JPH0883330A - Signal conversion method and signal conversion device - Google Patents

Abstract

(57) [Summary] [Object] To provide a highly accurate signal conversion method and a highly accurate and low cost signal conversion device with a simple configuration. [Structure] Unit cubes ABCDEFGH and EFGHIJ
If the body center points of KL are P and Q, octahedron EF
Cut out GHQP and add four tetrahedra FEQP and FG
It is divided into QP, HGQP and HEQP. According to the present invention, two body-centered lattice points of two unit cubes adjacent to each other and the two
It is divided into tetrahedrons having two basic lattice points located at the boundary of one unit cube and adjacent to each other as vertices, and the data in the tetrahedron is a converted signal obtained by interpolating the data of the four vertices. can get.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color signal converting device for converting a color signal such as a color printer, a color copying machine, a color scanner, a coordinate for converting a coordinate signal in three-dimensional graphics or a three-dimensional CAD. The present invention relates to a signal conversion method and a signal conversion device that convert three input signals into a single output signal, such as a signal conversion device.

[0002]

2. Description of the Related Art Conventionally, as in a color image signal, 3
When the conversion from one input signal to one output signal is complicated, a signal conversion method using a three-dimensional table method is known. However, for example, three input signals X, Y,
If the value of Z is 241 in the range of 0 to 240, the conversion signal requires a table having 241 ³ = 13997521 pieces of data, which is not practical because the storage means is expensive.

Therefore, in order to reduce the amount of data in the storage means, there is a signal conversion method using a three-dimensional table interpolation method as shown in FIG. In this method, a large cube having the values of three input signals X, Y and Z as orthogonal axes is formed,
A large cube is divided into a predetermined size, that is, a unit cube, and a unit cube ABCDEF containing a converted signal to be obtained.
The GH is cut out and the data of the lattice points are interpolated to obtain a converted signal. For example, assuming that the grid points of the three input signals X, Y, and Z have 16 levels of 0, 16, 32, ..., 240, respectively, if 16 ³ = 4096 data are prepared to obtain the converted signal. This is good, and the data amount is about 1/3400 as compared with the three-dimensional table method.

In this method, there are various interpolation methods depending on the number of grid points, but the smaller the number of grid points used for interpolation, the smaller the scale of the hardware such as the interpolation processing means. Therefore, as shown in FIG. The four of five
Japanese Unexamined Patent Publication No. 53-123201 discloses a method of performing interpolation processing from data of four grid points divided into a surface.

In FIG. 12, a point to be interpolated is a tetrahedron A.
It is determined which of BCG, ABDE, BEFG, DEHG, and BDEG is included, and the data of the converted signal is obtained by linearly interpolating the data of the four vertices of the determined tetrahedron.

[0006]

In such a signal conversion method, four outer tetrahedrons ABDE, ABCG, and BE are used.
The volume of FG and DEGH is 1/6 of the unit cube, whereas the volume of the central tetrahedron ABDE is 3 of the unit cube.
The difference between the long sides and the short sides of the four outer tetrahedrons is large. Due to such a geometrical bias, the above-mentioned division method has a problem that the error of the converted signal is large.

Further, in order to realize high-speed processing of such a signal conversion method by a digital circuit, it is necessary to read data of four different grid points at the same time, so four storage means for storing data of grid points are required. there were. It is inefficient to have four storage means for the data of grid points with the same contents,
The accuracy of the converted signal was not good for the size of the storage means as a whole.

The present invention has been made in view of the above problems, and a tetrahedron division method having no geometrical bias provides
It is an object of the present invention to provide a signal conversion method in which the accuracy of a converted signal is good and variation in signal accuracy among regions of a tetrahedron is small.

It is another object of the present invention to provide a signal conversion device which uses the two types of grid point storage means and interpolating means in the above method and has less variation in signal accuracy among regions of a tetrahedron.

It is another object of the present invention to provide a low-cost signal conversion device using the four types of grid point storage means and interpolating means in the above method, with less variation in signal accuracy among regions of a tetrahedron.

