Method and device for generating interframe color-imitated pattern in FRC

Abstract

The invention provides a method and a device for generating an inter-frame color-imitating pattern in FRC. The method comprises the following steps: determining a color depth difference value between a color depth to be displayed and a color depth of a display screen; wherein the to-be-displayed color depth is higher than the color depth; according to the color depth difference value, determining the size and the type of the color-imitated pattern, and screening out a key type from the types; according to the color depth difference value, the color-imitating pattern corresponding to each key type is divided, and a plurality of basic patterns are obtained; determining a reference pattern from the basic pattern, dividing the reference pattern to obtain a plurality of unit patterns, and transforming and splicing the unit patterns to obtain a color-imitating pattern of each frame; wherein the number of the reference patterns is the same as that of the key types. According to the scheme, the chip area occupied by the stored color-imitated patterns is reduced, meanwhile, more kinds of color-imitated patterns can be flexibly generated, and the color shaking effect is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of image processing, and in particular to a method and device for generating an inter-frame dithering pattern in FRC. Background Art

[0002] Each digital image is composed of many pixels. The light source behind each sub-pixel can show different brightness levels, which are called grayscale. The more grayscales there are between the darkest and the brightest, the more delicate the image effect can be.

[0003] The pixel width of the source driver chip of the existing display system is usually 6 bits or 8 bits. In order to reduce costs, the frame rate control dithering (FRC-Dither) method is usually used to display more grayscales with fewer grayscales, for example, using a 6-bit screen to display 8-bit image data. However, when using the FRC-Dither method, it is necessary to store the dithering patterns used in the processing process, and storing all the dithering patterns will use more storage units, which will also occupy more chip area; at the same time, as the chip functions increase and the size decreases, the chip area occupied by storing the dithering patterns can be reduced by storing some dithering patterns. However, storing some dithering patterns will limit the types of dithering patterns for each grayscale, which has poor flexibility when changing between frames and will result in poor dithering effects. Therefore, it is urgent to provide a method and device for generating inter-frame dithering patterns in FRC. Summary of the invention

[0004] The present invention provides a method and device for generating inter-frame dithering patterns in FRC, which can generate more types of dithering patterns while reducing the chip area occupied by storing dithering patterns through storage unit patterns, have higher flexibility and improve the dithering effect.

[0005] In a first aspect, the present invention provides a method for generating an inter-frame dithering pattern in an FRC, the method comprising:

[0006] Determining a color depth difference between a color depth to be displayed and a color depth of a display screen; wherein the color depth to be displayed is higher than the color depth;

[0007] Determining the size and type of the dither pattern according to the color depth difference, and selecting key types from the types;

[0008] Dividing the dither pattern corresponding to each of the key categories according to the color depth difference to obtain a plurality of basic patterns;

[0009] A reference pattern is determined from the basic pattern, and the reference pattern is divided to obtain a plurality of unit patterns, so as to obtain a dithered pattern that changes in each frame by transforming and splicing the unit patterns; wherein the number of the reference patterns is the same as the number of the key types.

[0010] In a second aspect, the present invention further provides a device for generating an inter-frame dithering pattern in an FRC, comprising:

[0011] A color depth difference determination module, used to determine the color depth difference between the color depth to be displayed and the color depth of the display screen; wherein the color depth to be displayed is higher than the color depth;

[0012] a dither pattern determination module, configured to determine the size and type of the dither pattern according to the color depth difference, and select key types from the types;

[0013] A processing module is used to divide the dither pattern corresponding to each of the key categories according to the color depth difference to obtain a plurality of basic patterns; and determine a reference pattern from the basic patterns, divide the reference pattern to obtain a plurality of unit patterns, so as to obtain a dither pattern that changes in each frame by transforming and splicing the unit patterns; wherein the number of the reference patterns is the same as the number of the key categories.

[0014] In a third aspect, the present invention further provides a computing device, comprising a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, it implements any one of the above-mentioned methods for generating an inter-frame dithering pattern in an FRC.

[0015] In a fourth aspect, the present invention further provides a computer-readable storage medium having a computer program stored thereon, which, when executed in a computer, causes the computer to execute any one of the above-mentioned methods for generating an inter-frame dithering pattern in an FRC.

[0016] In a fifth aspect, an embodiment of the present invention further provides a computer program product, comprising computer instructions, which, when executed by a processor, implement the steps of the method described in any first aspect of this specification.

[0017] The present invention provides a method and device for generating inter-frame dithering patterns in FRC. After determining the color depth difference between the color depth to be displayed and the color depth of the display screen, the method determines the size and type of the dithering pattern based on the color depth difference, and then reduces the dithering patterns that need to be stored by screening key types; divides the dithering patterns corresponding to the key types to obtain a number of basic patterns, and then further screens the reference patterns that need to be stored from the basic patterns, and further divides the reference patterns into smaller unit patterns, and finally transforms and splices the unit patterns to obtain the dithering patterns that change in each frame. In this way, the unit patterns that need to be stored are obtained by two screenings and two divisions, and there is no need to store all the dithering patterns used in the frame rate control dithering algorithm, and a variety of different dithering patterns can be generated through the stored unit patterns, which not only reduces the area required for the chip to store the dithering patterns, but also has higher flexibility and improves the dithering effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a 4*4 dithering pattern provided by the present invention;

[0019] Figure 2 is a flow chart of a method for generating an inter-frame dithering pattern in FRC provided by an embodiment of the present invention;

[0020] Figure 3 is a schematic diagram of a basic pattern obtained by dividing a dither pattern provided by an embodiment of the present invention;

[0021] Figure 4 is a unit pattern provided by an embodiment of the present invention;

[0022] Figure 5 is a transformation schematic diagram using a third transformation combination provided by an embodiment of the present invention;

[0023] Figures 6 to 8 They are respectively a first reference pattern provided by an embodiment of the present invention;

[0024] Figures 9 to 14 They are respectively a second reference pattern provided by an embodiment of the present invention;

[0025] Fig.15 , Fig.16 They are respectively a third reference pattern provided by an embodiment of the present invention;

[0026] Figures 17 to 20 They are respectively a fourth reference pattern provided by an embodiment of the present invention;

