CN112463012B - Method for Consistent Display of Handwriting in Paper and Screen Synchronization - Google Patents

Abstract

The invention relates to the technical field of teaching appliances, and discloses a method for consistent display of handwriting in paper-screen synchronization. First, initialize, place physical paper on a tablet, connect the tablet and a display device, and arrange a rectangular frame on the virtual paper As the display reference information, set the scale factor of the virtual paper and the physical paper and the area position displayed in the current window; then, receive the pen tip position information collected in real time by the handwriting device, and compare the pen tip position information with the reference rectangle position data, and based on the comparison result Continuously adjusts the display area, tracking the pen tip position and centering the display in the relevant area where the current pen tip is located. The method for displaying handwriting consistency in the synchronization of paper and screen of the present invention senses the position of the pen tip on the physical paper in real time during the writing process, and displays the written handwriting on the screen in a consistent manner. The handwriting does not produce deformation, and the size of the displayed handwriting can be adjusted at will.

Description

Method for Consistent Display of Handwriting in Paper and Screen Synchronization

technical field

The invention relates to the technical field of teaching appliances, in particular to a method for consistent display of handwriting and handwriting in paper-screen synchronization.

Background technique

With the rapid development of electronic information technology, paper screen synchronization becomes possible. The so-called paper-screen synchronization means that while the user is holding an ordinary pen and writing on ordinary paper, the electronic handwriting device perceives the user's handwriting process and results in real time, and simultaneously displays and saves the handwriting data. Compared with traditional electronic handwriting devices, the advantage of paper-screen synchronization is that it fully conforms to the writing habit of hand-eye coordination, that is, during the entire writing process, the user's visual feedback is brought by the traces of the pen in the hand left on the paper. Instead of hand-eye separation during writing, as in traditional handwriting devices, visual feedback is generated by the screen.

However, in the paper-screen synchronization, due to the inconsistency in the size of the writing area of the handwriting device and the display device, the handwriting displayed on the screen is prone to font deformation, the writing area near the pen tip cannot be tracked and displayed in real time, and the handwriting cannot be adjusted at will. size, etc. These problems will greatly affect the user's feeling in the writing process and hinder the wide application of the paper-screen synchronization technology.

SUMMARY OF THE INVENTION

The purpose of the present invention is to address the deficiencies of the above-mentioned technologies, to provide a method for displaying the consistency of handwriting in the synchronization of paper and screen, to sense the position of the pen tip on the physical paper in real time during the writing process, and to display the consistency of the written handwriting. Displayed on the screen, it has the advantages of real-time tracking of the position of the pen tip, no deformation of the displayed handwriting, and the advantages of being able to adjust the size of the displayed handwriting at will.

In order to achieve the above-mentioned purpose, the method for consistent display of handwriting and handwriting in the synchronization of paper and screen designed by the present invention includes the following steps:

A) Initialization:

First, place the physical paper on the tablet, so that the four corners of the physical paper and the four corners of the data collection area of the tablet remain fixed and coincident throughout the writing process;

Then, connect the tablet and the display device, the display device obtains the device size specification information of the tablet, and according to the device size specification information, the display device creates a virtual paper, and the length and width of the virtual paper are kept in the same proportion as the size of the writing paper;

Next, neatly arrange rectangular boxes on the virtual paper as display reference information, and record the position information of the center point of each rectangular box in the virtual paper; the length and height of the rectangle are set according to the typical size of the Chinese characters written in the relevant application. For example, in the application of calligraphy practice for school-age children, the typical size of Chinese characters does not exceed 1.5cm×1.5cm, then the length and width of the rectangular frame are set to 1.5cm;

Finally, set the proportional coefficient R of the virtual paper and the physical paper, set the attribute parameters of the virtual paper according to the proportional coefficient R, set the virtual paper rectangular area currently displayed in the display window, the center point of the display window and the main display rectangular area of the display window; The value range of the scale coefficient R is R2≤R≤R1, R1 is the smaller of the ratio of the length and height of the display area to the length and height of the rectangular frame arranged on the virtual paper, indicating that the display area can display at least one handwriting, R2 The value of is related to the number of handwriting _NR that can be displayed simultaneously in the display area at most, _NR =(R1/R2 ² );

B) Simultaneous display of handwriting:

When the user writes on the physical paper, the tablet samples the trajectory of the pen tip movement in real time, and transmits the sampled pen tip position information to the display device in real time. Converted to virtual paper position coordinates;

Then, the display device judges whether the position coordinates of the virtual paper at this moment are in the main display area of the display window, and if it is in the main display area, the movement trajectory of the handwriting at the current moment is drawn in the display window, otherwise, according to the virtual paper at the current sampling point Paper position coordinates, in all the rectangular boxes arranged regularly, find the rectangular box whose center point is closest to the current virtual paper position coordinates, and move the display window so that the center point of the display window moves to the center point of the nearest rectangular box. position, and then draw the motion trajectory of the handwriting at the current moment in the display window, after finishing the drawing of the virtual paper position coordinates of the current sampling point, read the pen tip position information at the next sampling moment, and repeat the above operations until the writing process ends;

The display window refers to a display area opened up on the display device for synchronously displaying handwriting;

The main display area is a rectangular display area whose center point coincides with the center point of the display window. The area of the rectangular display area is smaller than the area of the display window. The purpose of setting the main display area is to always avoid placing the pen tip on the edge of the display window. ;

The consistent display means that the display device tracks the position of the pen tip on the physical paper in real time during the writing process, and places an area where the pen tip is currently located on the physical paper in the center area of the display window. It can adapt to the size of the display area, and the position and aspect ratio of the handwritten handwriting drawn on the virtual paper are consistent with the position and aspect ratio of the handwritten handwriting on the physical paper.

