JPS61170186A - Dot picture forming device - Google Patents

Abstract

PURPOSE:To form a dot picture having a screen angle in high speed by storing plural sets of information relating to a dot area rate and shape of a dot pattern, averaging contrast information of a dot picture at every picture element unit and using the averaged value as an address so as to read the information of the dot pattern at every specific period. CONSTITUTION:When (U+V) lines of picture data are written in an input picture memory 15, the address of the memory data of an inputted dot pattern is commanded by a CPU10 and inputted sequentially to an averaging circuit 17. The result of the averaging is inputted to a dot pattern ROM18 in which 18 dot patterns are stored and a dot pattern corresponding to the result of calculation is selected from the output of a ROM18 automatically. Then an address control circuit 20 commands the data output of the corresponding address from the dot pattern ROM18 according to the command of the CPU10 and outputs a write address to an output picture memory 19 at the same time.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a color scanner for color separation printing, and a halftone image forming device that forms a halftone image at a desired screen angle by scanning an original image. Regarding.

[Prior Art] In general, a halftone image forming apparatus forms a halftone image by setting a different angle for each colorant on a mesh screen to eliminate a moiré image caused by the overlapping of each colorant. When recording a halftone image with halftone dots, a threshold corresponding to each pixel forming the halftone dot is set as the shape information of the halftone dot, and this threshold is compared with the image signal obtained by scanning the original image. An output scanning line control signal is formed depending on the magnitude.

As another example, as shown in Equity No. 1152-49361, select the rational tangent of the angle closest to the desired screen angle, and use the periodicity on the scanning line of both halftone images at this time. There is something that says.

That is, as shown in the example of halftone dots formed by rational tangents in FIG. 6, if the screen pitch in the main scanning direction x 1 sub-scanning direction Y is .U, then the rational tangent is 1: a nα
-U, /, V roar, screen angle is α-jan
"U/V".The screen angle is selected in this way, and from the selected rotating mesh screen, there is a cutting boundary line in the main scanning direction and the sub-scanning direction, and with respect to each of the main scanning direction and the sub-scanning direction. A cut-out portion that corresponds to the basic period of the structure of the rotating mesh screen is taken out, a mesh screen signal corresponding to the structural content of this cut-out portion is generated, and this mesh screen signal is applied at a sufficient frequency to the pattern of the screen. It is designed to be repeated periodically.

[Problems to be Solved by the Invention] However, in these halftone image forming devices, the necessary The amount of input data increases. For this reason, the memory capacity for storing this input data becomes large, and there is a problem that high speed cannot be expected and the installation structure becomes complicated.

The present invention was made in view of the above problems, and allows the screen angle to be set for any rational tangent value.
The purpose of this invention is to form a halftone image having the screen angle at high speed.

Means for Solving Problem F The present invention stores a plurality of pieces of information regarding the halftone dot area ratio, shape, etc. of a halftone dot pattern based on a halftone dot image of a desired Sufflone horn turtle, and stores information on the halftone dot area ratio, shape, etc. It is characterized in that information is read out at specific intervals using the average value of the m degree information of the halftone dot image as an address.

[Effect 1] Therefore, the present invention is based on the screen angle α-jan 'tJ/V which can be obtained from FIG. GCD (LJ, V) (Tatashi GCD (U =
It attempts to use the period 1 on the scanning line derived from the periodic pattern length 1-1 Δ/P, etc. , for example, when the screen angle is 0° for U-0, V=4, there are four different halftone dot patterns with periodic pattern lengths 1--4, and u=i, v-4. When the screen angle of 4 is 14 degrees, a halftone dot pattern with one type of shape of 1=17 is created, and when the screen angle of U=3 and V=3 is 45
Degree Nosuke can produce halftone dot patterns of different shapes in three scales 1 to 6.