[0027] Fig.21 is a schematic diagram of a transformation using a first matrix transformation provided by an embodiment of the present invention;

[0028] Fig. 22 is a schematic diagram of a transformation using a second matrix transformation provided by an embodiment of the present invention;

[0029] Fig.23 is a schematic diagram of a transformation using a third matrix transformation provided by an embodiment of the present invention;

[0030] Fig.24 is a schematic diagram of a transformation using a fourth matrix transformation provided by an embodiment of the present invention;

[0031] Fig.25 A transformation flow chart of a dithered pattern obtained by transforming and splicing a reference pattern provided by an embodiment of the present invention;

[0032] Fig.26 is a hardware architecture diagram of a computing device provided by an embodiment of the present invention;

[0033] Fig. 27 It is a structural diagram of an inter-frame dithering pattern generating device in FRC provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0035] For the traditional FRC-Dither principle. For example, for 8-bit input data, a 6-bit screen is usually used for display, so the color depth to be displayed is 8-bit, and the color depth of the display screen is 6-bit. Although the 6-bit screen can only display 64 grayscales, for the 256 grayscales of 8-bit to be displayed; among them, the 0th, 4th, 8th, 4m and other grayscales are displayed directly, while the grayscales 4m+1, 4m+2, 4m+3 are realized by the spatial-temporal averaging of FRC-Dither.

[0036] Dither refers to the intra-frame averaging in the spatial domain. For example, to display the 129th order (32.25th order of 6bit), it is necessary to display a 132th order (33rd order of 6bit) and three 128th orders (32nd order of 6bit) in each 2*2 unit in the entire image, and achieve an average grayscale of 129th order through spatial averaging, that is, (132+128*3) / 4=129. Similarly, other grayscale levels can be achieved. The above-mentioned 2*2 unit can also select other sizes, such as 4*4, 8*8, etc., as long as the ratio of 132th order (4n+4) and 128th order (4n) is 1:3, 2:2, 3:1, the corresponding 4n+1, 4n+2, 4n+3 can be achieved. For each pixel in each unit, whether it is displayed as 4n or 4n+4 is achieved by searching the dither pattern (Dither Pattern) according to the row and column positions; Figure 1 Shown is a 4*4 dither pattern showing 4n+1 steps.

[0037] FRC refers to the inter-frame average in the time domain. Taking the display of 129 levels as an example, in the adjacent 4 frames, for each pixel, the ratio of 128 levels to 132 levels is still maintained at 3:1, so that the average grayscale of the pixel is 129 levels. This requires that the dithering pattern of each frame is different.

[0038] Please refer to Figure 2 The embodiment of the present invention provides a method for generating an inter-frame dithering pattern in FRC, comprising:

[0039] Step 200, determining a color depth difference between a color depth to be displayed and a color depth of a display screen; wherein the color depth to be displayed is higher than the color depth;

[0040] Step 202, determining the size and type of the dither pattern according to the color depth difference, and selecting key types from the types;

[0041] Step 204, dividing the dither pattern corresponding to each key category according to the color depth difference to obtain a plurality of basic patterns;

[0042] Step 206, determining a reference pattern from the basic pattern, dividing the reference pattern into a plurality of unit patterns, and obtaining a dithered pattern that changes in each frame by transforming and splicing the unit patterns; wherein the number of the reference patterns is the same as the number of the key types.

[0043] In the present invention, after determining the color depth difference between the color depth to be displayed and the color depth of the display screen, the size and type of the dither pattern are determined based on the color depth difference, and then the dither patterns that need to be stored are reduced by screening key types; a number of basic patterns are obtained by dividing the dither patterns corresponding to the key types, and then the reference patterns that need to be stored are further screened from the basic patterns, and the reference patterns are further divided into smaller unit patterns, and finally the dither patterns that change in each frame are obtained by transforming and splicing the unit patterns. In this way, the unit patterns that need to be stored are finally obtained by two screenings and two divisions, and there is no need to store all the dither patterns used in the frame rate control dithering algorithm, and a variety of different dither patterns can be generated through the stored unit patterns, which not only reduces the area required for the chip to store the dither pattern, but also has higher flexibility and improves the dithering effect.

[0044] Described below Figure 2 How the various steps are performed.

[0045] In step 200, the color depth is represented by the number of bits. The more bits there are, the more grayscales there are, the more colors there are available, and the more delicate the colors are. The number of grayscales is equal to 2 raised to the power of the number of color depth bits. In addition, the frame rate control dithering (FRC-Dither) method can display more grayscales with fewer grayscales, so it is necessary to satisfy that the color depth to be displayed is higher than the color depth.

[0046] In step 202, the size and type of the dither pattern are determined according to the color depth difference, including:

[0047] The size of the dither pattern is determined according to the color depth difference; wherein the size is n 2 *n 2 ; n is the color depth difference;

[0048] The type and number of dither patterns are determined according to the size; the ratio of the number of carry pixels to the number of non-carry pixels in different types is different, and the number of types is n. 2 -1.

[0049] Specifically, taking a 6-bit screen displaying a 10-bit (color depth to be displayed) grayscale as an example, that is, the color depth difference is 4, and grayscales 16m+1, 16m+2, ... 16m+15 need to be realized by FRC-Dither on an average basis. According to the principle of the traditional FRC-Dither method, the size of the dither pattern (Dither_Pattern) is required to be at least 4*4 units, so that the ratio of the number of carry pixels to the number of non-carry pixels in the dither pattern can meet the ratio of 0:16, 1:15, 2:14, 3:13, 4:12, 5:11, 6:10, 7:9, 8:8, 9:7, 10:6, 11:5, 12:4, 13:3, 14:2, 15:1 and 16:0, and grayscales from 16m to 16m+16 can be displayed. In the present invention, by requiring that the above ratio can also be satisfied within the adjacent minimum 16*1 units in the row and column directions of the screen, the size of the dither pattern is limited to 16*16 (i.e., n 2 *n 2 ), can further improve spatial averaging and enhance visual display effects.