Preferably, described step A), comprises the steps:

A1) Start: the initialization step of the handwriting consistency display method in the paper-screen synchronization starts;

A2) Place the physical paper on the tablet, so that the four corners of the physical paper and the four corners of the data collection area of the tablet remain fixed and coincident throughout the writing process. The physical paper includes white paper without grids, and only Stationery paper with reference lines in the horizontal or vertical direction, and also includes field-shaped or rice-shaped practice paper for writing practice;

A3) Connect the tablet and the display device, the display device obtains the device size specification information of the tablet, and according to the device size specification information, the display device creates a virtual paper. In order to prevent the displayed handwriting from being deformed on the display device, the length of the virtual paper and width are kept in the same proportion as the size of writing paper;

The display device refers to a device with a display function, including smart phones, tablet computers, notebook computers, and desktop computers;

The virtual paper refers to a virtual resource that is virtually generated in a computer, can use a software drawing tool to draw patterns on the virtual paper, and can present the drawn content on a display device; the properties of the virtual paper include width and height;

Let the width and height of the physical paper be L1 and H1 respectively, and let the width and height of the virtual paper be L2 and H2 respectively, if H1=H2×r1, L1=L2×r2, and r1=r2, then the physical paper and the virtual paper are called The aspect ratio of the paper is the same; r1, r2 are scaling coefficients, 0<r1, r2<+∞;

The length and width of the physical paper are related to the size of the writing area of the tablet;

A4) neatly arrange rectangular frames on the virtual paper as display reference information, and record the position information of the center point of each rectangular frame in the virtual paper;

The neatly arranging rectangular boxes on the virtual paper refers to arranging the rectangular boxes on the virtual paper in the order from top to bottom and from left to right, and the overlapping area of any two arranged rectangular boxes is less than or equal to zero. A certain distance is set between the rectangular boxes in each column, and a certain blank area is left on the upper, lower, left and right parts of the virtual paper. The size of the blank area, the length and width of the rectangular frame are determined according to the requirements of the specific application; for example, in the application where the writing Chinese characters are predicted to be smaller, the rectangular frame can be set smaller; In the application scenario of printing field grids and rice grids, the size, arrangement position, edge, and white space between rectangular frame rows and columns arranged on the virtual paper are different from those printed on the physical paper. The size, arrangement position, edges, and white space between the rows and columns of the rectangular frame shall be consistent; in the application scenario where the horizontal or vertical reference lines are pre-printed on the physical paper, the height of the rectangular frame arranged on the virtual paper shall not exceed two horizontal lines. The distance of the reference line, and make the bottom edge of the rectangular box coincide with the horizontal reference line, the width of the rectangular box arranged on the virtual paper does not exceed the distance between the two vertical reference lines, and make the left side of the rectangular box coincide with the vertical reference line. The size of the blank area left on the upper, lower, left and right parts of the paper is consistent with the size of the corresponding blank area printed on the physical paper;

其中，

表示R＝1时，第i个矩形框的中心点在虚拟纸张中所处的位置；比例系数R的取值应能保证在相关的应用场景中至少一个汉字笔迹能被完整显示在显示窗口中；The attribute parameters of the virtual paper include the width L2 of the virtual paper, L2=L1×R; the height H2, H2=H1×R; wherein L1 and H1 represent the width and height of the physical paper respectively; the i-th rectangular frame arranged neatly The center point position information of

in,

Indicates the position of the center point of the i-th rectangular frame in the virtual paper when R=1; the value of the proportional coefficient R should ensure that at least one Chinese handwriting can be completely displayed in the display window in relevant application scenarios ;

表示第i个矩形框的中心点位置信息，1≤i≤n，n表示虚拟纸张上布置的矩形框个数，

其中

表示R＝1时，第i个矩形框的中心点在虚拟纸张中所处的位置；After this step, we get (L1, _H1 ,L2,H2,R,E1, _E2 ,...,Ei,..., _En ) where L1 and _H1 represent the width and height of the physical paper, L2 and H2 represents the width and height of the virtual paper, R represents the scale factor, L2=L1×R, H2=H1×R,

Indicates the position information of the center point of the i-th rectangular frame, 1≤i≤n, n denotes the number of rectangular frames arranged on the virtual paper,

in

Indicates the position of the center point of the i-th rectangular frame in the virtual paper when R=1;

A5) set the proportional coefficient R of virtual paper and physical paper, set the attribute parameter of virtual paper according to proportional coefficient R; Set the virtual paper rectangular area currently displayed in the display window and the center point of the display window and the main display rectangular area of the display window;

The value range of the scale coefficient R is R2≤R≤R1, R1 is the smaller of the ratio of the length and height of the display area to the length and height of the rectangular frame arranged on the virtual paper, indicating that the display area can display at least one handwriting, R2 The value of is related to the number of handwriting _NR that can be displayed simultaneously in the display area at most, _NR =(R1/R2) ² ;

表示第k个矩形框等比例缩放后的中心点，1≤k≤n；显示窗口的四个顶点由下式求得：The setting of the virtual paper rectangular area currently displayed in the display window, the center point of the display window, and the main display rectangle area of the display window refers to, in the initial state, selecting a rectangular frame, and placing the center point of the display window on the display window. On the center point of the rectangular box,

Represents the center point of the k-th rectangular box after proportional scaling, 1≤k≤n; the four vertices of the display window are obtained by the following formula:

The four vertices of the main display rectangular area of the display window are obtained by the following equations:

Among them, n represents the number of rectangular boxes arranged on the virtual paper, Width and Height represent the width and height of the display window respectively; 0<w<1 is the scale factor, which is used to adjust the proportion of the main display area to the display window;

A6) End: After the initialization step, preparations are made for the consistent display of the handwritten handwriting written on the physical paper synchronously on the display device.

Preferably, described step B), comprises the steps:

B1) Start: the start of the consistent display step of the handwriting consistency display method in the paper-screen synchronization;

B2) the display device receives a time-series position data collected from the handwriting board during the writing process, and the handwriting board collects the time-series position data s _i =( _xi , y _i ) where the pen tip is located on the physical paper area during the writing process;

作为参数，调用同步一致性显示子方法，得到该时刻笔尖在虚拟纸张上的时序位置数据为A_i＝(u_i,v_i)；更新后的当前显示窗口的四个顶点在虚拟纸张的位置坐标{(dx₁,dy₁),(dx₂,dy₂),(dx₃,dy₃),(dx₄,dy₄)}，更新后的当前显示窗口的中心点在虚拟纸张的位置坐标(Gx,Gy)，更新后的当前显示窗口的主显示区域四个顶点在虚拟纸张的位置坐标{(fx₁,fy₁),(fx₂,fy₂),(fx₃,fy₃),(fx₄,fy₄)}；B3) Display device synchronously and consistently display the time-series position data at this moment: with the time-series position data s _i =(x _i , y _i ) where the pen tip is on the physical paper area at the current moment, the four vertices of the current display window are on the virtual paper The position coordinates of {(dx ₁ ,dy ₁ ),(dx ₂ ,dy ₂ ),(dx ₃ ,dy ₃ ),(dx ₄ ,dy ₄ )}, the position coordinates of the center point of the current display window on the virtual paper ( Gx, Gy), the position coordinates of the four vertices of the main display area of the current display window on the virtual paper

