JPS5941969A - Gradational image recording and processing system - Google Patents

Abstract

PURPOSE:To realize gradational image recording having a high quality by a small quantity of memory, by storing the number of dots being in an independent relation corresponding to light and shade, when light and shade are expressed by plural dots of different colors. CONSTITUTION:One dot is further divided into a dot matrix of 4X4. Ternary dots of black, gray and white are distributed to each picture element of this matrix of 4X4. The ternary assignment in the matrix element is allowed 9 to correspond to being easy to become black, grey and white. In case when black, grey and white consist of (x) pieces, (y) pieces and (z) pieces, respectively, (x)+ (y)+(z) are 16. As to which part of the 4X4 matrix black of (x) pieces is assigned, determination is performed automatically in accordance with (x) pieces. Grey of (y) pieces is determined in the same way. Accordingly, the processing can be executed by only storing the number of pieces of black and grey in the image memory.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Description of the field to which the invention pertains The present invention relates to a gradation image recording processing method, in particular a method in which a plurality of dots having three values of white, gray, and black are formed in one pixel of an image having shading. A recording processing method that expresses gradation by changing the composition of the number of white, gray, and black dots in the plurality of dots, reduces the amount of memory in the gradation recording device, and produces high-quality gradation images. The present invention relates to a recording processing method for realizing recording.

(2) Description of conventional technology Figure 1 shows an example of the configuration of a conventional system of this kind, where ■ is a conventional gradation recording device, 2 is a gradation signal, and 3 is a dot pattern storage for gradation recording. Memory, 4 is buffer memory, 5
is the recording section. In the conventional method of this type, a gradation signal 2 is manually inputted to the recording device 1, a ternary dot pattern of white, gray, and black corresponding to the signal 2 is read out from the memory 3, and then the 3-value dot pattern of white, gray, and black is read out from the memory 3, and then the 3-value dot pattern of white, gray, and black corresponding to the signal 2 is read out from the memory 3.
The information is temporarily stored in the memory 4, and the information is sent to the recording section 5 as needed to record the gradation image. FIG. 1 shows an example in which six gradations are expressed by a 4 x 4 dot pattern, but since it is necessary to store as many ternary dot patterns as the required number of gradations in the memory 3, When trying to express multiple levels or different types of gradation numbers, there is a drawback that the memory size becomes large. In other words, in the case of mXn matrix elements, the number of bits Bc required per gradation is Bc = 2XmX
n bits, 7 bits, k types of gradation number N1 (i = 1.2.
...k) memory capacity is required.

Furthermore, there are generally multiple ways of arranging the ternary dots in the matrix, and although the recording density is constant depending on the dot arrangement, the image quality changes. In other words, depending on the dot arrangement, low frequencies in the spatial frequency such as stripes are noticeable,
Image quality is impaired. Therefore, conventionally, as shown in FIG. 2, several types of patterns with different dot arrangements were prepared for each gradation level, and these were extracted cyclically or randomly and recorded. Alternatively, instead of preparing multiple types as shown in Figure 2, the dot pattern with the smallest low frequency component is selected in advance from among all the dot arrangements in the ternary dot number configuration corresponding to each gradation level, and this is I was using it.

However, in these conventional methods, the former has the disadvantage that the required memory capacity is further increased, and a common disadvantage with the latter is that patterns are selected without considering the influence between gradations and I-pels. As a result, image quality deterioration factors such as false contours and twills are noticeable near boundaries between different gradation levels in the recording section. In addition, Figures 1 and 2
In the figure, black meshes represent black dots, hatched meshes represent gray dots, and white meshes represent white dots.

(3) Purpose of the Invention In order to eliminate these drawbacks, the present invention stores only the number of independent binary dots among the three values of white, gray, and black for each gradation level, and The ternary dots are arranged according to the order of dot arrangement with respect to the placed dot Φ matrix, and the drawings will be explained in detail below.

(4) Explanation of the structure and operation of the invention FIG. 3 is an example for explaining the invention in detail.
A number is assigned to each element of the Tontoro pattern e-matrix of No. 4. These numbers indicate the order in which the three-valued dots of black, gray, and white are assigned to each matrix element, and represent, so to speak, the ease with which each matrix element becomes black, gray, or white. Specifically, when the number of dots in a ternary dot pattern corresponding to a certain gradation level is X black, y gray, and 2 white (x+y+z=16), the number of dots from 1 to X in Figure 3 is is black, (x+1) to (x+y) is gray, (x+y
+1) to 16 are assigned white.

