JPH0224073B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a scan line interpolation technique in a video plate making system for producing printing films or printing separations from television signals.

When comparing an image obtained from a television signal with a photograph taken directly with a camera, the former is significantly inferior in image quality to the latter. There are various reasons for this, but the unavoidable cause lies in the television system itself. In other words, in the standard television system, one screen consists of 525 scanning lines (482 effective lines), so if the screen size is about A5 size, the scanning line density is 3.2 lines per 1 mm. Then you can see the scanning line. In order to resolve this,
Conventionally, methods such as wobbling, in which the electron beam is slightly waved by superimposing a minute alternating current on the deflection circuit of a cathode ray tube, and methods in which the focal point of the electron beam is slightly shifted to make the bright spot larger, have been adopted. This also causes a decrease in resolution and degrades image quality. In contrast, the scanning line density in general printing is 6 to 28 lines per mm, so the scanning lines are invisible, and the image quality is much better than that of printed matter made from television image quality. A more effective way to deal with this problem is the interpolation method, which focuses on the correlation between scan lines. are increasing. Conventionally, as an example of incorporating an interpolation section into a plate-making table, a television image plate-making apparatus has been disclosed in Japanese Patent Application Laid-Open No. 56-8144. However, the interpolation method disclosed in this device is a simple average value interpolation method and cannot be considered effective for all image information, and the number of interpolations is only one point between pixels. However, it can be said that the resolution is insufficient. In addition to the average interpolation method, there are also known interpolation methods that use a larger amount of data, such as the Cubic convolution method, bilinear method, and nearest neighbor method. The law is known.
Of these, the Cubic convolution method is the most sophisticated and can perform the best interpolation. It is thought that the best interpolation can always be achieved if the method is used. However, when we actually perform interpolation on a TV screen, we find that depending on the image structure, better results can be obtained by using the bilinear method or nearest neighbor method than by the Cubic convolution method. I understand. For example, in the case of an image composed of vertical and horizontal lines, better interpolation can be achieved by interpolating using the bilinear method. Therefore, an interpolation device that can employ only one type of interpolation method has the disadvantage that it cannot perform good interpolation for various images.

In addition, in the case of interpolation calculations using the Cubic convolution method, it is necessary to perform complex calculations taking into account 16-pixel data, so the processing is usually done using computer software. In this case, the device becomes simpler, but the disadvantage is that the processing takes a long time. Traditionally, video plate-making equipment has been required to perform fairly high-speed processing, so when processing with software as described above, the data for each pixel that has been calculated is stored one after another in a buffer memory, and the data for one screen is stored one after another in a buffer memory. When the calculation is completed, it is necessary to sequentially output the calculation results while synchronizing with the output device. However, the memory for one screen has a large capacity of about 2.5 megabytes or more, and the need for such a memory is extremely disadvantageous.

The purpose of the present invention is to solve the above-mentioned problems and to provide a scanning line interpolation device that can select an appropriate interpolation method from the three methods of Cubic convolution method, bilinear method, and nearest neighbor method depending on the image. This is what we provide.

The present invention provides a video image plate-making apparatus for creating a printing film or a printing separation plate from a television image, which performs interpolation using the Cubic convolution method, bilinear method, or nearest neighbor method to create a scanning line within a scanning line. The present invention is characterized in that it is provided with means for inserting images, and means for selecting one of the Cubic convolution method, bilinear method, and nearest neighbor method depending on the content of the image.

Still another object of the present invention is to provide a scanning line interpolation device for a video image plate-making system that is quick and has good resolution by using a logic circuit constructed of elements suitable for high-speed processing.