As a parameter, call the synchronization consistency display sub-method, and obtain the time series position data of the pen tip on the virtual paper at this moment as A _i =( _{u i} ,vi ); the updated position of the four vertices of the current display window on the virtual paper Coordinates {(dx ₁ ,dy ₁ ),(dx ₂ ,dy ₂ ),(dx ₃ ,dy ₃ ),(dx ₄ ,dy ₄ )}, the updated position coordinates of the center point of the current display window on the virtual paper (Gx, Gy), the updated position coordinates of the four vertices of the main display area of the current display window on the virtual paper {(fx ₁ ,fy ₁ ),(fx ₂ ,fy ₂ ),(fx ₃ ,fy ₃ ), (fx ₄ ,fy ₄ )};

B4) Judging whether the handwriting process is finished: Judging whether the real-time position data of the pen tip transmitted by the handwriting board to the display device is finished, if it has ended, then jump to step B5), and the synchronous display process ends; otherwise, jump to step B2), continue Simultaneously display the next pen tip position data;

B5) End: the end of the consistent display step of the handwriting consistency display method in the paper-screen synchronization.

Preferably, described step B3), comprises the steps:

当前显示窗口的中心点在虚拟纸张的位置坐标(Gx,Gy)，当前显示窗口的主显示区域四个顶点在虚拟纸张的位置坐标{(fx₁,fy₁),(fx₂,fy₂),(fx₃,fy₃),(fx₄,fy₄)}；B31) Start: Assuming that the time series position data of the pen tip received by the display device at this moment is s _i =(x _i , y _i ), the position coordinates of the four vertices of the current display window on the virtual paper

The position coordinates (Gx, Gy) of the center point of the current display window on the virtual paper, the position coordinates of the four vertices of the main display area of the current display window on the virtual paper {(fx ₁ ,fy ₁ ),(fx ₂ ,fy ₂ ) ,(fx ₃ ,fy ₃ ),(fx ₄ ,fy ₄ )};

B32) Convert the position coordinates of the pen tip at the sampling moment sent from the tablet into the position coordinates of the virtual paper in the display device: u _i =x _i ×R, v _i =y _i ×R, get the pen tip in the virtual Paper coordinates A _i =( _{u i} ,vi ), where R is the scaling factor between virtual paper and physical paper set in the system initialization stage;

定义的矩形区域内；若是，则跳转至步骤B36)；否则，跳转至步骤B34)；B33) Determine whether the virtual coordinates are in the main display area of the display window: determine whether A _i =( _{u i} ,vi ) is in the main display area of the display window

In the defined rectangular area; if so, jump to step B36); otherwise, jump to step B34);

1≤i≤n中，计算A_i＝(u_i,v_i)与所有矩形框中心点

的距离，1≤i≤n，设

表示与A_i＝(u_i,v_i)距离最近的中心点，1≤k≤n；B34) According to the virtual coordinates A _i =(u _i ,v _i ), in all the regularly arranged rectangular frames, find out the rectangle frame with the virtual coordinates A _i =(u _i ,vi ₎ and the center point of the rectangular frame closest to the center point: In all

In 1≤i≤n, calculate A _i =( _{u i} ,vi ) and the center points of all rectangles

distance, 1≤i≤n, set

represents the closest center point to A _i =(u _i ,vi ₎ , 1≤k≤n;

并更新当前显示窗口的四个顶点在虚拟纸张的位置坐标{(dx₁,dy₁),(dx₂,dy₂),(dx₃,dy₃),(dx₄,dy₄)}，当前显示窗口的中心点在虚拟纸张的位置坐标(Gx,Gy)，当前显示窗口的主显示区域四个顶点在虚拟纸张的位置坐标{(fx₁,fy₁),(fx₂,fy₂),(fx₃,fy₃),(fx₄,fy₄)}；B35) Move the display window so that the center point of the display window is aligned with the center point of the nearest rectangular frame: move the center point of the display window to the center point of the kth rectangular frame

And update the position coordinates of the four vertices of the current display window on the virtual paper {(dx ₁ ,dy ₁ ),(dx ₂ ,dy ₂ ),(dx ₃ ,dy ₃ ),(dx ₄ ,dy ₄ )}, the current The position coordinates (Gx, Gy) of the center point of the display window on the virtual paper, the position coordinates of the four vertices of the main display area of the current display window on the virtual paper {(fx ₁ ,fy ₁ ),(fx ₂ ,fy ₂ ), (fx ₃ ,fy ₃ ),(fx ₄ ,fy ₄ )};

表示第k个矩形框等比例缩放后的中心点；显示窗口的四个顶点由下式更新：Specifically, the center point of the kth rectangular frame is used as the center point of the display window,

Represents the center point of the k-th rectangular box after the proportional scaling; the four vertices of the display window are updated by the following formulas:

The four vertices of the main display rectangular area of the display window are updated by:

Among them, Width and Height represent the width and height of the display window respectively; 0<w<1 is the proportional coefficient, which is used to adjust the proportion of the size of the main display area to the display window;

B36) in the main display area of the display window, the virtual paper position of the pen tip at this moment is displayed: call the drawing method, from the last sampling moment to the current sampling moment, the motion track of the pen tip on the virtual paper is drawn and displayed;

B37) End: indicate the end of the step of displaying the time-series position data of the pen tip at the sampling moment synchronously and consistently; return the time-series position data of the pen tip on the virtual paper at this moment as A _i =( _{u i} ,vi ); The position coordinates of the four vertices on the virtual paper {(dx ₁ ,dy ₁ ),(dx ₂ ,dy ₂ ),(dx ₃ ,dy ₃ ),(dx ₄ ,dy ₄ )}, the center point of the current display window is at The position coordinates of the virtual paper (Gx, Gy), the position coordinates of the four vertices of the main display area of the current display window on the virtual paper {(fx ₁ ,fy ₁ ),(fx ₂ ,fy ₂ ),(fx ₃ ,fy ₃ ),(fx ₄ ,fy ₄ )}.

Preferably, in the step A2), the writing area of the handwriting board is designed into a groove with a depth that can accommodate a number of physical paper thicknesses, the physical paper is put into the groove and fixed with a clip, and the depth of the groove is convenient for jamming the physical paper Make the four corners of the physical paper coincide with the four corners of the writing area without affecting normal writing.