[0050] In the present invention, as described in the previous example, since the ratio of the number of carry pixels to the number of non-carry pixels in the dither pattern is 0:16 and 16:0, the gray scale of 16m and the gray scale of 16m+16 are displayed respectively, the color depth of the display screen can be directly displayed. Therefore, there are only 15 types of actual dither patterns, including the ratios of the number of carry pixels to the number of non-carry pixels of 1:15, 2:14, 3:13, 4:12, 5:11, 6:10, 7:9, 8:8, 9:7, 10:6, 11:5, 12:4, 13:3, 14:2, and 15:1 respectively.

[0051] In a preferred embodiment, a two-dimensional binary matrix is ​​used to represent the dither pattern; wherein the size of the two-dimensional binary matrix is ​​the same as the dimension; when the matrix element value of the two-dimensional binary matrix is ​​1, it represents a carry pixel, and when the matrix element value is 0, it represents a non-carry pixel;

[0052] Filter out key categories from the categories, including:

[0053] A binary code is used to represent the number of carry pixels in a two-dimensional binary matrix;

[0054] The actual values ​​corresponding to the binary codes whose least significant bits are even are sorted from small to large, and the types of dithering patterns represented by the two-dimensional binary matrices corresponding to the first n binary codes are used as key types; n is the color depth difference;

[0055] The two-dimensional binary matrix of the dither pattern corresponding to the key category is inverted by using a logical NOT operator to obtain a two-dimensional binary matrix of the dither pattern corresponding to the first category; the dither pattern corresponding to the binary code whose least significant bit is an even number is alternately displayed between frames to obtain a dither pattern corresponding to the binary code whose least significant bit is an odd number corresponding to the second category; wherein the category consists of the key category, the first category and the second category.

[0056] It should be noted that the dither pattern used in the current frame can be represented as a two-dimensional binary matrix: Dither_Pattern[i,j], i∈(0,n 2 -1), j∈(0,n 2 -1); n is the color depth difference. Among them, i, j represent the row and column position coordinates of the matrix, that is, corresponding to the i-th row and j-th column. The actual FRC-Dither process is to find the corresponding matrix element value of the pixel in the matrix. When the corresponding matrix element value is 1, the pixel is a carry pixel, and the higher order of the two adjacent grayscales needs to be displayed, that is, the grayscale output at the pixel position is 16m+16; when the corresponding matrix element value is 0, the pixel is a non-carry pixel, and the lower order of the two adjacent grayscales needs to be displayed, that is, the grayscale output at the pixel position is 16m.

[0057] Specifically, taking a 6-bit screen displaying 10-bit grayscale as an example, the number of types is 15. As described in the previous example, the binary codes used to represent the number of carry pixels in the two-dimensional binary matrix of these 15 types of dither patterns are 0001, 0010, 0011, 0100, 0101, 0110, 0111, 1000, 1001, 1010, 1011, 1100, 1101, 1110, 1111. The binary codes with the least significant bit being an even number correspond to The actual values ​​of are sorted from small to large, and the resulting sequence is 0010, 0100, 0110, 1000, 1010, 1100, 1110. The top four binary codes are 0010 (the number of pixels with carry is 2), 0100 (the number of pixels with carry is 4), 0110 (the number of pixels with carry is 6), and 1000 (the number of pixels with carry is 8). The key type is the type of dithering pattern represented by the two-dimensional binary matrix corresponding to these four binary codes. At this time, the two-dimensional binary matrices with binary codes of 1110, 1100, and 1010 can be obtained by performing the inversion operation on the two-dimensional binary matrices with binary codes of 0010, 0100, and 0110, respectively. For the binary codes 0001, 0011, 0101, 0111, 1001, 1011, 1101, 1111 whose least significant bits are odd, the two-dimensional binary matrix can be obtained by alternating the color patterns corresponding to the adjacent binary codes whose least significant bits are even through inter-frame appearance according to a principle similar to FRC; for example, the two-dimensional binary matrix of the binary code 0011 can be realized by alternating the two-dimensional binary matrices whose binary codes are 0010 and 0100 through inter-frame appearance.

[0058] Therefore, in the present invention, all dither patterns required in the dither algorithm can be obtained by processing n key types of dither patterns, so only the reference patterns corresponding to the n dither patterns need to be stored. However, although storing only n types of dither patterns reduces the chip area occupied by storing dither patterns, it limits the types of dither patterns for each grayscale, which is not flexible enough in application. Therefore, this problem is solved by storing unit patterns constituting the n types of dither patterns.

[0059] In step 204, the dither pattern corresponding to each key category is divided according to the color depth difference to obtain several basic patterns, including:

[0060] According to the color depth difference, the size of the basic pattern is determined; wherein the size of the basic pattern is n*n; n is the color depth difference;

[0061] According to the size of the basic pattern, the dither pattern corresponding to the key category is divided in order from left to right and from top to bottom to obtain n 2 A basic pattern.

[0062] Specifically, following the previous example, taking a 6-bit screen displaying a 10-bit grayscale as an example, the size of the dither pattern is 16*16, and the dither pattern is divided into the following Figure 3 The 16 4*4 basic patterns shown are called sub_pat00, sub_pat01, sub_pat02, sub_pat03, sub_pat10, sub_pat11, sub_pat12, sub_pat13, sub_pat20...sub_pat33 in sequence.

[0063] In a preferred embodiment, the size of the unit pattern is 2*2; the reference pattern includes at least two unit patterns; wherein, four types of unit patterns are included, and the number of carry pixels in the same type of unit patterns is the same, and the positions of carry pixels in different unit patterns are different.

[0064] In a preferred embodiment, the color depth difference is preferably 4 or 2. When the color depth difference is 2, the reference unit is the unit pattern.

[0065] Specifically, the unit pattern includes Figure 4 There are 4 types shown, a total of 11 unit patterns, and the position of the carry pixel of each unit pattern is different. Figure 4 There are four types, namely the first type pata (the number of carry pixels is 1, and there are four unit patterns: pata_0, pata_1, pata_2, and pata_3), the second type patb (the number of carry pixels is 2, and there are two unit patterns: patb_0 and patb_1), the third type patc (the number of carry pixels is 2, and there are four unit patterns: patc_0, patc_1, patc_2, and patc_3), and the fourth type pat0 (the number of carry pixels is 0, and there is one unit pattern pat0).