[0011]

In order to achieve the above object, the signal conversion method of the present invention interpolates data of lattice points of a body-centered cubic lattice composed of upper bits of three input signals. A signal conversion method for obtaining an output signal, comprising:
Two body-centered lattice points of two unit cubes that are adjacent to each other and the two body-centered lattice points that are located at the boundary between the two unit cubes and are adjacent to each other 2
The structure is divided into tetrahedrons each having one basic lattice point as a vertex, and the data in the tetrahedron is subjected to interpolation processing of the data of the four vertices.

Further, the signal conversion apparatus of the present invention is a signal conversion apparatus for interpolating data of lattice points of a body-centered cubic lattice composed of upper bits of three input signals to obtain an output signal, It is divided into tetrahedrons having two body center points of two adjacent unit cubes and two basic lattice points adjacent to each other located at the boundary between the two unit cubes as vertices,
Tetrahedral discriminating means for discriminating in which of the tetrahedrons the three input signals exist, address generating means for generating an address of the vertex of the discriminated tetrahedron, and data of basic lattice points are stored. Basic grid point data storage means,
Body-centered grid point data storage means for storing body-centered grid point data, weighting coefficient calculation means for calculating a weighting coefficient of the apex for interpolating data in the determined tetrahedron, and basic data The interpolation means is configured to perform the interpolation process based on the two vertex data from the storage means and the body-core data storage means and the weighting coefficient from the weighting coefficient calculating means.

Further, in the signal conversion apparatus of the present invention, in the configuration of the first embodiment, the basic lattice point data storage means stores even basic lattice point data storage means for storing data of even-numbered basic lattice points, The odd-numbered basic lattice point data storage means stores the data of the odd-numbered basic lattice points, and the body-centered lattice point data interpolating means stores the even-numbered body-centered lattice point data storage means. And an odd-numbered body-centered lattice point data storage unit that stores data of odd-numbered body-centered lattice points. However, the coordinates of the basic lattice point and the body-centered lattice point are (l, m, n), (l-0.
5, m-0.5, n-0.5) {l, m, n: integer}, where l + m + n is an even number and l + m + n is an odd number.

[0014]

With the above construction, since the size and shape of the tetrahedron are not biased, a highly accurate converted signal can be obtained.

Further, the basic data storage means and the body-centered data storage means make it possible to obtain a highly accurate signal conversion device without increasing the cost.

Further, the even-numbered basic data storage means, the odd-numbered basic data storage means, the even-numbered body-centered data storage means, and the odd-numbered body-centered data storage means make it possible to obtain a highly accurate signal conversion device at a lower cost than ever before.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIG.
From now on, description will be made with reference to FIG.

FIG. 1 is a diagram showing the principle of tetrahedron division of a signal conversion apparatus according to the first embodiment of the present invention, which is a unit cube ABCD in the three-dimensional table interpolation method described in the prior art.
EFGH and its adjacent unit cube, EFGHIJKL
think of. In Fig. 1, the unit cube ABCDEFGH
Letting P and Q be the body center points of EFGHIJKL and EFGHIJKL, the octahedron EFGHQ is cut out and further divided into four tetrahedra FEQP, FGQP, HGQP, and HEQP. The present invention divides into two tetrahedrons having two body-centered lattice points of two unit cubes adjacent to each other and two basic lattice points adjacent to each other located at the boundary between the two unit cubes as vertices, The data in the body is obtained by interpolating the data of the four vertices.

In FIG. 1, a unit cube EFGHIJKL is formed on the unit cube ABCDEFGH and is adjacent to the unit cube.
Considering the face piece EFGHQP, in reality, as shown in FIG.
As shown in (b) and (c), the six 8
Face piece ABCDRP, EFGHQP, ADHESP, BC
GFTP, ABFEUP, CDHGVP exist, and each octahedron is divided into four, totaling 24 tetrahedra AB
RP, CBRP, CDRP, ADRP, FEQP, FG
QP, HGQP, HEQP, ADSP, HDSP, HE
SP, AESP, CBTP, CGTP, FGTP, FB
TP, ABUP, FBUP, FEUP, AEUP, CD
There are VP, CGVP, HGVP and HDVP.