Compared with the prior art, the present invention has the following advantages: real-time perception of the position of the pen tip on the physical paper during the writing process, and consistent display of the written handwriting on the screen, with real-time tracking of the position of the pen tip, display of The advantages of free handwriting without deformation and free adjustment of the displayed handwriting size are of great significance to the wide application of paper-screen synchronization technology, and will help school-age children to improve the efficiency of handwriting by automatically calculating the problems in writing by the computer. Base.

Description of drawings

Fig. 1 is the flow chart of the method for consistent display of handwriting in paper-screen synchronization of the present invention;

Fig. 2 is the concrete flow chart of step A) initialization among Fig. 1;

Fig. 3 is step B in Fig. 1) concrete flow chart of handwriting synchronous display;

FIG. 4 is a flowchart showing the synchronous display of each sampled data in step B3) in FIG. 3 .

Detailed ways

The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

A method for consistent display of handwriting in paper-screen synchronization, as shown in Figure 1, includes the following steps:

A) Initialization:

First, place the physical paper on the tablet, so that the four corners of the physical paper and the four corners of the data collection area of the tablet remain fixed and coincident throughout the writing process;

Then, connect the tablet and the display device, the display device obtains the device size specification information of the tablet, and according to the device size specification information, the display device creates a virtual paper, and the length and width of the virtual paper are kept in the same proportion as the size of the writing paper;

Next, neatly arrange rectangular boxes on the virtual paper as display reference information, and record the position information of the center point of each rectangular box in the virtual paper; the length and height of the rectangle are set according to the typical size of the Chinese characters written in the relevant application. For example, in the application of calligraphy practice for school-age children, the typical size of Chinese characters does not exceed 1.5cm×1.5cm, then the length and width of the rectangular frame are set to 1.5cm;

Finally, set the proportional coefficient R of the virtual paper and the physical paper, set the attribute parameters of the virtual paper according to the proportional coefficient R, set the virtual paper rectangular area currently displayed in the display window, the center point of the display window and the main display rectangular area of the display window;

The value range of the scale coefficient R is R2≤R≤R1, R1 is the smaller of the ratio of the length and height of the display area to the length and height of the rectangular frame arranged on the virtual paper, indicating that the display area can display at least one handwriting, R2 The value of is related to the number of handwriting _NR that can be displayed simultaneously in the display area at most, _NR =(R1/R2) ² ;

B) Simultaneous display of handwriting:

When the user writes on the physical paper, the tablet samples the trajectory of the pen tip movement in real time, and transmits the sampled pen tip position information to the display device in real time. Converted to virtual paper position coordinates;

Then, the display device judges whether the position coordinates of the virtual paper at this moment are in the main display area of the display window, and if it is in the main display area, the movement trajectory of the handwriting at the current moment is drawn in the display window, otherwise, according to the virtual paper at the current sampling point Paper position coordinates, in all the regularly arranged rectangular boxes, find the rectangular box whose center point is closest to the current virtual paper position coordinates, and move the display window so that the center point of the display window moves to the center point of the nearest rectangular box, Then draw the motion trajectory of the handwriting at the current moment in the display window, after finishing the drawing of the position coordinates of the virtual paper at the current sampling point, read the pen tip position information at the next sampling moment, and repeat the above operations until the writing process ends;

The display window refers to a display area opened up on the display device for synchronously displaying handwriting;

The main display area is a rectangular display area whose center point coincides with the center point of the display window. The area of the rectangular display area is smaller than that of the display window. The purpose of setting the main display area is to never place the pen tip on the edge of the display window;

Consistent display means that the display device tracks the position of the pen tip on the physical paper in real time during the writing process, and places the area where the pen tip is currently located on the physical paper in the center of the display window. The size of the displayed handwriting can be adjusted automatically. Adapting to the size of the display area, the position and aspect ratio of the handwritten handwriting drawn on the virtual paper are consistent with the position and aspect ratio of the handwritten handwriting on the physical paper.

Wherein as shown in Figure 2, step A) initialization, including the following steps:

A1) Start: the initialization step of the handwriting consistency display method in the paper-screen synchronization starts;

A2) Place the physical paper on the tablet, so that the four corners of the physical paper and the four corners of the data collection area of the tablet remain fixed and coincident throughout the writing process. The physical paper includes white paper without grids, only horizontal or Stationery with vertical reference lines, including field or rice-shaped practice paper for writing practice;

A3) Connect the tablet and the display device, the display device obtains the device size specification information of the tablet, and according to the device size specification information, the display device creates a virtual paper. In order to prevent the displayed handwriting from being deformed on the display device, the length of the virtual paper and width are kept in the same proportion as the size of writing paper;

Display devices refer to devices with display functions, including smartphones, tablet computers, notebook computers, and desktop computers;

Virtual paper refers to a virtual resource that is virtually generated in a computer, and can be used to draw patterns on virtual paper with software drawing tools, and can present the drawn content on a display device; the properties of virtual paper include width and height;

Let the width and height of the physical paper be L1 and H1 respectively, and let the width and height of the virtual paper be L2 and H2 respectively, if H1=H2×r1, L1=L2×r2, and r1=r2, then the physical paper and the virtual paper are called The aspect ratio of the paper is the same; r1, r2 are scaling coefficients, 0<r1, r2<+∞;

The length and width of the physical paper are related to the size of the writing area of the tablet;

A4) neatly arrange rectangular frames on the virtual paper as display reference information, and record the position information of the center point of each rectangular frame in the virtual paper;

Neatly arranging rectangular boxes on the virtual paper refers to arranging rectangular boxes on the virtual paper in the order from top to bottom and from left to right, and the overlapping area of any two arranged rectangular boxes is less than or equal to zero. Set a certain distance between the rectangular boxes, and leave a certain blank area on the upper, lower, left, and right parts of the virtual paper. The size, length and width of the rectangular frame are determined according to the requirements of the specific application; for example, in the application where the writing of Chinese characters is predicted to be smaller, the rectangular frame can be set smaller; in particular, the physical paper has pre-printed Tianzi grid , In the application scenario of the rice-character grid, the size, arrangement position, edge and rectangular frame row, space between columns, etc. of the rectangular frame arranged on the virtual paper are different from the size and arrangement position of the field-shaped or rice-character grid printed on the physical paper. , the margins and the white space between the rows and columns of the rectangular frame should be consistent; in the application scenario where the horizontal or vertical reference lines are pre-printed on the physical paper, the height of the rectangular frame arranged on the virtual paper should not exceed the distance between the two horizontal reference lines , and make the bottom edge of the rectangular box coincide with the horizontal reference line, the width of the rectangular box arranged on the virtual paper does not exceed the distance between the two vertical reference lines, and make the left side of the rectangular box coincide with the vertical reference line. The size of the blank area left in the lower, left and right parts is consistent with the size of the corresponding blank area printed on the physical paper;