[0066] In step 206, when the color depth difference is 4, the dither pattern that changes in each frame is obtained by transforming and splicing the unit patterns, including:

[0067] S1: Select a reference pattern consisting of 4 unit patterns;

[0068] S2: transform and combine the composed reference patterns to obtain multiple frame reference patterns;

[0069] S3: transform and splice each frame of the reference pattern to obtain a transformed dithered color pattern for each frame.

[0070] Taking a 6-bit screen displaying 10-bit grayscale as an example, the size of the reference pattern is 4*4, and as mentioned in the previous example, 0010, 0100, 0110, 1000, then the key types are the types of dithering patterns represented by the two-dimensional binary matrix corresponding to the four binary codes 0010, 0100, 0110, 1000, and the reference pattern corresponding to 0010 is recorded as the first reference pattern of gray2, the reference pattern corresponding to 0100 is recorded as the second reference pattern of gray4, the reference pattern corresponding to 0110 is recorded as the third reference pattern of gray6, and the reference pattern corresponding to 1000 is recorded as the fourth reference pattern of gray8. Combined with Figure 4 As shown, the 4*4 first reference pattern of gray2 can be composed of pat0 and pata; the 4*4 second reference pattern of gray4 can be composed of pata, or composed of patb and pat0, or composed of patc and pat0. The 4*4 third reference pattern of gray6 can be composed of pata and patb, or composed of pata and patc. The 4*4 fourth reference pattern of gray8 can be composed of patb or composed of patc. Therefore, step S1 can select the required unit pattern according to the reference pattern to be generated, and place the selected 4 unit patterns in the upper left, upper right, lower left, and lower right to obtain the reference pattern.

[0071] It should be noted that the carry pixels in the reference pattern are evenly distributed on both sides of the diagonal line.

[0072] In step S2, the transformation combination includes a first transformation combination, a second transformation combination and a third transformation combination; the first transformation combination is to interchange the left two columns and the right two columns of the reference pattern; the second transformation combination is to interchange the upper two rows and the lower two rows of the reference pattern; the third transformation combination (such as Figure 5 ) is to swap the diagonal lines of the lower right unit pattern with the diagonal lines of the upper left unit pattern of the reference pattern, and to swap the diagonal lines of the lower left unit pattern with the diagonal lines of the upper right unit pattern.

[0073] In step S2, as described in the previous example, for the first reference pattern of gray2, the components Figure 6 The first reference pattern shown (the upper left and lower right are both pata_0; the upper right and lower left are both pat0) is transformed and combined to obtain a multi-frame reference pattern, including:

[0074] Acquire an upper left unit pattern, an upper right unit pattern, a lower left unit pattern, and a lower right unit pattern in the composed first reference pattern;

[0075] The unit pattern in the lower right corner is replaced by other first-type unit patterns (pata_1, pata_2, pata_3) in turn to obtain the first reference patterns of the first row of three frames (such as Figure 7shown);

[0076] For the composed first reference pattern and the obtained three frames of first reference patterns, the following steps are performed: the upper left unit pattern is replaced with other first type unit patterns (pata_1, pata_2, pata_3) in turn, and a total of 12 frames of new first reference patterns (such as Figure 7 shown);

[0077] For the 16 frames of first reference patterns obtained, the following operations are performed: exchanging the upper left unit pattern with the upper right unit pattern, and exchanging the lower left unit pattern with the lower right unit pattern in the first reference pattern, to obtain 16 frames of new first reference patterns, and now a total of 32 frames of first reference patterns are obtained.

[0078] In order to ensure that the dither patterns with the number of carry pixels of 1, 2, and 3 are averaged in the time domain, the 32 frames of the first reference patterns are further processed as follows: Figure 8 Specifically, Figure 8 In the example, the rule is: the 32 frames of first reference patterns are arranged into two 4*4 matrices in the order in which they are obtained, the first first reference pattern is used as the reference pattern of frame 1, the reference pattern of frame 1 is subjected to the first transformation combination to generate the reference pattern of frame 2; the reference pattern of frame 2 is used as the reference pattern of frame 3, the reference pattern of frame 3 is subjected to the first transformation combination to generate the reference pattern of frame 4; in the second traversal, the 1+5*1 first reference pattern is used as frame 5 (i.e., along the first matrix) in the order in which the first reference pattern is obtained. Figure 7traverse in the diagonal direction shown), perform the first transformation combination on the reference pattern of frame5 to generate the reference pattern of frame6; use the reference pattern of frame6 as the reference pattern of frame7, perform the first transformation combination on the reference pattern of frame7, and generate the reference pattern of frame8; continue to traverse, select one of the 32 first reference patterns as the reference pattern of frame4k+1 (k∈[0,15]) in the above order, perform the first transformation combination on the reference pattern of frame4k+1, and generate the reference pattern of frame4k+2; use the reference pattern of frame4k+2 as the reference pattern of frame4k+3, perform the first transformation combination on the reference pattern of frame4k+3, and generate the reference pattern of frame4k+4. In this way, when k=15, 16 frames of first reference patterns have been traversed, and 64 frames of first reference patterns are obtained. For the remaining 16 frames of first reference patterns, continue to cycle according to the above method to obtain 64 frames of first reference patterns. In addition, for the obtained 64-frame first reference patterns, if the 2*2 unit patterns at the lower right position in frame1 and frame5, ..., frame(4k+1) and frame(4k+5)(k∈[0,15]) are exchanged, different 64-frame 4*4 first reference patterns can be obtained.

[0079] It should be noted that, for the second reference pattern of gray4 composed of patc and pat0, the method is similar to that of the first reference pattern of gray2, which will not be repeated here.

[0080] In step S2, as described in the previous example, for the components of patb and pat0, Fig. 9 The two gray4 second reference patterns shown (the upper left and lower right are the same patb; the upper right and lower left are pat0), in order to achieve the average of the carried pixels in the time domain, the two second reference patterns are transformed according to a certain rule to obtain Fig.10 8 frames of the second reference pattern. Fig.11 The two second reference patterns shown (the upper left and lower right are different patb, the upper right and lower left are both pat0), these two second reference patterns can be combined into Fig.12 8 frames of second reference patterns are shown.