A scanning line interpolation device for a video image plate making system according to the present invention that achieves the above object is used in a scanning line interpolation device installed in a video image plate making apparatus that creates a printing film or printing separation plate from a television image. , an interpolation unit having a ROM unit that stores pixel coefficients used in interpolation calculations and an interpolation calculation circuit; The pixel values of 16 pixels around the interpolation point, which are two-dimensionally distributed, are multiplied by a pixel coefficient representing the correlation with the interpolation point, and the sum is used as the interpolation value of the interpolation point. , x and y are distances in the main scanning direction and sub-scanning direction, respectively, and the pixel interval in these directions is 1, then the pixel coefficient is expressed by the following formula α ₁ (x, y)={1-2|x | ² + | x | ³ } {1-2 | y | ^{2 +} | _y | 3 } 0 ≦ | −2 | ^{x | 2 +} | α ₃ (x,y)={4-8|x|+5|x| ² −|x| ³ }{1-2|y| ² +|y| ³ } 1≦|x|<2,0≦ |y|<1 ...(3) α ₄ (x, y)={4-8|x|+5|x| ² −|x| ³ }{4-8|y| +5|y| ² −| y｜ ³ ｝ 1≦｜x｜＜2,0≦｜y｜＜2 ……(4) α ₅ (x, y)=0 2≦｜x｜, 2≦｜y｜ ……(5) In the given Cubic convolution method, assuming that the level of the image signal between the scanning lines adjacent to the interpolation point changes linearly between the scanning lines, the plurality of pixel values are multiplied by the pixel coefficients and the sum is calculated. Bilinear method to calculate the interpolated value as,
The nearest neighbor method calculates an interpolated value by multiplying the plurality of pixel values by a pixel coefficient and calculating the sum of the pixel values so that the pixel values on the scanning line adjacent to the interpolation point are directly used as the interpolated value of the interpolation point. a plurality of ROMs storing the pixel coefficients for each interpolation method;
a ROM for selecting one of the three interpolation methods according to the content of the television image, and a ROM storing pixel coefficients for the selected interpolation method; The interpolation calculation circuit includes a frame memory that stores pixel data, and a frame memory that outputs the pixel data of the plurality of rows and columns from the frame memory for each column. The present invention is characterized by having a plurality of arithmetic circuits for calculating pixel data at interpolation points obtained by reading out pixel coefficients corresponding to the pixel coefficients from the selected ROM.

Hereinafter, the present invention will be explained in detail with reference to the drawings. Here, first, an outline of an image interpolation method will be explained, and then embodiments of the present invention will be explained with reference to the drawings. Interpolation methods conventionally used in image processing include the nearest neighbor method and the bilinear method. The bilinear method treats the image data as changing linearly between adjacent scanning lines. For example, as shown in FIG. 9A, the pixel data of the adjacent first scanning line and second scanning line are and B, the interval between scanning lines is a, and the interval between the first scanning line and the desired interpolation point is x, then the desired interpolated value X is X=B+(A-B)(a-x)/ It is found as a. Therefore, when the interpolation point is located between adjacent scan lines, the interpolation value will be the average value of A and B. The nearest neighbor method assumes that the data between adjacent scanning lines does not change, and uses the data of the previous scanning line as is during interpolation.
=A. Therefore, the nearest neighbor method is effective for images consisting only of binarized black and white, and the bilinear method is effective for images with halftones that change linearly, but many images are Many of them have both large areas and mid-tone areas, and neither of these methods yields satisfactory results. Of course, the correlation between a point to be interpolated and surrounding pixels is greatest for the adjacent pixels, but furthermore, the correlation with pixels on the outer periphery cannot be ignored. On the other hand, since the nearest neighbor method and the bilinear method ignore this correlation with pixels on the outer periphery, they are valid only under the above-mentioned special conditions. Various interpolation methods have been proposed that take into account the correlation with peripheral pixels, but the method adopted in the present invention is called the Cubic convolution method, which takes into account the influence of 16 peripheral pixels. These 16 things to consider
The pixel data is multiplied by a pixel coefficient representing the correlation to find the sum total, and this is used as data at the desired interpolation point. In the embodiment of the present invention, the standard television system, interlaced scanning, is switched to progressive scanning, and three scanning lines are interpolated between each scanning line, resulting in an effective 1924 scanning lines. When exposed to light, the scanning lines are erased so that they partially overlap. At this time, the scanning line density will be approximately 13 lines per 1 mm for A5 size, so
It is almost the same level as normal printed matter, and can be put to practical use. Further, by performing the above interpolation, the number of scanning lines is not only increased, but also the original data can be restored, so the resolution is increased by about 1.2 to 1.3 times. Interpolation calculations are also required for conversion in the scanning direction. When shooting a TV screen, it may be necessary to turn the horizontal screen vertically, and each screen may be arranged so that the same screen is arranged horizontally and vertically on one screen. There may be times when shooting at different times. At this time, from the screen scanned in the horizontal direction, the pixel data necessary to form a scanning line with a density that can be used for vertical printing is obtained by interpolation calculation, and this scanning line data is used. By scanning in the horizontal direction, a horizontal image can be made vertical. Furthermore, when the main scanning of the video image capturing device used as the output device of this system is a digital value, and when the input signal of the prepress scanner is a digital value, all pixel data is obtained by interpolation calculation. There is a need. Each of the above three types of interpolation methods has its own characteristics, and for binarized black and white images, the nearest neighbor method is
Since the bilinear method is effective for halftone images that change linearly, the configuration is such that any method can be selected along with the Cubic convolution method.