其中，

表示R＝1时，第i个矩形框的中心点在虚拟纸张中所处的位置；比例系数R的取值应能保证在相关的应用场景中至少一个汉字笔迹能被完整显示在显示窗口中；The attribute parameters of the virtual paper include the width L2 of the virtual paper, L2=L1×R; the height H2, H2=H1×R; wherein L1 and H1 represent the width and height of the physical paper respectively; the i-th rectangular frame arranged neatly The center point position information of

in,

Indicates the position of the center point of the i-th rectangular frame in the virtual paper when R=1; the value of the proportional coefficient R should ensure that at least one Chinese handwriting can be completely displayed in the display window in relevant application scenarios ;

表示第i个矩形框的中心点位置信息，1≤i≤n，n表示虚拟纸张上布置的矩形框个数，

其中

表示R＝1时，第i个矩形框的中心点在虚拟纸张中所处的位置；After this step, we get (L1, _H1 ,L2,H2,R,E1, _E2 ,...,Ei,..., _En ) where L1 and _H1 represent the width and height of the physical paper, L2 and H2 represents the width and height of the virtual paper, R represents the scale factor, L2=L1×R, H2=H1×R,

Indicates the position information of the center point of the i-th rectangular frame, 1≤i≤n, n denotes the number of rectangular frames arranged on the virtual paper,

in

Indicates the position of the center point of the i-th rectangular frame in the virtual paper when R=1;

A5) set the proportional coefficient R of virtual paper and physical paper, set the attribute parameter of virtual paper according to proportional coefficient R; Set the virtual paper rectangular area currently displayed in the display window and the center point of the display window and the main display rectangular area of the display window;

The value range of the scale coefficient R is R2≤R≤R1, R1 is the smaller of the ratio of the length and height of the display area to the length and height of the rectangular frame arranged on the virtual paper, indicating that the display area can display at least one handwriting, R2 The value of is related to the number of handwriting _NR that can be displayed simultaneously in the display area at most, _NR =(R1/R2) ² ;

表示第k个矩形框等比例缩放后的中心点，1≤k≤n；显示窗口的四个顶点由下式求得：The setting of the virtual paper rectangular area currently displayed in the display window, the center point of the display window, and the main display rectangle area of the display window refers to, in the initial state, selecting a rectangular frame, and placing the center point of the display window on the display window. On the center point of the rectangular box,

Represents the center point of the k-th rectangular box after proportional scaling, 1≤k≤n; the four vertices of the display window are obtained by the following formula:

The four vertices of the main display rectangular area of the display window are obtained by the following equations:

Among them, n represents the number of rectangular boxes arranged on the virtual paper, Width and Height represent the width and height of the display window respectively; 0<w<1 is the scale factor, which is used to adjust the proportion of the main display area to the display window;

A6) End: After the initialization step, preparations are made for the consistent display of the handwritten handwriting written on the physical paper synchronously on the display device.

As shown in Figure 3, step B) synchronous display of handwriting, including the following steps:

B1) Start: the start of the consistent display step of the handwriting consistency display method in the paper-screen synchronization;

B2) the display device receives a time-series position data collected from the handwriting board during the writing process, and the handwriting board collects the time-series position data s _i =( _xi , y _i ) where the pen tip is located on the physical paper area during the writing process;

作为参数，调用同步一致性显示子方法，得到该时刻笔尖在虚拟纸张上的时序位置数据为A_i＝(u_i,v_i)；更新后的当前显示窗口的四个顶点在虚拟纸张的位置坐标{(dx₁,dy₁),(dx₂,dy₂),(dx₃,dy₃),(dx₄,dy₄)}，更新后的当前显示窗口的中心点在虚拟纸张的位置坐标(Gx,Gy)，更新后的当前显示窗口的主显示区域四个顶点在虚拟纸张的位置坐标{(fx₁,fy₁),(fx₂,fy₂),(fx₃,fy₃),(fx₄,fy₄)}；B3) Display device synchronously and consistently display the time-series position data at this moment: with the time-series position data s _i =(x _i , y _i ) where the pen tip is on the physical paper area at the current moment, the four vertices of the current display window are on the virtual paper The position coordinates of {(dx ₁ ,dy ₁ ),(dx ₂ ,dy ₂ ),(dx ₃ ,dy ₃ ),(dx ₄ ,dy ₄ )}, the position coordinates of the center point of the current display window on the virtual paper ( Gx, Gy), the position coordinates of the four vertices of the main display area of the current display window on the virtual paper

As a parameter, call the synchronization consistency display sub-method, and obtain the time series position data of the pen tip on the virtual paper at this moment as A _i =( _{u i} ,vi ); the updated position of the four vertices of the current display window on the virtual paper Coordinates {(dx ₁ ,dy ₁ ),(dx ₂ ,dy ₂ ),(dx ₃ ,dy ₃ ),(dx ₄ ,dy ₄ )}, the updated position coordinates of the center point of the current display window on the virtual paper (Gx, Gy), the updated position coordinates of the four vertices of the main display area of the current display window on the virtual paper {(fx ₁ ,fy ₁ ),(fx ₂ ,fy ₂ ),(fx ₃ ,fy ₃ ), (fx ₄ ,fy ₄ )};

B4) Judging whether the handwriting process is finished: Judging whether the real-time position data of the pen tip transmitted by the handwriting board to the display device is finished, if it has ended, then jump to step B5), and the synchronous display process ends; otherwise, jump to step B2), continue Simultaneously display the next pen tip position data;

B5) End: the end of the consistent display step of the handwriting consistency display method in the paper-screen synchronization.

