By making models of different combinations and sizes, and testing in various environments of blind people's life, the pros and cons of the experimental data are compared and analyzed, and the figure shapes and figure sizes that blind people can quickly touch and read are obtained. It provides an effective demonstration for the application of the blind people's reading of graphic color. According to the latest data from the World Health Organization's official website in 2017, the number of people with visual impairment worldwide is 253 million, including 36 million patients with complete blindness, 217 million with moderate to severe visual impairment, and 81% of blind patients or moderate to severe visual impairment are aged 50 years or above. In August 2017, (Metadata analysis in the UK, 2017) a meta-analysis in the UK showed that between 1980 and 2015, about 36 million of the world's 7.033 billion people were blind (48% of the population had a crude prevalence, 56% of the population were women), 216.6 million had moderate to severe visual impairment (55% of the population were women), and 189 million had mild visual impairment (54% of the population were women). This data is still changing over time.

Worldwide, there are many pieces of research on the related fields of the blind recognition image and graphics; but there are few pieces of research on the color field of the blind recognition image. The main types are: collecting light wave through the camera, converting light wave into sound, directly linking to the bone, and using the difference of sound frequency to "listen to color" (Harbison, 2012). Research on the environmental recognition of the visually impaired; through the high-speed camera, the world around the user is photographed, then the image is mapped onto a pair of OLED screens, and the visually impaired person can see the surrounding environment (Conrad, 2006). By designing a new type of tactile image generation structure, the new driver and the contact 1:n, a driving device sequentially drives a multiple of contacts and appropriately slows down the image refreshing speed without significantly affecting the touch experience (Yang et al., 2016). The tactile display system, which automatically collects image information and converts the image contour into vibration tactile stimulation is put on the back to perceive the figure (Juan et al., 2011). Based on the world's leading VSLAM technology, the intelligent device "eyes", enabling smart devices to fully understand the geometric features of the scene and reconstruct the environmental layout research with high precision (Yupeng, 2016).

The related researches of recognizing image color by touching image are as follows: ① the tight and alienated degree of micro fabric lines attached to cardboard helps blind people to recognize color, and at the same time, sequins, beads, and other small ornaments are added to the recognition system, so that users can recognize different color cardboard more easily (Santos, 2007). ② Use the "hue ring" to arrange the dots, which represent ten colors from red to purple. The basic colors are represented by bumps. The color of the clothes is perforated in the range of the hue ring (Sagawa et al., 2014). ③ On the paper of the specified size, the dots, and the lines are combined into different shapes to replace the color, and the special manufacturing process is used to make the concave and convex feeling, so that the blind person can touch to recognize the graphic color (Junyu et al., 2015).

2.1 Discover problems

In the actual investigation and interview, it is found that, (Figure 1), the concept of color is different for blind people of different levels; especially for those who are born completely blind, there is no concept of color in the mind of who is born blind; in general, people think that the world seen and perceived by born totally blind people is black. In fact, it is not black. It is empty and colorless; through the explanation, the blind people know what red means, what does blue mean, etc. They just know the meaning of the color, but accurately, they don't know what color is. If the blind people can feel black, it proves that the blind person is still sensitive, not blind.

Figure 1. Data collection and on-site interviews

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Trying to use existing method of reading color to paint (Figure 2), for the convenience of research, we replace Taiwan's method with A and Japan's method with B. Since the Philippines' method is more complicated, there are changes of material, it is not conducive to the performance of the complex colors of paintings, so they are excluded.

Figure 2. Comparison diagram of existing touch reading color method and painting works

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Among them, one square in group A represents one color, and 11 squares represent 11 colors; a whole cloth in group B represents one color, which is composed of different colors through the change of black dots; according to the existing way of touch reading color, try to make the existing graphics instead of colors to represent the painting content. As shown in Figure 3.

Figure 3. Existing painting works displayed in the way of touch reading color

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By observing Figure 3, it is found that whether it is A or B, the way of replacing the color cannot avoid the limitation of the area, and the area is far larger than the area of most of the color blocks in the painting, so that the pixels of the picture are very low, and the painting has been lost. The meaning of the expression, such a pixel has completely separated from the painting. Therefore, neither a nor B can be used to express paintings, convey the meaning of paintings and the charm of colors.

We have made a comparison analysis of existing way of touch reading the colors of graphs. As shown in Figure 4.