Conventionally, there has been no idea of switching between these methods depending on the image quality, but according to the present invention, the most effective interpolation method can be freely selected depending on the image quality. Furthermore, in the present invention, interpolation calculations are performed by a logic circuit composed of arithmetic elements capable of high-speed calculations, making calculations possible in real time and eliminating the need for buffer memory, which significantly simplifies the configuration. can.

Next, embodiments of the present invention will be described in detail with reference to the drawings. In addition, in the video plate making system, the standard television method is the three primary colors R,
Since the signal is decomposed into G and B and interpolation calculations are performed for each of R, G, and B, three systems of interpolation calculation circuits, which will be described below, are prepared.

FIG. 1 is an explanatory diagram showing the relationship between pixels of an original image and interpolated values. The number of pixels in the scanning line direction is 756 by sampling with 4 _SC pulses. Here, _SC is the color subcarrier at 3579545Hz. According to the sampling theorem, the original image can be restored by sampling at a frequency that is at least twice the maximum frequency included in the image. In this example, the highest image frequency of the NTSC video signal is 6 MHz or less in general imaging equipment, whereas the _4SC is 14 MHz or more, so the above conditions are fully satisfied and the restorability is good. Also, in the case of high-resolution signals such as RGB format, the sampling frequency of 4 _SC may be insufficient, so for example
If set to 6 _SC (21.48MHz), the maximum image frequency is 10M
Hz or higher, allowing for more detailed digitization and interpolation. Furthermore, when sampling is performed using pulses that are even multiples of _SC in this manner, each pixel is arranged linearly in both the x and y directions as shown in FIG.

FIG. 2 is a block diagram showing a circuit for A/D conversion of scanning lines and scanning method conversion. In the A/D converter 1 in FIG. 2, the pixels of the scanning line are sampled and digitized as described above, and then stored in the frame memory 2 by the write control circuit 3, and then by the read control circuit 4. The scanning lines of odd and even fields are read out alternately. In this way, the interlaced scanning method is switched to the progressive scanning method, and it is possible to prevent bearings in which the spacing of the scanning lines is not uniform in some parts, resulting in a striped pattern.

In the present invention, the data at the point to be interpolated is the sum of the products of the data of 16 adjacent pixels and the pixel coefficients of each pixel, as described above. This pixel coefficient represents the degree of correlation between the point to be interpolated and each pixel.
If the axis and y-axis are taken in the main scanning direction and the sub-scanning direction,
When the pixel spacing in the x-axis and y-axis directions is 1, for example, in the Cubic evolution method, it can be expressed using the following approximate expression.

α ₁ (x,y)={1-2|x| ² +|x| ³ }{1-2|y| ² +|y| ³ } 0≦|x|<1,0≦y<1... …(1) α ₂ (x,y)={1-2|x| ² +|x| ³ }{4 −8|y|+5|y| ² −|y| ³ } 0≦|x|<1,1≦|y|<2...(2) α ₃ (x, y)={4-8|x|+5|x| ² -|x| ³ }{1-2|y| ² +| y｜ ³ ｝ 1≦｜x｜＜2,0≦｜y｜＜1 …(3) α ₄ (x, y) = {4-8｜x｜+5｜x｜ ² −｜x｜ ³ } {4-8|y| +5|y| ² −|y| ³ } 1≦|x|<2,1≦|y|<2 ...(4) α ₅ (x, y)=0 2≦| x|, 2≦|y| ...(5) Each pixel coefficient α ₁₁ to α ₁₄ is calculated using the above formula, and even if the interpolation point is inside the shaded area, it may vary depending on the location. The values are different. The above explanation is an example based on the Cubic convolution method, but when applying the bilinear method or the nearest neighbor method, by appropriately selecting α ₁₁ to α ₄₄ , the Cubic convolution method can be applied. can be processed in the same way by the circuit in . If each pixel data and pixel coefficient are expressed by Pij and αij, the data at the interpolation point can be expressed by the following equation.