[0081] In order to better average the carry points of a frame, choose a pata composed of Fig.13 In order to ensure that the dithering patterns with the number of carry pixels of 3, 4, and 5 reach the average of the carry points in the time domain, Fig.13 The four second reference patterns shown are Fig.14 Arrange in the manner shown. Fig.14In the example, the reference pattern of frame2 can be obtained by combining the reference pattern of frame1 through the second transformation, the reference pattern of frame3 can be obtained by combining the reference pattern of frame2 through the third transformation, and the reference pattern of frame4 can be obtained by combining the reference pattern of frame3 through the second transformation. The reference pattern of frame5 can be obtained by combining the reference pattern of frame1 through the third transformation, the reference pattern of frame9 can be obtained by combining the reference pattern of frame5 through the first transformation, and the reference pattern of frame13 can be obtained by combining the reference pattern of frame9 through the third transformation.

[0082] In step S2, as described in the previous example, the third reference pattern of gray6 can be composed of pata and patb. Group pata and patb according to Table 1, Fig.15 Frame1, frame5, frame9 and frame13 in the image are traversed according to the method in Table 1. The reference pattern of frame2 is obtained by combining the reference pattern of frame1 through the first transformation, the reference pattern of frame3 is obtained by combining the reference pattern of frame2 through the second transformation, and the reference pattern of frame4 is obtained by combining the reference pattern of frame3 through the first transformation. According to the above rules, we can get Fig.15 In addition, by exchanging patb_0 and patb_1, pata_0 and pata_1, pata_2 and pata_3, another 16 frames of third reference patterns can be obtained.

[0083] Table 1

[0084]

[0085] The third reference pattern of gray6 can be composed of pata_1 and patc_2. According to dividing pata into two groups: pata_0+pata_3 and pata_1+pata_2, patc is divided into two groups: patc_3+patc_2 and patc_0+patc_1, and arranged according to the preset arrangement method, the reference pattern of the second frame is obtained by transforming the reference pattern of the first frame according to the third transformation combination, and the reference pattern of the fourth frame is obtained by transforming the reference pattern of the third frame according to the first transformation combination. According to the above rules, it can be obtained Fig.16The third reference pattern of 32 frames 4*4 is shown. Preset arrangement: patc arrangement is patc_3+patc_2 in the first frame, patc_0+patc_1 in the fifth and ninth frames, patc_3+patc_2 in the thirteenth and seventeenth frames, patc_1+patc_0 in the twenty-first and twenty-fifth frames, and patc_3+patc_2 in the twenty-ninth frame; pata arrangement is pata_1+pata_2 in the first frame, pata_3+pata_0 in the fifth and ninth frames, pata_1+pata_2 in the thirteenth frame, pata_0+pata_3 in the seventeenth frame, pata_2+pata_1 in the twenty-first and twenty-fifth frames, and pata_0+pata_3 in the twenty-ninth frame.

[0086] In step S2, as described in the previous example, the fourth reference pattern of gray8 can be composed of patb. By combining patb_0 and patb_1, we can get Fig.17 By arranging these four fourth reference patterns according to the principle of average carry point, we can get Fig.18 The fourth reference pattern of gray8 can also be composed of patc. By combining patc_0, patc_1, patc_2, and patc_3, we can get Fig.19 According to the principle of average carry point, these four fourth reference patterns are arranged to obtain Fig. 20 The fourth reference pattern of 16 frames.

[0087] In the present invention, since the above four types of different reference patterns can be Figure 4 The unit pattern shown in the figure is composed of at least two generation modes for each gray scale, and the types of dithering patterns are more diverse and more flexible in application. Compared with storing 4*4 reference units in a frame n, the chip area occupied by storing dithering patterns is further reduced. Therefore, by storing unit patterns, multiple reference patterns can be flexibly obtained, and then the dithering pattern of each frame transformation is obtained based on the transformation and splicing of multiple reference patterns, which improves the application flexibility and thus improves the dithering effect.

[0088] In step S3, each frame of reference pattern is transformed and spliced ​​to obtain a transformed dither pattern for each frame, including the following three methods:

[0089] The first method: for each frame of reference pattern, the following steps are performed: using the reference pattern as the initial pattern of the first row and the first column, transforming the initial pattern according to a preset transformation rule to obtain patterns of each row and column;

[0090] The initial pattern and the transformed pattern are spliced ​​according to row and column positions to obtain the dithered pattern of the frame.

[0091] The second method: for each frame of reference pattern, the following operations are performed: using a logical NOT operator to perform an inversion operation on the reference pattern to obtain an initial pattern of the first row and the first column, and transforming the initial pattern according to a preset transformation rule to obtain patterns of each row and column;

[0092] The initial pattern and the transformed pattern are spliced ​​according to row and column positions to obtain a dithered pattern of the frame corresponding to the first category.

[0093] A third method is to alternate the dither pattern corresponding to the key category and / or the dither pattern corresponding to the first category between frames to obtain the dither pattern of the frame corresponding to the second category.

[0094] In a preferred embodiment, the preset transformation rule is:

[0095] The initial pattern is transformed according to a preset row transformation rule to obtain a pattern of the first row and second column, a pattern of the first row and third column, and a pattern of the first row and fourth column respectively;

[0096] Performing a third matrix transformation on the initial pattern to obtain a pattern in the second row and first column, and transforming the pattern in the second row and first column according to a preset row transformation rule to obtain a pattern in the second row and second column, a pattern in the second row and third column, and a pattern in the second row and fourth column, respectively;

[0097] Performing a second matrix transformation or a fourth matrix transformation on the pattern in the second row and first column to obtain a pattern in the third row and first column, and transforming the pattern in the third row and first column according to a preset row transformation rule to obtain a pattern in the third row and second column, a pattern in the third row and third column, and a pattern in the third row and fourth column, respectively;

[0098] Performing a third matrix transformation on the pattern in the third row and first column to obtain a pattern in the fourth row and first column, and transforming the pattern in the fourth row and first column according to a preset row transformation rule to obtain a pattern in the fourth row and second column, a pattern in the fourth row and third column, and a pattern in the fourth row and fourth column, respectively;

[0099] The initial pattern and the transformed pattern are spliced ​​according to row and column positions to obtain a dithered pattern;

[0100] Among them, the preset row transformation rule is to perform the first matrix transformation, the second matrix transformation, and the first matrix transformation in sequence; the first matrix transformation is to exchange the two adjacent rows in the matrix; the second matrix transformation is to exchange the upper two rows and the lower two rows of the matrix; the third matrix transformation is to exchange the two adjacent columns in the matrix; the fourth matrix transformation is to exchange the left two columns and the right two columns of the matrix.