Figure 4. Common problem existing in the touch reading of the colors of graphs

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According to the above analysis, there are common problems in blind people's identification of graphic color patterns: first, unable to express complex color images (including painting works); second, unable to switch graphics and colors at will; in view of this problem, we carry on the research and the experiment to finally draw the conclusion.

3.1 User positioning

Based on the analysis results of user independent data, the user positioning mainly focuses on four aspects: blinding time, disability level, Braille cognitive level and work life background.

First of all, according to the time division of blindness, blind people are divided into congenital blindness and acquired blindness; through reading materials and on-site interviews, the born congenital blind people are called congenital blindness, who have never been stimulated by color, do not know what color is, and have no concept of color, among which the people without light sense are the most prominent. Acquired blindness is caused by other factors. This kind of people has been stimulated by color before and know what color is and what color represents. But with the extension of time, this kind of people will gradually forget what color is.

Taking the disability level of visual impairment as an example, this study adopts the grading table of blindness and low vision standards recommended by the World Health Organization (WHO) Geneva conference (WHO, 1973), as shown in Table 1. The grading of blind people and low vision disability is conducive to providing each blind person with relevant services suitable for their own touch reading.

According to WHO-1973 standard, there are five levels of blindness. Blind people without light sense can't perceive color. Their world has no color, even black. Explaination does not work for blind people without light sense. We can only explain what color represents. ; < 0.02 ~ light sense is divided into the fourth level of blind people. This kind of people can only perceive black. Due to the single color, there is no other color contrast stimulation, so it is difficult to understand the meaning of black. Volunteers are also required to explain it. ; < 0.05 ~ 0.02 (1.0m index) is divided into the third level of blind people. These people can only perceive black and white. With the contrast stimulation of two colors, they can feel part of the meaning of color. The meaning of other colors needs volunteers to explain. ; < 0.1 ~ 0.05 (2.5m index) is divided into the second level of low vision. This kind of people can only perceive a certain number of fuzzy colors. The meaning of specific and detailed colors also needs to be supplemented by volunteers. ; < 0.3 ~ 0.1 is classified as the first level of low vision. This kind of people can perceive fuzzy color. The meaning of specific color needs to be supplemented by volunteers. Under the premise of a healthy body, these five kinds of blind people can create colorful works of art using touch and hearing assistance. What they need is a way to touch and communicate colors.

Thirdly, according to the classification of Braille cognitive level, each blind person has a different cognitive level and reading speed; the complexity of English braille is divided into three levels. Level 1 Braille refers to the possible arrangement of each point in a unit that represents only one letter, number, punctuation or special Braille component symbol - this is a one-to-one conversion. In Braille for this grade, a single cell cannot represent a word or abbreviation. The second level Braille replaces the first level Braille to save space. In the second level Braille, cells can represent abbreviations of words. Many cell combinations have been created to represent common words. Level 3 braille is the last level of Braille, which is basically the Braille shorthand system. It is not used in publications because it has not been standardized. It contains more than 300 abbreviations of words and makes full use of vowel ellipsis. Besides, to shorten the length of the final document, the spacing between words and paragraphs is reduced. Sometimes punctuation is used instead of words.

Fourth, according to the background of work and life, the work of the blind can be divided into masseuses, attorneys, psychological counselors, TCM, translators, tellers, plucked musical instruments (musicians), writers, lawyers, and telephone operators. Among them, massage, Braille translation, and writers will often use fingers and palms. After a long time of exercise, the sensitivity of fingers and palms will be greatly improved, so as to improve the speed of touch reading.

3.2 List one of the categories of disability for the blind

According to the user positioning, acquired blindness, < 0.05 ~ 0.02 (1.0m index) is the third level of blind people, Braille level II, and the massage profession is analyzed in detail. These kinds of people have color memory, accumulate more experience of touch reading in learning Braille and work, can quickly touch and read objects, understand the shape and size of objects, which provides a favorable premise for the later study of blind touch reading graphics.

3.3 How to replace color: replacing color with graphics

The Blair Braille system is a six-point square (Louis, 1824), vertical rectangle. With a set of letters arranged in different ways and regularly followed, and blank space, there are 64 changes to represent the text (Figure 5).

Figure 5. Schematic diagram of Blair Braille system

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Figures are the most frequently contacted by the blind in life and learning; From another point of view, flattening Braille and connecting blind spots will also form some irregular figures (Figure 6).