P= ₄ 〓 ⁱ⁼¹ ₄ 〓 ⁱ⁼¹ αij・Pij ...(6) Generally, the sum of 16 pixel data is calculated using the above equation (6), but if the interpolation point is the 1 figure x ₁₀ ,
When it is on a pixel column such as x ₂₀ and x ₃₀ , the pixel coefficients of pixels on other columns are all 0, so the amount of calculation is reduced to one-fourth. In this example, in order to be compatible with an output device that receives all pixels as digital values as described above, a circuit that can perform interpolation calculations for the 16 pixels described above is implemented. ROM when interpolating on a pixel column and when interpolating on a pixel column
This is done by exchanging the In addition, in this embodiment, the distance between adjacent scanning lines is 4.
It was configured to divide the image into equal parts and obtain four scanning lines by interpolation. One of the four lines is on the original scanning line, but since it was obtained by interpolation calculation, the calculation process is the same as for the other scanning lines. In this example, four scanning lines are interpolated, but if four scanning lines are not necessary, two or three scanning lines may be used, and if there is a shortage, five or six scanning lines may be used. In either case, calculate 16 pixel coefficients for each interpolation point using equations (1) to (5).
Write it in ROM and use it repeatedly for interpolation calculations. Pixel data read from the frame memory 2 is sent to an interpolation calculation circuit, stored in a line RAM, and combined with a ROM in which pixel coefficients have been written to obtain a required interpolation value. First, 4 at the top of the screen.
Write the scanning line of the book into RAM, find x ₀₀ in Figure 1 for the leftmost 16 pixels, and then find each pixel on the original scanning line in the same way. Next, the same operation is repeated to find each pixel in the second row, and then each pixel in the third and fourth rows to form four new scanning lines. Furthermore, the first row is erased, the fifth row is written into the RAM, and four new scanning lines including the third row are formed in the same manner. In the same manner, the interpolation is completed until the bottom of the screen is reached.

FIG. 3 shows the RAM in one embodiment of the present invention.
FIG. 3 is an explanatory diagram showing a method of combining ROMs. RAM
There are two ways to combine ROM and ROM: a method that uses one type of ROM, and a method that does not rewrite RAM.
To find the interpolation point within the interpolation _range As shown in Figure 3B, ROM-1~
Store in ROM-4, RAM-1 and ROM-1,
RAM-2 and ROM-2, RAM-3 and ROM-3,
This is possible by multiplying the corresponding pixel data and coefficients of RAM-4 and ROM-4 and finding the sum. Next, to obtain the _interpolated data in All you have to do is multiply them and find the sum. In this case RAM and ROM
There are two ways to combine, one of which is the third
The ROM is shown in Figure C, and the ROM stores pixel coefficients A' to D', respectively, as shown in Figure 3B.
Using only one set of ROM-1 to ROM-4, RAM-1 to
The RAM-4 is always written in ascending order of scanning line numbers, and the other one is to change the order of pixel coefficients A' to D' one by one as shown in Figure 3C. ~What is stored in ROM-4 4
The pixel data of the RAM that was set up and written is left as is, and the RAM that stored the first line is
-1 to write a new fifth line. The same applies to the interpolation points within X ₃ , X ₄ and X ₅ below, but _the combination is the same as the interpolation within
The rows written in RAM-1 to RAM-4 are arranged in numerical order, and each ROM has the same arrangement as the ROM of _X1 . In other words, the same state is repeated every four rows. According to the combination shown in Figure 3C, only one set of ROM is required, but the contents of RAM must be rewritten each time the interpolation point is moved between adjacent scanning lines, and four 8-bit selectors are required. . When rewriting the contents of RAM, the rewriting time becomes longer and processing cannot be completed in time. The combination shown in the figure requires four sets of ROM, but the required
If you use a ROM element that matches the total capacity of the ROM, you only need to specify the address, so there is no need to use a separate ROM element for that purpose, which simplifies the configuration and eliminates the need to rewrite the contents of RAM, so processing Time is reduced.