All points in the unit cube ABCDEFGH belong to one of the above 24 tetrahedra. This division method has a smaller tetrahedron size (one-twelfth the volume of a unit cube) than the conventional tetrahedron division method of FIG.
Moreover, since the size and shape are all the same, the accuracy of the converted signal is good, and the accuracy does not vary from region to region.

FIG. 3 is a block diagram of a signal conversion apparatus according to the first embodiment of the present invention. It identifies which tetrahedron the point to be obtained by the tetrahedron judging means 2 belongs to, and the table address generating means. The coordinates of the vertices of the tetrahedron specified in 3 are calculated and converted into the addresses of the basic lattice point data storage means 4 and the body center lattice point data storage means 5. The basic lattice point data storage means 4 and the body-centered lattice point data storage means 5 output the data of the vertices of the tetrahedron from the address signal. The weighting factor calculation means 6 calculates the weighting factor of the vertex of the specified tetrahedron for generating the data of the point to be interpolated. The interpolation means 7 is 4
Interpolation processing is performed on the data DA of the vertex of the face piece and the data DA to be obtained from the weighting coefficient.

The configuration and operation of the signal conversion device 1 will be described in detail below. In FIG. 3, the three 8-bit input signals X, Y, Z are the upper 4-bit signals X ', Y',
Z'and lower 4-bit signals x, y, z are input to the lower-order bit signals x, y, z to the tetrahedron determining means 2, and upper 4-bit signals X ', Y', Z'are address generating means. Input to 3. In the present invention, for convenience of description, the input signal is a fixed-point number, and the upper 4 bits are the integer part and the lower 4 bits.
The bit is the minority part.

The tetrahedron judging means 2 judges whether the point to be obtained in the unit cube belongs to any of the 24 tetrahedrons, and the lower 4 bit signals x, y, shown in (Table 1).
Six relational expressions of z y−x, y + x−1, z−x, z + x
It is determined whether -1, z-y, and z + y-1 are positive (+) or negative (-), and the determination result is a 5-bit tetrahedral determination signal T.
It is output as E together with the lower 4 bit signals x, y, z. However, when the value of the relational expression is 0, it does not matter which is determined, but here, it is positive (+).

[0024]

[Table 1]

The address generating means 3 uses the upper 4-bit signals X ', Y', Z'of the input signal and the tetrahedron determination signal TE to output 4 bits.
It outputs the table address corresponding to the coordinates of the four tetrahedra.

[0026]

[Table 2]

[0027]

[Table 3]

The four grid point addresses of the tetrahedron are composed of two basic grid point addresses AD0 and AD1 and two body-centered grid point addresses AD2 and AD3, and are shown in (Table 2) according to the tetrahedron determination signal TE. It becomes the address of the grid point. The lattice point address is four values X ″ n, Y ″ n, Z ″ n (n = 0) generated by the operations shown in (Table 3) of the upper 4 bits X ′, Y ′, Z ′ of the input signal. 1, 2, 3).

By the above-described processing, basic grid point addresses AD0 and AD1 and body-centered grid point addresses AD2 and AD3 are generated, and two basic grid point data storage means 4 are provided.
And two body-centered lattice point data storage means 5.

The basic lattice point data storage means 4 and the body-centered lattice point data storage means 5 are composed of semiconductor memories, and when address signals AD0, AD1, AD2, AD3 are input, data DA0, DA1 corresponding to the addresses are input. DA2, DA3
Is read. The data of the basic lattice point data storage means 4 and the body-centered lattice point data storage means 5 are shown in FIG.
The data of the grid points shown in are stored. The basic grid point addresses AD0 and AD1 correspond to the coordinates of the basic grid point as they are, but the body-centered grid point addresses AD2 and AD3 have a value obtained by adding 0.5 to the coordinates X, Y, and Z of the body-centered grid point. . Basic lattice point data storage means 3 and body-centered lattice point data storage means 4
The output signals DA0, DA1, DA2, DA3 from are the values of the vertices of the tetrahedron and are sent to the interpolation means 7.

The weighting factor calculating means 6 is a tetrahedron judging signal TE from the tetrahedron judging means 2 and lower 4 bit signals x, y, z.
Required from.