Wherein, in step B3), the display device synchronously consistently displays the time sequence position data at this moment, including the following steps:

当前显示窗口的中心点在虚拟纸张的位置坐标(Gx,Gy)，当前显示窗口的主显示区域四个顶点在虚拟纸张的位置坐标{(fx₁,fy₁),(fx₂,fy₂),(fx₃,fy₃),(fx₄,fy₄)}；B31) Start: Assuming that the time series position data of the pen tip received by the display device at this moment is s _i =(x _i , y _i ), the position coordinates of the four vertices of the current display window on the virtual paper

The position coordinates (Gx, Gy) of the center point of the current display window on the virtual paper, the position coordinates of the four vertices of the main display area of the current display window on the virtual paper {(fx ₁ ,fy ₁ ),(fx ₂ ,fy ₂ ) ,(fx ₃ ,fy ₃ ),(fx ₄ ,fy ₄ )};

B32) Convert the position coordinates of the pen tip at the sampling moment sent from the tablet into the position coordinates of the virtual paper in the display device: u _i =x _i ×R, v _i =y _i ×R, get the pen tip in the virtual Paper coordinates A _i =( _{u i} ,vi ), where R is the scaling factor between virtual paper and physical paper set in the system initialization stage;

定义的矩形区域内；若是，则跳转至步骤B36)；否则，跳转至步骤B34)；B33) Determine whether the virtual coordinates are in the main display area of the display window: determine whether A _i =( _{u i} ,vi ) is in the main display area of the display window

In the defined rectangular area; if so, jump to step B36); otherwise, jump to step B34);

1≤i≤n中，计算A_i＝(u_i,v_i)与所有矩形框中心点

的距离，1≤i≤n，设

表示与A_i＝(u_i,v_i)距离最近的中心点，1≤k≤n；B34) According to the virtual coordinates A _i =(u _i ,v _i ), in all the regularly arranged rectangular frames, find out the rectangle frame with the virtual coordinates A _i =(u _i ,vi ₎ and the center point of the rectangular frame closest to the center point: In all

In 1≤i≤n, calculate A _i =( _{u i} ,vi ) and the center points of all rectangles

distance, 1≤i≤n, set

represents the closest center point to A _i =(u _i ,vi ₎ , 1≤k≤n;

并更新当前显示窗口的四个顶点在虚拟纸张的位置坐标

当前显示窗口的中心点在虚拟纸张的位置坐标(Gx,Gy)，当前显示窗口的主显示区域四个顶点在虚拟纸张的位置坐标{(fx₁,fy₁),(fx₂,fy₂),(fx₃,fy₃),(fx₄,fy₄)}；B35) Move the display window so that the center point of the display window is aligned with the center point of the nearest rectangle: move the center point of the display window to the center point of the kth rectangle

And update the position coordinates of the four vertices of the current display window on the virtual paper

The position coordinates (Gx, Gy) of the center point of the current display window on the virtual paper, the position coordinates of the four vertices of the main display area of the current display window on the virtual paper {(fx ₁ ,fy ₁ ),(fx ₂ ,fy ₂ ) ,(fx ₃ ,fy ₃ ),(fx ₄ ,fy ₄ )};

表示第k个矩形框等比例缩放后的中心点；显示窗口的四个顶点由下式更新：Specifically, the center point of the kth rectangular frame is used as the center point of the display window,

Represents the center point of the k-th rectangular box after the proportional scaling; the four vertices of the display window are updated by the following formulas:

The four vertices of the main display rectangular area of the display window are updated by:

Among them, Width and Height represent the width and height of the display window respectively; 0<w<1 is the proportional coefficient, which is used to adjust the proportion of the size of the main display area to the display window;

B36) in the main display area of the display window, the virtual paper position of the pen tip at this moment is displayed: call the drawing method, from the last sampling moment to the current sampling moment, the motion track of the pen tip on the virtual paper is drawn and displayed;

当前显示窗口的中心点在虚拟纸张的位置坐标(Gx,Gy)，当前显示窗口的主显示区域四个顶点在虚拟纸张的位置坐标{(fx₁,fy₁),(fx₂,fy₂),(fx₃,fy₃),(fx₄,fy₄)}。B37) End: indicate the end of the step of displaying the time-series position data of the pen tip at the sampling moment synchronously and consistently; return the time-series position data of the pen tip on the virtual paper at this moment as A _i =( _{u i} ,vi ); The position coordinates of the four vertices on the virtual paper

The position coordinates (Gx, Gy) of the center point of the current display window on the virtual paper, the position coordinates of the four vertices of the main display area of the current display window on the virtual paper {(fx ₁ ,fy ₁ ),(fx ₂ ,fy ₂ ) ,(fx ₃ ,fy ₃ ),(fx ₄ ,fy ₄ )}.

In addition, in the initialization step A2), the writing area of the handwriting board is designed to be a groove with a depth that can accommodate a number of physical paper thicknesses, the physical paper is put into the groove and fixed with a clip, and the depth of the groove is convenient for jamming the physical paper. The four corners of the paper coincide with the four corners of the writing area and do not affect normal writing.

The method for displaying the consistency of handwriting in the synchronization of paper and screen of the present invention can sense the position of the pen tip on the physical paper in real time during the writing process, and display the consistency of the written handwriting on the screen. The displayed handwriting does not deform, and the displayed handwriting size can be adjusted at will. lay the foundation.

Claims (5)