Next, the necessity of high-speed processing and the countermeasures taken in the present invention will be explained. As mentioned above, even if measures are taken to improve the image quality, printed matter made from television signals is not as good as those made from photographs taken directly with a camera, so it is intended for use in situations where many small-sized items are handled. Therefore, high-speed processing is required. Further, in order to match the operating speed of a color scanner which is an output device of a video plate making device, the interpolation calculation speed needs to be considerably high per pixel. Furthermore, video photography equipment, which is the same output device, requires even higher processing speeds due to the stability of the FSS tube's deflection circuit. Among the above-mentioned requirements, the requirement for stability of the deflection circuit is the most severe. To perform interpolation calculation for one pixel, it is necessary to calculate αij and Pij 16 times and find the total sum, and the number of interpolation points for one screen is 1448772. Since it is impossible to expect such a large amount of calculation to be processed in a short time using a computer software program, the present invention uses a logic circuit constructed of elements suitable for high-speed processing. Furthermore, as a result, it became possible to send pixel data directly to the output device, which eliminated the need for memory for one screen, making it possible to significantly simplify the configuration. Reading the memory takes the most time when calculating interpolated data, but
Access time is normal MOS for one read.
Since 150 to 200 nsec. is required for RAM, it becomes 2.4 to 3.2 μS for 16 calls, which does not satisfy the required conditions. Therefore, in the present invention, this time is reduced by providing four identical calculation circuits and performing parallel calculations.

FIG. 4 is a diagram showing the configuration of the interpolation calculation circuit. In the figure, for the reasons mentioned above, input buffer 5, line-in RAM 7, multiplier and adder 9
4 circuits are provided for each. Pixel data read out from frame memory 2 in a sequential manner is written to line RAMs 7a-7d via input buffers 5a-5d. This writing control is performed by AW, BW, CW, and DW write control signals. Read control is performed by applying an address signal to each RAM via the address buffer 6, and the line RAM 7a
~7d data is sent to multipliers and adders 9a~9d. On the other hand, data in a predetermined ROM passes through a pixel coefficient buffer 8 and is then sent to multipliers and adders 9a to 9d.
calculation is performed. The combination of the scanning line number and the ROM line number is shown in Figure 3C.
It is carried out by a combination of The respective outputs calculated by the multipliers and adders 9a to 9d are further added by an adder 10, and outputted via a bus buffer 11.

FIG. 5A is an explanatory diagram showing the progress of interpolation calculation in the upper left corner of the screen. In the first step, the multipliers and adders 9a, 9b, 9c, and 9d receive P ₁₁ , P ₂₁ , P ₃₁ , and P ₄₁ from the RAMs 7a to 7d.
Further, α ₁₁ , α ₂₁ , α ₃₁ , and α ₄₁ are sent from the ROM and multiplied respectively. In the second step, RAMs 7a to 7d are similarly
P ₁₂ , P ₂₂ , P ₃₂ , P ₄₂ from ROM are α ₁₂ , α ₂₂ , α ₃₂ ,
α ₄₂ is fed into a multiplier and an adder to perform multiplication and addition with previously calculated data. Multiplication and addition are performed in the same manner in the third and fourth steps, and in the fourth step, P _A , P _B , P _C , and P _D are obtained. Next, when these data are sent to the adder 10 and the sum is determined, that value becomes the data at the interpolation point.