In other words, as shown in FIG.
1111, and in the case of an orthogonal screen, it also circulates periodically in the sub-scanning direction. From this, it can be seen that the periodic pattern of halftone dots is composed of LXP and is repeated at a period P in the sub-scanning direction. P in this sub-scanning direction ('lI When the scan moves, D from the starting halftone dot position of the previous scanning line.
The next halftone dot is formed at the location where the halftone dot 111 is removed. This D
By using a periodic pattern composed of LXP, it is possible to form a halftone dot image at a desired screen angle. This D can be determined by D-1/V (P-U+t-A) (where t is the smallest positive integer for which D is an integer). , Further, calculate the value of the shift parameter S using 1--D, and shift the periodic pattern to the left by the value S by 1 to 1 every time P is moved in the sub-scanning direction.By repeating the above operation, a screen can be formed. Therefore, the circulation of the periodic pattern becomes easy.

Therefore, the present invention stores a halftone dot pattern based on a halftone dot image in advance in a memory, averages the periodic pattern of the above halftone dot image for each pixel as an address value, and calls the halftone dot pattern. This is directly output as halftone image data.

[Example] An example of the present invention will be described in detail based on the drawings of FIGS. 1 to 5.

FIG. 1 is a functional block diagram of the device of the present invention, where 10 is a central processing unit (CPLJ) r, this cPUlo is a RAM 13 for reading and writing, and an R for storing programs to be described later.
The OM 14 includes an address circuit 16 that controls the write and read addresses of the input image memory 15 that stores the input image in (U+V) lines, and an adder circuit 17a that averages the output of the previously installed image memory 15. Division circuit 17b
a halftone dot pattern ROM that outputs a corresponding halftone dot pattern from the output of the averaging circuit 17;
18 and the output data from the halftone dot pattern are stored in the output image (LJ +V) line. 1, connected via an address bus 12. Further, an input image device 21 is connected to the input image memory 15 and outputs the input image to the input image storage 15. An output image device 22 such as a printer is connected to one of the output image memories and records the output image from the output image memory 19.

FIGS. 2(a) and 2(b) show the manual data memory of the input image memory 15 and the output data memory of the output image memory 19, both of which are composed of (C10V) lines. (The 1lt 1 degree information read by both scans is read into the input data memory as data for 8 pits 1 to (0 to 255), and this data is
) is output to the output data memory as the data.

In order to perform the opening method, the input data configured as shown in Figure 3 (a) is averaged within the halftone dot pattern as shown in (b), and the value is referenced as an address and stored in memory in advance. The stored halftone dot pattern of 1 pixel 1 to (0,1>) is output to the output data memory. It is stored in the pattern ROM 18.

Therefore, for example, the operation of the device shown in FIG.
This will be explained based on flowcharts 1 to 1 in the figure.

First, when the star 1 switch (not shown) is turned on, the three parameters assigned in the RAM 13 in step 100 are set to 0ffSet=Q, count.
=p, x=O, and the first periodic pattern is set to a writable state. Then, the CPU 10 sends a write address to the address control circuit 16, and image data from the input image device 21 is written into the input image memory 15 in accordance with the address. This input ii! ii Image data is stored in the image memory 15 (LJ -1-
V) When a line is written, it means that a complete halftone pattern has been input, so the process proceeds to step 101, whereupon the CPU 10 instructs the memory data address of the halftone pattern that has been input, and sequentially inputs it to the averaging circuit 17. let ′? Also, this halftone dot pattern corresponds to the memory data in the shaded area in FIG.
By adding the seven pieces of data and dividing the added data by the number of f-taters, 17, in the division circuit 17b, it is averaged. This division is performed by repeating subtraction, so the remainder is 0 to 8.
~ is the number of times the subtraction is repeated as the result of the division, and when it is 9 to 16, the result of the division is the number of times the subtraction is repeated by 1-1. The result of this division is the result of averaging, and the result of this averaging is input to the halftone pattern ROM 18 in which the 18 halftone patterns shown in FIG. 4 are stored. As a result, the halftone pattern ROM is automatically stored in step 102.
A halftone dot pattern corresponding to the target calculation result is selected as the output of 18. Next, the address control circuit 20 controls CPjJlo
According to the instruction, data output of the corresponding address is instructed from the halftone dot pattern ROM 18, and at the same time, a write address is output to the output image memory 19. Therefore, in step 103, the output data from the halftone pattern ROM 18 is written into one output image memory by the write command from the address control circuit 20. This completes the processing for the first halftone pattern. Next, for a complete halftone dot pattern as shown in FIG. 7, the main scanning direction hair address is +1-
Since it is also formed in an area that has moved a great deal, step 104
Then, CPU10 sets the parameter × in RAM13 to ×4−“
It is determined in step 105 whether this value has exceeded the end of the column in the image memory area, and if it has not, the process returns to step 101 and the above process is repeated until the column ends.