Figure 6. Connect Blair Braille to a graphic

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After zooming in on the paintings, film and television works and images, you will find that all the images are composed of small pixel squares (Figure 7). These small squares have a clear location and assigned color values. The color and location of the small squares determine the appearance of the image. In essence, it also shows that the image is composed of small pixel squares. The size and precision of each image are determined by the number of small pixel blocks.

Figure 7. Analysis of pixel diagrams of paintings

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3.4 Graphic shape reasoning

Since the scope of life of the blind is relatively small, so the shape of the figure is summarized from two aspects of the blind: first, from the common figure that touched by the visually impaired people in daily life; second, from the common figure that touched by the visually impaired people in their learning life. In daily life, the blind will be familiar with all kinds of graphics from various auxiliary information. This is a potential way of learning. Classification is subconsciously done in the mind, from which to get different shapes of graphics. In learning and living, most of the knowledge of Braille, graphics (Susan, 2013), mathematics and so on are acquired in schools for the blind, and the teaching aids for the blind are important ways to acquire graphics; some special graphics will also be learned in other ways, such as the blind painting exhibition, etc. We have summed up the commonly used graphics in learning and living (Figure 8).

Figure 8. Schematic diagram of the shape

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Through the above reasoning research, the commonness of the graphics used in various scenes is extracted to guide the induction of graphics. Excluding the similar lines, 11 figures were extracted as the test objects, which are: regular circle, star, square, semicircle, horizontal rectangle, diamond, pentagon, regular triangle, vertical rectangle, cross shape and ellipse. These 11 graphs are the first stage of the graph instead of the color test. The final graph can only be determined after the test according to the specific data analysis. As shown in Figure 9.

Figure 9. 11 figures concluded

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This study conducted an experiment to find the size and layout size of the graphics and replacement color graphics that are most suitable for blind people to use.

4.1 Graphic layout form

4.1.1 Graphic layout size

The arrangement of blind spots in Braille is strictly defined (GB/T 15720-2008, 2008), which is divided into point diameter, point height, point distance, square distance, line spacing, etc.; the change of these parameters will change the reading speed of blind people and the habits of blind people. In order to make the blinds read faster, they should follow their reading habits, so we set the size by referring to the dot pitch in the Braille international standard when laying out the dimensions. For the sake of easy understanding, the meanings of the square distance, the point pitch and the point diameter are illustrated in detail in Figure 10.

Figure 10. Schematic diagram of point distance and square distance of Braille international

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According to "Braille Cell Dimensions", Tiresias - Scientific and Technological Reports, "Braille on folding Cartons", European Carton Makers Association, Sept 2005, European Standard Developments - CEN. Standard EN 15823 and PharmaBraille Braille font system announcement, Braille requirements in the United States, France, Germany, the United Kingdom, Italy and other countries (SteelDesign, 2009), As shown in Figure 11.

Figure 11. Braille standards in different countries around the world

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In order to clarify the national standards for Braille in different countries of the world, the data are summarized according to the above figures, as shown in Figure 12.

Figure 12. Chart summarizing Braille standards for different countries around the world

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Figure 12 clearly shows that the Braille point pitch in different national Braille standards is 2.03~2.92mm, which also includes the national Braille standard of China, which is 2.2~2.8mm; the resolution combined with finger tactile sensor is about 2.5mm, namely 10ppi (pixel per inch), which is far lower than the visual resolution. Therefore, the dimension of the Braille international standard is used for testing. Based on the above research, two kinds of figures are randomly selected according to the international standard of Braille, and the point distance in the international standard is taken as the size setting to make the basic model (Figure 13).

Figure 13. Figure size in accordance with Braille national standard

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4.1.2 Graphic arrangement

The arrangement of the graphs is mainly used for experimental tests to test the problems that will occur in a type of person in the blind reading the graph and to collect and analyze the experimental data. The international Braille uses the changeable combination of six points to express the text, which is only used to express the text; there is no more requirement on the graphics, and the graphics performance has continuity, mainly used to express the painting works. The combination and arrangement of the graphics are closely related to the pixels of the painting works. In this case, the arrangement of the pictures has no square distance. Therefore, in consideration of the performance of color and learning cost in the future, the point spacing of graph sorting is executed according to the Braille international standard; according to the 11 graphs deduced, the point spacing between every two graphs should be arranged within 2.28~2.92mm to form the test graph, as shown in Figure 14.