FIGS. 6 and 7 are explanatory diagrams showing the configuration of the ROM and the reading method for each interpolation method and each interpolation point. The value of ROM varies depending on various interpolation methods and the position inside the diagonal line shown in Figure 1, and the value of ROM varies depending on the interpolation range X ₁ , X ₂ , X ₃ , X ₄ shown in Figure 3 A. The combinations are different. Once the interpolation position is determined, the pixel coefficients can be determined using the aforementioned equations (1) to (5), and a ROM can be manufactured by writing this data as shown in FIG. The interpolation calculation is configured such that once the interpolation method is selected, the necessary ROM is read out according to a predetermined sequence and the calculation proceeds automatically. There are three types of interpolation methods: the aforementioned Cubic convolution method, bilinear method, and nearest neighbor method. The interpolation method selection switch 13 shown in the figure switches the interpolation method, and then the address selection circuit 14
A predetermined position in the ROMs 16a to 16d is selected by the ROMs 16a to 16d. ROM16a~16d
The configuration contents of each are shown in FIG. 7, and in this case, the type of interpolation method mentioned above, the _position of the interpolation range
X ₂ , X ₃ , X ₄ , and interpolation position in each interpolation range
It is divided into x ₀₀ , x ₁₀ , x ₂₀ , x ₃₀ , and each is further divided into four areas, A', B', C', and
The pixel coefficients of any row of D′ are stored.
In the present invention, the ROM is used to change the interpolation position.
I am trying to replace it. For example, to move the interpolation points x ₀₀ , x ₁₀ , x ₂₀ , x ₃₀ on the original pixel column to the center position of the adjacent pixel column x ₀₂ , x ₁₂ , x ₂₂ , x ₃₂ , use (6) All you have to do is replace the ROM with the pixel coefficients calculated using the formula. In order to increase the number of interpolation columns, it is necessary to add a ROM having a configuration similar to that shown in FIG. 6 and recording the pixel coefficients of each column. In addition, to increase or decrease the number of interpolation rows, that is, the number of scanning lines caused by interpolation, please refer to Figure 6.
It is necessary to change the ROM configuration. To give an example of the data written in the ROM in this embodiment, in the first row of the interpolation range of X ₁ , α ₁₁ is set to 16a,
α ₁₂ , α ₁₃ , α ₁₄ ; α ₂₁ , α ₂₂ , α ₂₃ , α ₂₄ in 16b;
1
α ₃₁ , α ₃₂ , α ₃₃ , α ₃₄ in 6c; α ₄₁ , α ₄₂ , in 16d
α ₄₃ and α ₄₄ are written, and the first of the interpolation range of X ₂
In the row 16a, α ₄₁ , α ₄₂ , α ₄₃ , α ₄₄ ; in 16d, α ₁₁ , α ₁₂ , α ₁₃ , α ₁₄ ; in 16c, α ₂₁ , α ₂₂ , α ₂₃ ,
α ₂₄ ; α ₃₁ , α ₃₂ , α ₃₃ , and α ₃₄ are written in 16d.

FIG. 8 is an explanatory diagram showing the interpolation order of each interpolation point constituting one screen. The interpolation calculation at each interpolation point is performed by multiplying the pixel coefficient of each pixel by the pixel data and calculating the sum, as explained using FIG. As shown in Figure 8, the interpolation is performed by starting from the left to the right and calculating the pixel data at each interpolation point at the top of the interpolation position x ₀ in the range X ₁ between the second and third rows at the top of the screen. Find and complete one scanning line x ₀ . The number of pixels in the original scanning line is 756, but the number of interpolation points is 753, so three points (0.4%) are lost. Next, switch the ROM, find x ₁ in the same way, and then find x ₂ and x ₃ in the same way. After that, the interpolation points of x ₀ , x ₁ , x ₂ , and x ₃ are determined for the position of X _2. At this time, according to Figure 3C, 5
The pixel data of the column is written and the combination of ROMs also changes. In the same manner, the interpolation calculation for the entire screen ends when X ₄₈₁ is reached. The initial number of scan lines is 484, and the interpolation position is 481, so the lines at the top and bottom (0.62%)
Lost.

As explained in detail above, in the present invention,
Since we have made it possible to select the most suitable interpolation method depending on the content of the image, the image quality of the projected image can be significantly improved, and the image quality of printed matter printed using the print separation plates we will create will be improved. I was able to improve it significantly. Interlaced scanning can be converted to progressive scanning to prevent pairing, and interpolation can increase the number of scan lines to make them invisible and improve resolution. Furthermore, since an extremely high-speed interpolation calculation circuit was constructed using a logic circuit constructed of elements suitable for high-speed processing, it was possible to construct a stable video plate-making system that is highly operable and practical. Furthermore, the present invention makes it possible to eliminate the need for large-capacity memories and many selectors, and has a great effect in simplifying the circuit configuration.

Further, the present invention is not limited to the above-described embodiments, and many modifications and changes are possible. For example, in the present invention, three types of interpolation methods can be selected, but if it is not necessary, two or one type can be used.Although the number of scanning lines is quadrupled by interpolation, other It is also easy to make multiples. moreover,
Although an object of the present invention is to provide an interpolation device suitable for a digital plate-making device, similar effects can be expected by utilizing the present invention to improve image quality in other applications.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the relationship between a set of pixels and interpolation points in the Cubic convolution method.
Figure 2 is a circuit diagram of scanning line A/D conversion and scanning method conversion, Figure 3A is an explanatory diagram showing the relationship between each pixel and the interpolation position, and Figure 3B is a set of pixel coefficients stored in ROM. , FIG. 3C is a table comparing the present invention and other methods of scanning lines written to RAM and pixel coefficients written to ROM at each interpolation position, FIG. 4 is a block diagram showing an interpolation calculation circuit, and FIG. Figure 5 is an explanatory diagram of the interpolation calculation method for one pixel, Figure 6 is the circuit diagram around the ROM, Figure 7 is the ROM address configuration diagram, and Figure 8 is the interpolation order and interpolation range for one screen. Explanatory drawings, FIGS. 9A and 9B are diagrams for explaining the interpolation method. 2...Frame memory, 5...Input buffer, 6...Address buffer, 7...Line RAM,
8... Pixel coefficient buffer, 9... Multiplier and adder,
10... Adder, 11... Bus buffer, 13... Interpolation method switch, 14, 15... Address selector, 16...
Line ROM.