For example, the coefficient when the tetrahedron is judged to be ABRP will be calculated. As shown in FIG. 5, the coordinates of the vertices of A, B, R, and P are (0,0,0), (1,0,0),
(0.5, 0.5, -0.5), (0.5, 0.5,
0.5). Since the inside of the tetrahedron can be linearly interpolated,
The value DA of the internal point (x, y, z) to be obtained is the function f (x,
y, z), a three-variable linear function

[0033]

[Equation 1]

It can be represented by Here, a, b, c, d are constants. The values of the vertices A, B, R and P of the tetrahedron are shown in FIG.
, DA0, DA1, DA2, DA3, respectively, and their respective weighting factors are WH0, WH1, WH2, W
If H3, the value DA of the point inside the tetrahedron can be expressed by (Equation 2).

[0035]

[Equation 2]

Substituting the coordinates and values of the vertices of the tetrahedron into (Equation 1) yields (Equation 3) to Equation 6.

[0037]

[Equation 3]

[0038]

[Equation 4]

[0039]

(Equation 5)

[0040]

(Equation 6)

When this is solved for a, b, c and d, it becomes (Equation 7) to (Equation 10).

[0042]

(Equation 7)

[0043]

[Equation 8]

[0044]

[Equation 9]

[0045]

[Equation 10]

Therefore, (Equation 1) is

[0047]

[Equation 11]

When this is arranged for DA0, DA1, DA2, DA3,

[0049]

[Equation 12]

From the correspondence with (Equation 2), the weighting factor W
H0, WH1, WH2, and WH3 are (Equation 13) to (Equation 16), respectively.

[0051]

[Equation 13]

[0052]

[Equation 14]

[0053]

[Equation 15]

[0054]

[Equation 16]

Although the above example is a coefficient when the tetrahedron is ABRP, it can be similarly obtained for other tetrahedrons. The results are shown in (Table 4). Weighting factor calculation means 6
Outputs four weighting factors WH0, WH1, WH2, WH3 to the interpolation means 7.

[0056]

[Table 4]

The interpolation processing means 7 includes vertex data DA0, DA1, DA2, DA3 from the two basic lattice point data storage means 4 and the two body-centered lattice point data interpolation storage means 5 and a weighting coefficient from the weighting coefficient calculating means 6. WH0, WH1, WH2, WH3
The sum of products operation shown in (Equation 2) is performed. FIG. 6 shows the interpolation means 7
The structure of the above is shown.
The product is obtained by one of the multipliers 8, the products are summed by the adder 9, the data inside the tetrahedron is interpolated, and the converted signal DA is output.

This completes the first embodiment of the present invention. 7 to 10 showing a second embodiment in which the capacity of the data storage means is reduced by improving the first embodiment of the present invention.
Will be described with reference to. The method of dividing the tetrahedron of the second embodiment is the same as that of the first embodiment, and therefore its explanation is omitted.

FIG. 7 is a block diagram of a signal conversion apparatus according to the second embodiment of the present invention, which tetrahedron determining means 2 specifies which tetrahedron the point to be obtained belongs to, and the even-odd address generating means 11 is specified. Then, the coordinates of the vertices of the tetrahedron are calculated, and the even basic lattice point data storage means 12 and the odd basic lattice point data storage means 1 are calculated.
3. Output addresses to the even-body-centered lattice point data storage means 14 and the odd-body-centered lattice point data storage means 14. The even-numbered basic lattice point data storage means 12, the odd-numbered basic lattice point data storage means 13, the body-centered lattice point data storage means 14 and the body-centered lattice point data storage means 15 output the data of the vertices of the tetrahedron from the address signal. Even-odd weight coefficient calculating means 16
Is the specified 4 for generating the data of the points to be interpolated.
The weighting factor of the vertex of the face piece is calculated. The interpolation processing means 6 is 4
Interpolation processing is performed on the data of the vertex of the face piece and the data DT of the point to be obtained from the weighting coefficient. Hereinafter, the configuration and operation of the signal conversion device 10 will be described in detail.