1. a method for showing the consistency of handwriting and handwriting in the synchronization of paper and screen, is characterized in that: comprise the steps: A) Initialization: First, place the physical paper on the tablet, so that the four corners of the physical paper and the four corners of the data collection area of the tablet remain fixed and coincident throughout the writing process; Then, connect the tablet and the display device, the display device obtains the device size specification information of the tablet, and according to the device size specification information, the display device creates a virtual paper, and the length and width of the virtual paper are kept in the same proportion as the size of the writing paper; Next, neatly arrange rectangular boxes on the virtual paper as display reference information, and record the position information of the center point of each rectangular box in the virtual paper; Finally, set the proportional coefficient R of the virtual paper and the physical paper, set the attribute parameters of the virtual paper according to the proportional coefficient R, set the virtual paper rectangular area currently displayed in the display window, the center point of the display window and the main display rectangular area of the display window; B) Simultaneous display of handwriting: When the user writes on the physical paper, the tablet samples the trajectory of the pen tip movement in real time, and transmits the sampled pen tip position information to the display device in real time. Converted to virtual paper position coordinates; Then, the display device judges whether the position coordinates of the virtual paper at this moment are in the main display area of the display window, and if it is in the main display area, the movement trajectory of the handwriting at the current moment is drawn in the display window, otherwise, according to the virtual paper at the current sampling point Paper position coordinates, in all the rectangular boxes arranged regularly, find the rectangular box whose center point is closest to the current virtual paper position coordinates, and move the display window so that the center point of the display window moves to the center point of the nearest rectangular box. position, and then draw the motion trajectory of the handwriting at the current moment in the display window, after finishing the drawing of the virtual paper position coordinates of the current sampling point, read the pen tip position information at the next sampling moment, and repeat the above operations until the writing process ends; The display window refers to a display area opened up on the display device for synchronously displaying handwriting; The main display area is a rectangular display area whose center point coincides with the center point of the display window. The area of the rectangular display area is smaller than the area of the display window. The purpose of setting the main display area is to never place the pen tip on the edge of the display window. ; The consistent display means that the display device tracks the position of the pen tip on the physical paper in real time during the writing process, and places an area where the pen tip is currently located on the physical paper in the center area of the display window. It can adapt to the size of the display area, and the position and aspect ratio of the handwritten handwriting drawn on the virtual paper are consistent with the position and aspect ratio of the handwritten handwriting on the physical paper. 2. according to the method for handwriting consistency display in the described paper screen synchronization of claim 1, it is characterized in that: described step A), comprises the steps: A1) Start: the initialization step of the handwriting consistency display method in the paper-screen synchronization starts; A2) Place the physical paper on the tablet, so that the four corners of the physical paper and the four corners of the data collection area of the tablet remain fixed and coincident throughout the writing process. The physical paper includes white paper without grids, and only Stationery paper with reference lines in the horizontal or vertical direction, and also includes field-shaped or rice-shaped practice paper for writing practice; A3) Connect the tablet and the display device, the display device obtains the device size specification information of the tablet, and according to the device size specification information, the display device creates a virtual paper. In order to prevent the displayed handwriting from being deformed on the display device, the length of the virtual paper and width are kept in the same proportion as the size of writing paper; The display device refers to a device with a display function, including smart phones, tablet computers, notebook computers, and desktop computers; The virtual paper refers to a virtual resource that is virtually generated in a computer, can use a software drawing tool to draw patterns on the virtual paper, and can present the drawn content on a display device; the properties of the virtual paper include width and height; Let the width and height of the physical paper be L1 and H1 respectively, and let the width and height of the virtual paper be L2 and H2 respectively, if H1=H2×r1, L1=L2×r2, and r1=r2, then the physical paper and the virtual paper are called The aspect ratio of the paper is the same; r1, r2 are scaling coefficients, 0<r1, r2<+∞; The length and width of the physical paper are related to the size of the writing area of the tablet; A4) neatly arrange rectangular frames on the virtual paper as display reference information, and record the position information of the center point of each rectangular frame in the virtual paper; The neatly arranging rectangular boxes on the virtual paper refers to arranging the rectangular boxes on the virtual paper in the order from top to bottom and from left to right, and the overlapping area of any two arranged rectangular boxes is less than or equal to zero. A certain distance is set between the rectangular boxes in each column, and a certain blank area is left on the upper, lower, left and right parts of the virtual paper. The size of the blank area, the length and width of the rectangular frame are determined according to the requirements of the specific application; in the application where the writing Chinese characters are predicted to be smaller, the rectangular frame can be set to be smaller; the physical paper has been pre-printed with Tian character grid , In the application scenario of the rice-character grid, the size, arrangement position, edge and rectangular frame row, space between the columns and the field-shaped or rice-shaped frame printed on the physical paper on the virtual paper, arrangement position, The margins and the white space between the rows and columns of the rectangular frame should be consistent; in the application scenario where the horizontal or vertical reference lines are pre-printed on the physical paper, the height of the rectangular frame arranged on the virtual paper should not exceed the distance between the two horizontal reference lines. Make the bottom edge of the rectangular box coincide with the horizontal reference line, the width of the rectangular box arranged on the virtual paper does not exceed the distance between the two vertical reference lines, and make the left side of the rectangular box coincide with the vertical reference line, on the upper and lower sides of the virtual paper , The size of the blank area left in the left and right parts is consistent with the size of the corresponding blank area printed on the physical paper; The attribute parameters of the virtual paper include the width L2 of the virtual paper, L2=L1×R; the height H2, H2=H1×R; wherein L1 and H1 represent the width and height of the physical paper respectively; the i-th rectangular frame arranged neatly The center point position information of

in

Indicates the position of the center point of the i-th rectangular frame in the virtual paper when R=1; the value of the proportional coefficient R should be able to ensure that at least one Chinese handwriting can be completely displayed in the display window in this application scenario; After this step, we get (L1, _H1 ,L2,H2,R,E1, _E2 ,...,Ei,..., _En ) where L1 and _H1 represent the width and height of the physical paper, L2 and H2 represents the width and height of the virtual paper, R represents the scale factor, L2=L1×R, H2=H1×R,

Indicates the position information of the center point of the i-th rectangular box

n represents the number of rectangular boxes arranged on the virtual paper,

in

Indicates the position of the center point of the i-th rectangular frame in the virtual paper when R=1; A5) set the proportional coefficient R of virtual paper and physical paper, set the attribute parameter of virtual paper according to proportional coefficient R; Set the virtual paper rectangular area currently displayed in the display window and the center point of the display window and the main display rectangular area of the display window; The setting of the virtual paper rectangular area currently displayed in the display window, the center point of the display window, and the main display rectangle area of the display window refers to, in the initial state, selecting a rectangular frame, and placing the center point of the display window on the display window. On the center point of the rectangular box,

Represents the center point of the k-th rectangular box after proportional scaling, 1≤k≤n; the four vertices of the display window are obtained by the following formula:

The four vertices of the main display rectangular area of the display window are obtained by the following equations:

Among them, n represents the number of rectangular boxes arranged on the virtual paper, Width and Height represent the width and height of the display window respectively; 0<w<1 is the scale factor, which is used to adjust the proportion of the main display area to the display window; A6) End: After the initialization step, preparations are made for the consistent display of the handwritten handwriting written on the physical paper synchronously on the display device. 3. according to the method for handwriting and handwriting consistency display in the described paper screen synchronization of claim 2, it is characterized in that: described step B), comprises the steps: B1) Start: the start of the consistent display step of the handwriting consistency display method in the paper-screen synchronization; B2) the display device receives a time-series position data collected from the handwriting board during the writing process, and the handwriting board collects the time-series position data s _i =( _xi , y _i ) where the pen tip is located on the physical paper area during the writing process; B3) Display device synchronously and consistently display the time-series position data at this moment: with the time-series position data s _i =(x _i , y _i ) where the pen tip is on the physical paper area at the current moment, the four vertices of the current display window are on the virtual paper The position coordinates of {(dx ₁ ,dy ₁ ),(dx ₂ ,dy ₂ ),(dx ₃ ,dy ₃ ),(dx ₄ ,dy ₄ )}, the position coordinates of the center point of the current display window on the virtual paper ( Gx, Gy), the position coordinates of the four vertices of the main display area of the current display window on the virtual paper {(fx ₁ ,fy ₁ ),(fx ₂ ,fy ₂ ),(fx ₃ ,fy ₃ ),(fx ₄ , fy ₄ )} as a parameter, call the synchronous consistent display sub-method, and obtain the time series position data of the pen tip on the virtual paper at this moment as A _i =( _{u i} ,vi ); the updated four vertices of the current display window are in The position coordinates of the virtual paper {(dx ₁ ,dy ₁ ),(dx ₂ ,dy ₂ ),(dx ₃ ,dy ₃ ),(dx ₄ ,dy ₄ )}, the center of the updated current display window is in the virtual The position coordinates of the paper (Gx, Gy), the updated position coordinates of the four vertices of the main display area of the current display window on the virtual paper {(fx ₁ ,fy ₁ ),(fx ₂ ,fy ₂ ),(fx ₃ , fy ₃ ),(fx ₄ ,fy ₄ )}; B4) Judging whether the handwriting process is finished: Judging whether the real-time position data of the pen tip transmitted by the handwriting board to the display device is finished, if it has ended, then jump to step B5), and the synchronous display process ends; otherwise, jump to step B2), continue Simultaneously display the next pen tip position data; B5) End: the end of the consistent display step of the handwriting consistency display method in the paper-screen synchronization. 4. the method for handwriting consistency display in the described paper screen synchronization according to claim 3, is characterized in that: described step B3), comprises the steps: B31) Start: Assuming that the time series position data of the pen tip received by the display device at this moment is s _i =( _xi , y _i ), the position coordinates of the four vertices of the current display window on the virtual paper {(dx ₁ , dy ₁ ), (dx ₂ ,dy ₂ ),(dx ₃ ,dy ₃ ),(dx ₄ ,dy ₄ )}, the position coordinates (Gx, Gy) of the center point of the current display window on the virtual paper, the main display area of the current display window The position coordinates of the four vertices on the virtual paper {(fx ₁ ,fy ₁ ),(fx ₂ ,fy ₂ ),(fx ₃ ,fy ₃ ),(fx ₄ ,fy ₄ )}; B32) Convert the position coordinates of the pen tip at the sampling moment sent from the tablet into the position coordinates of the virtual paper in the display device: u _i =x _i ×R, v _i =y _i ×R, get the pen tip in the virtual Paper coordinates A _i =( _{u i} ,vi ), where R is the scaling factor between virtual paper and physical paper set in the system initialization stage; B33) Determine whether the virtual coordinates are in the main display area of the display window: determine whether A _i =( _{u i} ,vi ) is in {(fx ₁ ,fy ₁ ),(fx ₂ ,fy ₂ ),(fx ₃ ,fy ₃ ), (fx ₄ , fy ₄ )} within the defined rectangular area; if so, jump to step B36); otherwise, jump to step B34); B34) According to the virtual coordinates A _i =(u _i ,v _i ), in all the regularly arranged rectangular frames, find out the rectangle frame with the virtual coordinates A _i =(u _i ,vi ₎ and the center point of the rectangular frame closest to the center point: In all

, calculate A _i =( _{u i} ,vi ) and the center points of all rectangular boxes

distance, 1≤i≤n, set

represents the closest center point to A _i =(u _i ,vi ₎ , 1≤k≤n; B35) Move the display window so that the center point of the display window is aligned with the center point of the nearest rectangular frame: move the center point of the display window to the center point of the kth rectangular frame

And update the position coordinates of the four vertices of the current display window on the virtual paper {(dx ₁ ,dy ₁ ),(dx ₂ ,dy ₂ ),(dx ₃ ,dy ₃ ),(dx ₄ ,dy ₄ )}, the current The position coordinates (Gx, Gy) of the center point of the display window on the virtual paper, the position coordinates of the four vertices of the main display area of the current display window on the virtual paper {(fx ₁ ,fy ₁ ),(fx ₂ ,fy ₂ ), (fx ₃ ,fy ₃ ),(fx ₄ ,fy ₄ )}; Specifically, the center point of the kth rectangular frame is used as the center point of the display window,

Represents the center point of the k-th rectangular box after the proportional scaling; the four vertices of the display window are updated by the following formulas:

The four vertices of the main display rectangular area of the display window are updated by:

Among them, Width and Height represent the width and height of the display window respectively; 0<w<1 is the proportional coefficient, which is used to adjust the proportion of the size of the main display area to the display window; B36) in the main display area of the display window, the virtual paper position of the pen tip at this moment is displayed: call the drawing method, from the last sampling moment to the current sampling moment, the motion track of the pen tip on the virtual paper is drawn and displayed; B37) End: indicate the end of the step of displaying the time-series position data of the pen tip at the sampling moment synchronously and consistently; return the time-series position data of the pen tip on the virtual paper at this moment as A _i =(u _i ,v _i ); The position coordinates of the four vertices on the virtual paper {(dx ₁ ,dy ₁ ),(dx ₂ ,dy ₂ ),(dx ₃ ,dy ₃ ),(dx ₄ ,dy ₄ )}, the center point of the current display window is at The position coordinates of the virtual paper (Gx, Gy), the position coordinates of the four vertices of the main display area of the current display window on the virtual paper {(fx ₁ ,fy ₁ ),(fx ₂ ,fy ₂ ),(fx ₃ ,fy ₃ ),(fx ₄ ,fy ₄ )}. 5. according to the method for consistent display of handwriting in the described paper screen synchronization of claim 2, it is characterized in that: in the described step A2), the handwriting board writing area is designed into a groove that can accommodate some physical paper thicknesses in depth, The physical paper is put into the groove and fixed with a clip. The depth of the groove is convenient for clamping the physical paper so that the four corners of the physical paper coincide with the four corners of the writing area without affecting normal writing.

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