Claims (1)

[Scope of Claims] 1. In a scanning line interpolation device provided in a video image plate-making device that creates a printing film or printing separation plate from a television image, a ROM section that stores pixel coefficients used in interpolation calculations; an interpolation unit having an interpolation calculation circuit, and the ROM unit is configured to calculate 16 pixels around the interpolation point that are centered around the interpolation point and distributed two-dimensionally over multiple rows and columns in the vicinity of the interpolation point. The pixel value is multiplied by a pixel coefficient representing the correlation with the interpolation point, and the sum is used as the interpolation value of the interpolation point, where x and y are distances in the main scanning direction and sub-scanning direction, respectively. When the pixel interval in these directions is 1, the pixel coefficient is expressed by the following formula α ₁ (x, y)={1-2|x| ² +|x| ³ }{1-2|y| ² + |y| ³ } 0≦|x|<1, 0≦y<1 ...(1) α ₂ (x, y) = ^{{ 1-2} | 8 | y | + ⁵ | _y | ² − | y | +5 | x | ² − | x | ³ } {1-2 | y | ^{2 +} | y | 3 } _{1 ≦} | y)={4-8|x|+5|x| ² −|x| ³ }{4-8|y| +5|y| ² −|y| ³ } 1≦|x|<2, 1≦| y|<2 ...(4) α ₅ (x, y)=0 2≦|x|, 2≦|y| ...(5) Cubic convolution method given by, adjacent to the interpolation point The bilinear method calculates an interpolated value as the sum of the plurality of pixel values by multiplying them by a pixel coefficient, assuming that the level of the image signal between the scanning lines changes linearly between the scanning lines, Each interpolation method of the nearest neighbor method calculates an interpolated value as the sum of the multiplied pixel coefficients by multiplying the plurality of pixel values so that the pixel value on the scanning line is directly used as the interpolated value at the interpolation point. It has a plurality of ROMs storing the pixel coefficients for each ROM and a switch for switching these ROMs, and selects one of the three interpolation methods according to the content of the television image, and selects the selected interpolation method. The interpolation calculation circuit includes a frame memory for storing pixel data, and a ROM for storing pixel data from the frame memory. It is characterized by having a plurality of arithmetic circuits that read out pixel data in a plurality of rows and columns for each column, read out corresponding pixel coefficients from the selected ROM, and calculate pixel data at an interpolation point to be obtained. A scanning line interpolation device in a video image prepress system. 2. The interpolation calculation circuit includes means for reading the pixel data of the plurality of columns and plurality of rows surrounding the required interpolation point from the frame memory for each column, and amplifying each of the read pixel data of each column. Multiple input buffers, multiple RAMs that temporarily store the output of these input buffers, and
A plurality of multipliers/adders that multiply and add each pixel data read from the RAM and each corresponding pixel coefficient read from the ROM for each pixel, and addition of output signals of the plurality of multipliers/adders. Claim 1 comprising an adder that performs
The scanning line interpolation device described in Section 1. 3. When sequentially performing interpolation calculations on the pixel ranges of multiple adjacent columns and rows while shifting the pixel ranges containing multiple adjacent columns and rows by one scanning line in the vertical direction, of the interpolation calculation circuit that stores pixel data of scanning lines;
The data in RAM is left as is, and the pixel data of the newly added scanning line is written to the RAM location where the pixel data of the scanning line that is no longer included in the new pixel range was stored, and the pixel coefficient data of each row is are stored in different order line by line.
A ROM was provided, and as the pixel range was shifted, pixel coefficient data was stored in the same order as the arrangement order of each row of pixel data stored in the RAM.
2. The scanning line interpolation device according to claim 1, wherein the interpolation calculation is performed by selecting a ROM.