In FIG. 7, the tetrahedron determining means 2 has the same configuration as that of the first embodiment and outputs a tetrahedron determining signal TE together with the lower 4 bits x, y and z.

FIG. 8 is a block diagram of the even / odd address generating means of the signal converting apparatus according to the second embodiment of the present invention, in which the address generating means 2 having the same structure as that of the first embodiment is used. One basic lattice point address AD0, AD1 and two body-centered lattice point address AD2, AD3 are generated.

Now, the coordinates of the basic lattice point and the body-centered lattice point are (l, m, n), (l-0.5, m-0.5, n), respectively.
-0.5) {l, m, n: integer}, where even points are given when l + m + n is an even number, and odd points are given when l + m + n is an odd number. In FIG. 2, when the point A is an even number, the basic lattice point C,
F, H and body-centered grid points R, Q, S, T, U, V become even points, and basic grid points B, D, E, G and body-centered grid point P become odd points. When the point A is an odd number, the basic lattice point C,
F and H and body-centered grid points R, Q, S, T, U, and V are odd points, and basic grid points B, D, E, and G and body-centered grid point P are even points. In this way, depending on whether the point A is an even point or an odd point, it is determined whether each point is an even point or an odd point.

Therefore, the even / odd discrimination means 17 of FIG. 8 determines whether the point A is an even point or an odd point, as shown in (Table 5), the least significant bit of each of the upper 4 bit signals X ', Y', Z '. X '
Discrimination is made according to the values of 0, Y'0, Z'0, and 0 is output as an even-odd determination signal EO when the point A is an even point and 1 when it is an odd point.

[0064]

[Table 5]

The even / odd address conversion means 18 of FIG. 8 sends an address signal to the even basic grid point data storage means 12, the odd basic grid point data storage means 13, the body center grid point data storage means 14 and the body center grid point data storage means 15. AR0, AR
1, AR2, AR3 are generated. As shown in (Table 6), two basic grid point addresses AD0, AD1 and two body-centered grid point addresses AD2, AD3 from the table address generation unit 3 are generated. The least significant bit is discarded, and the even / odd determination signal EO from the even / odd determination means 17 performs an exchange process in the four multiplexers 19 to generate an address signal AR0,
AR1, AR2 and AR3 are generated.

[0066]

[Table 6]

FIG. 9 shows an even basic lattice point data storage means 1.
2. Odd basic lattice point data storage means 13, body-centered lattice point data storage means 14 and body-centered lattice point data storage means 15
The predetermined grid point data is stored in each storage means, and the even-odd address conversion means 18 outputs the four vertices necessary for interpolation processing by the address signals AR0, AR1, AR2, and AR3. Data DT0, DT1, DT
2, DT3 is output.

FIG. 10 shows the structure of the even-odd weighting coefficient calculating means 16, which has the same structure as that of the first embodiment. The weighting coefficient calculating means 6 is a tetrahedron judging signal TE from the tetrahedron judging means 2. And weighting factors WH0, WH1, WH2, WH3 from the lower 4 bit signals x, y, z, and the weighting factor exchange means 20 responds to the evenness / odd determination signal EO from the even / odd address generation means 11 with the weighting factors WH0, WH1, WH2 and WH3 are subjected to the exchange processing shown in (Table 7) by the four multiplexers 19 and the exchange-processed weighting factors WT0, WT1, WT
2, WT3 is output to the interpolation means 7.

[0069]

[Table 7]

The interpolating means 8 of FIG. 7 has the same configuration as that of the first embodiment, and has an even-numbered basic lattice point data storage means 12, an odd-numbered basic lattice point data storage means 13, a body-centered lattice point data storage means 14 and a body. The vertex data DT0, DT1, DT2, DT3 from the respective heart lattice point data storage means 15 and the weighting coefficients WT0, WT1, from the even-odd weighting coefficient calculating means 16
WT2 and WT3 are subjected to sum-of-products calculation as in (Equation 17), and the converted signal DT is output.

[0071]

[Equation 17]

Although the above two embodiments show the hardware configuration, they can be implemented by software using a general-purpose CPU or DSP. Further, the method of the present invention can be implemented by sharing both hardware and software.