[0101] Specifically, the first matrix transformation is as follows Fig.21 As shown, the 0th row is swapped with the 1st row, and the 2nd row is swapped with the 3rd row; the second matrix transformation is as follows Fig. 22 As shown, the 0th and 1st rows are swapped with the 2nd and 3rd rows; the third matrix transformation is as follows Fig.23 As shown, swap the 0th column with the 1st column, and swap the 2nd column with the 3rd column; the fourth matrix transformation is as follows Fig.24 As shown, swap columns 0 and 1 with columns 2 and 3. Figure 3 As shown, the preset transformation rules are as follows Fig.25 As shown, the first matrix transformation is represented as mode1, the second matrix transformation is represented as mode2, the third matrix transformation is represented as mode3, and the fourth matrix transformation is represented as mode4. It should be noted that, Figure 21 to Figure 24 In the figure, the left figures are schematic diagrams before transformation, and the right figures are schematic diagrams after transformation.

[0102] In the present invention, a symmetrical reference pattern is selected, and after transformation according to the above transformation method, the carry pixels in the reference pattern are traversed in the row direction and the column direction respectively. Therefore, for a dithering pattern with a size of 16*16, the proportions of the carry pixels in the units of 16*16, 4*4, 16*1, and 1*16 are the same, which can further improve the visual effect and achieve a better dithering effect.

[0103] In order to achieve the average between frames, the traditional FRC will store multiple frames of dithering patterns and perform periodic transformations in frames. The present invention does not need to store multiple frames of dithering patterns, and can flexibly generate multiple frames of dithering patterns based on the stored 11 unit patterns, thereby improving application flexibility.

[0104] like Fig.26 , Fig. 27 As shown, an embodiment of the present invention provides an inter-frame dithering pattern generation device in FRC. The device embodiment can be implemented by software, or by hardware or a combination of software and hardware. From the hardware level, Fig.26 FIG. 1 is a hardware architecture diagram of a computing device where an inter-frame dithering pattern generating device in an FRC according to an embodiment of the present invention is located. Fig. 27 In addition to the processor, memory, network interface, and non-volatile memory shown in the figure, the computing device in which the device is located in the embodiment may also generally include other hardware, such as a forwarding chip responsible for processing messages, etc. Taking software implementation as an example, Fig. 27 As shown, as a device in a logical sense, the CPU of the computing device in which it is located reads the corresponding computer program in the non-volatile memory into the internal memory and runs it. This embodiment provides a device for generating an inter-frame dithering pattern in FRC, including:

[0105] A color depth difference determination module 270, for determining a color depth difference between a color depth to be displayed and a color depth of a display screen; wherein the color depth to be displayed is higher than the color depth;

[0106] A dither pattern determination module 272, for determining the size and type of the dither pattern according to the color depth difference, and filtering out key types from the types;

[0107] The processing module 274 is used to divide the dither pattern corresponding to each key category according to the color depth difference to obtain a plurality of basic patterns; and determine a reference pattern from the basic patterns, divide the reference pattern to obtain a plurality of unit patterns, and obtain the dither pattern of each frame by transforming and splicing the unit patterns; wherein the number of the reference patterns is the same as the number of the key categories.

[0108] In some specific implementations, the color depth difference determination module 270 may be used to execute the above step 200 , the dither pattern determination module 272 may be used to execute the above step 202 ; and the processing module 274 may be used to execute the above steps 204 and 206 .

[0109] In some specific implementations, the dither pattern determination module 272 is further configured to perform the following operations:

[0110] The size of the dither pattern is determined according to the color depth difference; wherein the size is n 2 *n 2 ; n is the color depth difference;

[0111] The type and number of dither patterns are determined according to the size; the ratio of the number of carry pixels to the number of non-carry pixels in different types is different, and the number of types is n. 2 -1.

[0112] In some specific implementations, the dither pattern determination module 272 is further configured to perform the following operations:

[0113] A two-dimensional binary matrix is ​​used to represent the dithering pattern; wherein the size of the two-dimensional binary matrix is ​​the same as the size; when the matrix element value of the two-dimensional binary matrix is ​​1, it represents a carry pixel, and when the matrix element value is 0, it represents a non-carry pixel;

[0114] Filter out key categories from the categories, including:

[0115] A binary code is used to represent the number of carry pixels in a two-dimensional binary matrix;

[0116] The actual values ​​corresponding to the binary codes whose least significant bits are even are sorted from small to large, and the types of dithering patterns represented by the two-dimensional binary matrices corresponding to the first n binary codes are used as key types; n is the color depth difference;

[0117] The two-dimensional binary matrix of the dither pattern corresponding to the key category is inverted by using a logical NOT operator to obtain a two-dimensional binary matrix of the dither pattern corresponding to the first category; the dither pattern corresponding to the binary code whose least significant bit is an even number is alternately displayed between frames to obtain a dither pattern corresponding to the binary code whose least significant bit is an odd number corresponding to the second category; wherein the category consists of the key category, the first category and the second category.

[0118] In some specific implementations, the processing module 274 is further configured to perform the following operations:

[0119] According to the color depth difference, the size of the basic pattern is determined; wherein the size of the basic pattern is n*n; n is the color depth difference;

[0120] According to the size of the basic pattern, the dither pattern corresponding to the key category is divided in order from left to right and from top to bottom to obtain n 2 A basic pattern.

[0121] In some specific embodiments, the size of the unit pattern is 2*2; the reference pattern includes at least two unit patterns; wherein, 4 types of unit patterns are included, and the number of carry pixels in the same type of unit patterns is the same, and the positions of carry pixels in different unit patterns are different.