When CPtJlo determines that the value of parameter × has exceeded the end of the column in the output image memory area by the above processing,
Proceeding to step 106, the cpuio sends a command to the address control circuit 20 to output the halftone dot pattern data input to the output image memory to the output image device 22. Then, in step 107, it is determined whether or not the halftone dot pattern data output to the output image device 22 has been completely completed by the processing described in L. If all has been completed, EN is selected.
The process advances to D and the process is completed. If output J dot pattern data still remains, the process proceeds to step 108, and the contents of the input/output data memory are changed line by line to 7 levels, and in step 109, the 1 line shifted from line P to Shift 1 is subtracted. I will do it. Then, in step 110, data is outputted to the output image device 22 until the numbers 1 to 0 become 0.

Next, when the numbers 1 to 1 become O, the process goes to step 111, the count is set to P again, and the next data is read into the human data memory in step 112 and the above-mentioned process is performed. As can be seen from the figure, the halftone dot pattern to be newly processed is shifted by S in the main scanning direction. Therefore, CPU10 is RAM1
Parameters within 3) Russ-r Tsubu 113roffse
t knee+offset-3 and further step 114
Then, set the parameter In step 117, read the data into the input data memory with the value 0ffSe1-.Step 10
Return to step 1 and perform the processes described in (g) in sequence.

Further, if the start address is positive in step 115, the process directly proceeds to step 117, and the process from step 101 onward is performed sequentially using the value of X as the offset value.

[Effects of the Invention] Accordingly, the present invention stores data information of a halftone dot pattern based on a halftone dot image at a desired screen angle, and stores data information of the halftone dot pattern based on an average value of density information of the halftone dot image at an address address. Since the information is directly read out, the memory capacity can be reduced and access can be performed efficiently, and furthermore, a halftone image having a desired screen angle can be formed at high speed.

[Brief explanation of the drawing]

FIG. 1 is a functional block diagram showing an embodiment of the present invention, FIG. 2 is a data memory, (a) is an input data memory, (b) is an output data memory, and FIG. 3 (a) is a diagram showing an input data memory. (b) A diagram showing the averaged value of the input data of the data,
FIG. 4 is a diagram showing the m-degree distribution of the halftone dot pattern, FIG. 5 is a diagram showing the flow chart of the present invention from 1 to FIG. 6 is a diagram showing an example of halftone dots formed by rational tangents, and FIG. The figure shows the Zhouming bamboo of the halftone dots in FIG. 6. 10...Central processing unit @ (CPU)', 11...Data bus, 12...Address bus, 13...RAM. 14... ROM, 15... Input image memory, 16.
20...Address control circuit, 17...Averaging circuit,
18... Halftone pattern ROM, 19... Output image memory, 21... Input image device, 22... Output image device. FIG. 5 5TART offset = , ). . unt = p 100 t・x=x+L104

Claims (1)

[Claims] In a halftone image forming apparatus that converts an image signal obtained by scanning an original image into a halftone image with a predetermined screen angle based on rational tangent and records it for each pixel, the halftone dot area ratio and the halftone dot pattern of a halftone dot pattern based on the halftone image are A network comprising means for storing a plurality of pieces of information regarding a shape, and averaging the density information of the halftone dot image for each pixel, and reading out halftone pattern information at specific intervals using the averaged value as an address. Point double image forming device.