[0073]

As is apparent from the above embodiments, according to the present invention, it is possible to realize an excellent signal conversion device capable of performing highly accurate three-dimensional signal conversion at low cost with a simple structure. Is.

[Brief description of drawings]

FIG. 1 is a principle diagram of tetrahedron division of a signal conversion device according to a first embodiment of the present invention.

FIG. 2 is a principle diagram of tetrahedron division of the signal conversion device according to the first embodiment of the present invention.

FIG. 3 is a configuration diagram of a signal conversion device according to a first embodiment of the present invention.

FIG. 4 is an explanatory diagram of grid point data of the signal conversion device according to the first embodiment of the present invention.

FIG. 5 is an explanatory diagram of a signal conversion device according to the first embodiment of the present invention.

FIG. 6 is a configuration diagram of an interpolating means of the signal converting apparatus according to the first embodiment of the present invention.

FIG. 7 is a block diagram of a signal conversion device according to a second embodiment of the present invention.

FIG. 8 is a configuration diagram of an even-odd address generating means of the signal conversion device according to the second embodiment of the present invention.

FIG. 9 is an explanatory diagram of grid point data of the signal conversion device according to the second embodiment of the present invention.

FIG. 10 is a configuration diagram of an even-odd weight coefficient calculating means of a signal conversion device according to a second embodiment of the present invention.

FIG. 11 is a principle diagram of a conventional table interpolation method.

FIG. 12 is an explanatory view of a conventional table-based tetrahedral division.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st signal conversion device 2 4 Tetrahedral discrimination means 3 Address generation means 4 Basic lattice point data storage means 5 Body-centered lattice point data storage means 6 Weighting coefficient calculation means 7 Interpolation means 10 First signal conversion device 11 Even-odd address generation Means 12 Even basic grid point data storage means 13 Odd basic grid point data storage means 14 Even body-centered grid point data storage means 15 Odd body-centered grid point data storage means 16 Even-odd weight coefficient calculation means

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H04N 1/46 H04N 1/40 D 1/46 Z

Claims (3)

[Claims] 1. A signal conversion method for obtaining an output signal by interpolating data of lattice points of a body-centered cubic lattice composed of respective upper bits of three input signals, which are adjacent to each other.
The two body-centered lattice points of one unit cube and two basic lattice points located at the boundary between the two unit cubes and adjacent to each other are divided into tetrahedrons, and the data in the tetrahedron is divided into the four A signal conversion method characterized by being obtained by interpolating vertex data. 2. A signal conversion device for interpolating data of lattice points of a body-centered cubic lattice composed of respective upper bits of three input signals to obtain an output signal, wherein two adjacent unit cubes are used. It is divided into tetrahedra whose two vertexes are two basic lattice points located at the boundary between one body center point and the two unit cubes, and which one of the tetrahedrons the three input signals exist in is divided. Tetrahedral discriminating means for discriminating, address generating means for generating an address of the discriminated vertex of the tetrahedron, basic lattice point data storing means for storing data of basic lattice points, and data for body-centered lattice points are stored. Body-centered lattice point data storage means, weighting coefficient calculation means for calculating a weighting coefficient of the apex for interpolating data in the determined tetrahedron, basic data storage means, and body-centered data storage means Or Signal converting apparatus characterized by comprising an interpolation means for performing interpolation processing on the basis of the weighting factor from the weighting factor calculating means two vertex data each. 3. The even-numbered basic grid point data storage means for storing the data of the even-numbered basic grid points and the odd-numbered basic grid point data storage for storing the data of the odd-numbered basic grid points. The body-centered lattice point data interpolating means stores even-numbered body-centered lattice point data storage means, and odd-numbered body-centered lattice point data storage means. 3. The signal conversion device according to claim 2, comprising a lattice point data storage means.
However, the coordinates of the basic lattice point and the body-centered lattice point are (l, m, n), (l-0.5, m-0.5, n-0.
5) It is expressed as {l, m, n: integer}, and is an even point when l + m + n is an even number and an odd point when l + m + n is an odd number.