[0122] In some specific implementations, when the color depth difference is 4, the processing module 274 is further configured to perform the following operations:

[0123] Select a reference pattern consisting of 4 unit patterns;

[0124] Transforming and combining the composed reference patterns to obtain multiple frames of reference patterns;

[0125] The reference pattern of each frame is transformed and spliced ​​to obtain the transformed dithered pattern of each frame.

[0126] In some specific implementations, when the color depth difference is 4, the processing module 274 is further configured to perform the following operations:

[0127] For each frame of reference pattern, execute:

[0128] The reference pattern is used as the initial pattern of the first row and the first column, and the initial pattern is transformed according to a preset transformation rule to obtain patterns of each row and column;

[0129] The initial pattern and the transformed pattern are spliced ​​according to row and column positions to obtain the dithered color pattern of the frame;

[0130] and / or,

[0131] Using a logical NOT operator to perform an inversion operation on the reference pattern to obtain an initial pattern of the first row and the first column, and transforming the initial pattern according to a preset transformation rule to obtain patterns of each row and column;

[0132] The initial pattern and the transformed pattern are spliced ​​according to row and column positions to obtain the dithered pattern of the frame.

[0133] In some specific implementations, the preset transformation rule is:

[0134] The initial pattern is transformed according to a preset row transformation rule to obtain a pattern of the first row and second column, a pattern of the first row and third column, and a pattern of the first row and fourth column respectively;

[0135] Performing a third matrix transformation on the initial pattern to obtain a pattern in the second row and first column, and transforming the pattern in the second row and first column according to a preset row transformation rule to obtain a pattern in the second row and second column, a pattern in the second row and third column, and a pattern in the second row and fourth column, respectively;

[0136] Performing a second matrix transformation or a fourth matrix transformation on the pattern in the second row and first column to obtain a pattern in the third row and first column, and transforming the pattern in the third row and first column according to a preset row transformation rule to obtain a pattern in the third row and second column, a pattern in the third row and third column, and a pattern in the third row and fourth column, respectively;

[0137] Performing a third matrix transformation on the pattern in the third row and first column to obtain a pattern in the fourth row and first column, and transforming the pattern in the fourth row and first column according to a preset row transformation rule to obtain a pattern in the fourth row and second column, a pattern in the fourth row and third column, and a pattern in the fourth row and fourth column, respectively;

[0138] The initial pattern and the transformed pattern are spliced ​​according to row and column positions to obtain a dithered pattern;

[0139] Among them, the preset row transformation rule is to perform the first matrix transformation, the second matrix transformation, and the first matrix transformation in sequence; the first matrix transformation is to exchange the two adjacent rows in the matrix; the second matrix transformation is to exchange the upper two rows and the lower two rows of the matrix; the third matrix transformation is to exchange the two adjacent columns in the matrix; the fourth matrix transformation is to exchange the left two columns and the right two columns of the matrix.

[0140] It is to be understood that the structure illustrated in the embodiment of the present invention does not constitute a specific limitation on an inter-frame dither pattern generating device in an FRC. In other embodiments of the present invention, an inter-frame dither pattern generating device in an FRC may include more or fewer components than shown in the figure, or combine some components, or separate some components, or arrange the components differently. The components shown in the figure may be implemented in hardware, software, or a combination of software and hardware.

[0141] The information interaction, execution process and other contents between the modules in the above-mentioned device are based on the same concept as the embodiment of the method of the present invention. For the specific contents, please refer to the description in the embodiment of the method of the present invention, and no further description is given here.

[0142] An embodiment of the present invention further provides a computing device, including a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, a method for generating an inter-frame dithering pattern in an FRC in any embodiment of the present invention is implemented.

[0143] An embodiment of the present invention further provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the processor executes a method for generating an inter-frame dithering pattern in an FRC according to any embodiment of the present invention.

[0144] An embodiment of the present application further provides a computer program product, which includes a computer program. A processor of a computer device reads the computer program from a computer-readable storage medium, and the processor executes the computer program, so that the computer device executes the method for generating an inter-frame dithering pattern in an FRC as described in any of the above embodiments.

[0145] Specifically, a system or device equipped with a storage medium can be provided, on which software program code that implements the functions of any of the above-mentioned embodiments is stored, and a computer (or CPU or MPU) of the system or device can be enabled to read and execute the program code stored in the storage medium.

[0146] In this case, the program code itself read from the storage medium can realize the function of any one of the above-mentioned embodiments, and thus the program code and the storage medium storing the program code constitute a part of the present invention.

[0147] The storage medium embodiments for providing the program code include a floppy disk, a hard disk, a magneto-optical disk, an optical disk (such as CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-RAM, DVD-RW, DVD+RW), a magnetic tape, a non-volatile memory card, and a ROM. Alternatively, the program code can be downloaded from a server computer by a communication network.

[0148] In addition, it should be clear that the functions of any of the above embodiments can be implemented not only by executing the program code read by the computer, but also by enabling an operating system operating on the computer to complete part or all of the actual operations based on instructions from the program code.

[0149] In addition, it can be understood that the program code read from the storage medium is written to a memory provided in an expansion board inserted into the computer or to a memory provided in an expansion module connected to the computer, and then based on the instructions of the program code, a CPU installed on the expansion board or expansion module is enabled to perform part or all of the actual operations, thereby realizing the functions of any of the above-mentioned embodiments.

[0150] It should be noted that, in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the statement "comprise a ..." do not exclude the presence of other identical factors in the process, method, article or device including the elements.

[0151] A person of ordinary skill in the art can understand that all or part of the steps of implementing the above method embodiments can be completed by hardware related to program instructions, and the aforementioned program can be stored in a computer-readable storage medium. When the program is executed, it executes the steps of the above method embodiments; and the aforementioned storage medium includes: ROM, RAM, magnetic disk or optical disk, etc., various media that can store program codes.