Figure 14. Arrangement and size of graphs

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4.2 Experimental model making

The experimental model was made by two ways of 3D printing: SLA and FDM.

4.2.1 SLA

Stereo lithography Apparatus is mainly used for making a fine 3D model, and the unit can be accurate to about 0.1mm. On the premise of strict compliance with the international standard size of Braille, hundreds of graphic modules have been made through SLA, one of which is used for experimental tests. At the same time, the remaining number of graphic modules are used to expand the application, combined with the aluminum alloy carved outer frame, to form a practical model; this conceptual design has passed the international patent search (patent processing) and was selected into the 13th China National Art Exhibition. The National Art Exhibition is the most authoritative and largest exhibition in China's art circle. It is also a unique national art evaluation system, which holds a major event every five years (Figure 15).

Figure 15. SLA 3D printing process and photo of finished model

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4.2.2 Fused deposition modeling

According to the technical requirements of 3D printing of FDM, the image pixel analysis is done; taking the cartoon Iron Man cartoon as an example, the shape and color of iron man are represented by using shape instead of color (Figure 16).

Figure 16. Image analysis using inductive graphics

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It can be concluded from Figure 16 that the way of replacing the color with the shape of graphics, the pixel is much higher than the existing way of replacing the shape with the color so that the shape and color of graphics can be better represented. This project is mainly to test the recognition of the figure by the blind, so only a single block graphic model was created in 3D printing.

In order to make the experiment more effective and comprehensive, under the premise that the point distance ratio conforms to the Braille international standard, the single block graphic model is scaled up by several values, namely: Braille international standard size, Braille international standard 1 time size, Braille International standard 2 times size, Braille international standard 3 times size, and then FDM 3D printing is carried out (Figure 17).

Figure 17. FDM 3D Printing process

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4.3 Experimental design

The experimental target is postnatal blindness, < 0.05 ~ 0.02 (1.0-meter index), the third level of blind people, the second level of Braille, and the massage profession. A total of 15 people are tested according to different sizes of the model.

Group A: 15 people use Braille international standard size

Group B: 15 people use Braille international standard 1 time size

Group C: 15 people use Braille international standard 2 time size

Group D: 15 people use Braille international standard 3 time size

Before they start touch reading, explain to groups A, B, C and D what graphics are in the test graphic square, so that they can fully understand the shape range and match their touch reading advantages for testing (Figure 18).

Figure 18. Photos of field test

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4.4 Experimental data analysis

While observing the experimental process, the characteristics of the four groups of experiments were analyzed: Inability to read the graphics, error-reading graphics and the problems in the process of reading. A form analysis based on experimental specific data was made (Table 2).

Groups	Average completion time of 15 people	Graphic shape reading result (Unit: per person)
Group A	128s	1	0	0	0	0	0	0	0	0	0	0
Group B	73s	2	0	1	0	0	0	0	0	0	0	0
Group C	26s	15	13	13	15	6	5	6	3	3	13	3
Group D	18s	15	14	15	15	7	6	6	6	4	15	7

Table 2. Test data analysis

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To help illustrate, the graphics are numbered (Figure 19).

Figure 19. Process of numbering graphs

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According to experimental data analysis and on-site interviews, the pixel sizes of Group C and Group D are most suitable; In the actual 3D model of the graph, under the premise of the same graph, the gap between the graph and the graph is very small, and it is easy to make a wrong judgment. Among them, No. 5 and No. 7, No. 6 and No. 9, No. 8 and No. 11 are the most obvious. According to the analysis results of the experimental data, the original 11 figures were adjusted (Figure 20).

Figure 20. Graphs determined by test results

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Through this research, it is found that the hearing and touch of the blind are more sensitive than the average person, and the research on the color of blind reading is relatively limited. In this research process, blind figure shape recognition is studied, which is a preliminary study on blind people's reading and painting works. Through the study of blind people, common graphic analysis and induction in daily life, on-the-spot investigation and national standards, the shape of the blind reading pattern is proposed. Through 3D printing technology, a single block model is made, and the model is used to test in a certain type of blind people. It is known that some figures are confused when blind people touch and read. According to the experimental test data and field interviews, 11 figures are adjusted. Through the final experimental data, 8 figures are determined to make the blind people touch and read quickly. In future research, the research of replacing the color with figure shape will be applied to blind painting exhibitions, blind teaching, blind art creation, blind film, social sharing, and other fields. We hope to help blind people open up new areas of touch reading through future research projects.