[0152] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for generating an inter-frame dithering pattern in FRC, characterized in that: include: Determining a color depth difference between a color depth to be displayed and a color depth of a display screen; wherein the color depth to be displayed is higher than the color depth; Determining the size and type of the dither pattern according to the color depth difference, and selecting key types from the types; Dividing the dither pattern corresponding to each of the key categories according to the color depth difference to obtain a plurality of basic patterns; A reference pattern is determined from the basic pattern, and the reference pattern is divided to obtain a plurality of unit patterns, so as to obtain a dithered pattern that changes in each frame by transforming and splicing the unit patterns; wherein the number of the reference patterns is the same as the number of the key types.

2. The method according to claim 1, characterized in that The step of determining the size and type of the dither pattern according to the color depth difference includes: The size of the dither pattern is determined according to the color depth difference; wherein the size is n 2 *n 2 ; n is the color depth difference; The type and number of the dither pattern are determined according to the size; wherein the ratio of the number of carry pixels to the number of non-carry pixels in different types is different, and the number of types is n. 2 -1; and / or, Divide the dither pattern corresponding to each key category according to the color depth difference to obtain several basic patterns, including: According to the color depth difference, determine the size of the basic pattern; wherein the size of the basic pattern is n*n; n is the color depth difference; According to the size of the basic pattern, the dither pattern corresponding to the key type is divided in order from left to right and from top to bottom to obtain n 2 The basic pattern.

3. The method according to claim 1, characterized in that The dither pattern is represented by a two-dimensional binary matrix; wherein the size of the two-dimensional binary matrix is ​​the same as the size; when the matrix element value of the two-dimensional binary matrix is ​​1, it represents a carry pixel, and when the matrix element value is 0, it represents a non-carry pixel; The key categories are screened out from the categories, including: Using binary code to represent the number of carry pixels in the two-dimensional binary matrix; The actual values ​​corresponding to the binary codes whose least significant bits are even are sorted from small to large, and the types of dithering patterns represented by the two-dimensional binary matrices corresponding to the first n binary codes are used as the key types; n is the color depth difference; The two-dimensional binary matrix of the dither pattern corresponding to the key category is inverted using a logical NOT operator to obtain a two-dimensional binary matrix of the dither pattern corresponding to the first category; the dither pattern corresponding to the binary code whose least significant bit is an even number is alternately displayed between frames to obtain a dither pattern corresponding to the binary code whose least significant bit is an odd number corresponding to the second category; wherein the categories consist of the key category, the first category, and the second category.

4. The method according to claim 3, characterized in that The size of the unit pattern is 2*2; the reference pattern includes at least two of the unit patterns; wherein, the unit patterns include 4 types, and the number of carry pixels in the unit patterns of the same type is the same, and the positions of carry pixels of different unit patterns are different.

5. The method according to claim 4, characterized in that When the color depth difference is 4, the dithering pattern that changes in each frame is obtained by transforming and splicing the unit patterns, including: Selecting a reference pattern consisting of four of the unit patterns; Transforming and combining the composed reference patterns to obtain multiple frames of reference patterns; The reference pattern of each frame is transformed and spliced ​​to obtain the dithered pattern of each frame.

6. The method according to claim 5, characterized in that The step of transforming and splicing the reference pattern of each frame to obtain the transformed dither pattern of each frame includes: For each frame of the reference pattern, the following steps are performed: Using the reference pattern as the initial pattern of the first row and the first column, transforming the initial pattern according to a preset transformation rule to obtain patterns of each row and column; splicing the initial pattern and the transformed pattern according to row and column positions to obtain a dithered pattern of the frame; and / or, Using a logical NOT operator to perform an inversion operation on the reference pattern to obtain an initial pattern of the first row and the first column, and transforming the initial pattern according to a preset transformation rule to obtain patterns of each row and column; The initial pattern and the transformed pattern are spliced ​​according to row and column positions to obtain the dithered pattern of the frame.

7. The method according to claim 6, characterized in that The preset transformation rule is: Transforming the initial pattern according to a preset row transformation rule to obtain a pattern of the first row and second column, a pattern of the first row and third column, and a pattern of the first row and fourth column respectively; Performing a third matrix transformation on the initial pattern to obtain a pattern in the second row and first column, and transforming the pattern in the second row and first column according to the preset row transformation rule to obtain a pattern in the second row and second column, a pattern in the second row and third column, and a pattern in the second row and fourth column, respectively; Performing a second matrix transformation or a fourth matrix transformation on the pattern in the second row and first column to obtain a pattern in the third row and first column, and transforming the pattern in the third row and first column according to the preset row transformation rule to obtain a pattern in the third row and second column, a pattern in the third row and third column, and a pattern in the third row and fourth column, respectively; Performing a third matrix transformation on the pattern in the third row and first column to obtain a pattern in the fourth row and first column, and transforming the pattern in the fourth row and first column according to the preset row transformation rule to obtain a pattern in the fourth row and second column, a pattern in the fourth row and third column, and a pattern in the fourth row and fourth column, respectively; splicing the initial pattern and the transformed pattern according to row and column positions to obtain the dithered pattern; Among them, the preset row transformation rule is to perform the first matrix transformation, the second matrix transformation, and the first matrix transformation in sequence; the first matrix transformation is to exchange the two adjacent rows in the matrix; the second matrix transformation is to exchange the upper two rows and the lower two rows of the matrix; the third matrix transformation is to exchange the two adjacent columns in the matrix; the fourth matrix transformation is to exchange the left two columns and the right two columns of the matrix.

8. An inter-frame dithering pattern generating device in FRC, characterized in that: include: A color depth difference determination module, used to determine the color depth difference between the color depth to be displayed and the color depth of the display screen; wherein the color depth to be displayed is higher than the color depth; a dither pattern determination module, configured to determine the size and type of the dither pattern according to the color depth difference, and select key types from the types; A processing module is used to divide the dither pattern corresponding to each of the key categories according to the color depth difference to obtain a plurality of basic patterns; and determine a reference pattern from the basic patterns, divide the reference pattern to obtain a plurality of unit patterns, so as to obtain a dither pattern that changes in each frame by transforming and splicing the unit patterns; wherein the number of the reference patterns is the same as the number of the key categories.

9. A computing device, comprising a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the method according to any one of claims 1 to 7 is implemented.

10. A computer-readable storage medium having a computer program stored thereon, which, when executed in a computer, causes the computer to execute the method according to any one of claims 1 to 7.

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