However, if any of X, y, and z is 00, that value cannot be assigned to the dot If. Therefore, in the case of a dot pattern of 6 black, 4 gray, and 6 white dots, such as gradation level 7 in FIG. 2, the numbers 1 to G in FIG.
Gray is assigned to 1o and white is assigned to 11 to 16, and as a result, according to the method of the present invention, the pattern shown in FIG. 4 is generated corresponding to gradation level 7 of FIG. 2. Although the examples shown in FIGS. 3 and 4 show the case where the blocks are laid out in order from black, it is of course also possible to lay out the blocks in order from the millstone.

The examples in FIGS. 3 and 4 show a matrix size of 4×4, but in general mXn (m.

In the case of a matrix size (n is an integer), dot placement orders of 1 to m.times.n may be similarly assigned to the matrix elements. Furthermore, when the matrix size is constant, only the number x, y of one binary dot among the three values can be calculated in advance. are independent, and by using the fact that it can be found by the other 1(d (m
All you have to do is remember that. Therefore, O≦
Since x, y5m×n, the amount of memory required per gradation is Bnta Bn = 2 X c logz (mXn
) ) is the bit where [ ] is the Hagauss symbol.

For example, when m x n = 4 x 4, Bn = 8 bits, and in the conventional method, Bc = 32 bits, so the memory capacity can be reduced to 1/4.

Furthermore, in the present invention, dot placement orders are assigned to matrix elements in the manner shown in FIG. 5, so that high-quality recording can always be achieved. Figure 5 is number 1
As an example, the case where the allocation is completed by 13 and the next position is to be determined is shown. The order assigned to matrix elements is 1 to 1 based on the ease with which they become black or white.
The 30 dots are made black, the points are sequentially assigned to the 14 candidate dots (in this case there are 3), the other candidate dots are set as white, the quantitative evaluation amount of the low frequency component is obtained, and this evaluation amount is compared for each candidate dot. and select 1 candidate dot that gives the optimal value.
Decided to be 4. Candidate tons in Figure 5) (a) to (C)
Of these, the case (C) is shown as an example. Other numbers are determined in exactly the same way. In this way, numbers are assigned so as to always give the optimum image quality, so the image quality will be good no matter how all the dot patterns are arranged.

Note that the location of 1 is free, but if it is close to the edge of the matrix, a false contour may occur, so it is better to set it to the central element of the matrix. There are several possible quantitative evaluation quantities for the low frequency components of dot patterns, but
As a result of experiments, high-quality images can be obtained by following the following evaluation quantities.

First, the dot pattern of rn
≦m1. Q≦y≦n+). Here, let .

The two-dimensional Fourier series 7 Fuv of the dot number pattern f is (where u = 0, 1. . . . , m 1 ; y
==Q, l, , , n-1). Also,
The energy spectrum Euv and the frequency ωuv are Euv = l Fuv 12. It is denoted by rauv =n. As shown in FIG. 5, in order to assign black to the candidate dots and evaluate their low frequency components, an evaluation amount Pi is determined for each candidate dot pattern. PipPi=min
It is indicated by (ωuvlEuv\Q, ωuv\0).

In other words, the lowest frequency for which the energy vector is not 0 is used as the evaluation quantity, and the one with the largest value is determined to be the optimal candidate dot (low frequency components are determined to be weak).
.

FIG. 6 shows an embodiment of the present invention, in which 6 is a gradation recording device, 7
8 is a controller, 9 is a dot number storage memory, 10 is a dot arrangement order storage memory, 11i,
1: buffer memory; 12: recording section;

When the gradation signal 7 is input to the gradation recording device 6, the controller 8 is first activated. Based on the human input signal 7, the corresponding gradation level is determined by the controller 8, and the memory 9 is accessed. The memory 9 stores the number of independent binary dots among the ternary dots of the ternary dot pattern corresponding to each gradation level, and these numbers are read out from the memory 9. Since the memory 10 stores the dot placement order assigned to the matrix elements, the memory 1 is stored in the buffer 11 as a ternary dot pattern under the control of the controller 8 based on the number information read from the memory 9.
They are written in the order they were stored in 0. The ternary information is sent from the buffer 11 to the recording section 12, where gradation image recording is performed.

(5) Description of Effects As explained above, according to the present invention, the elements of the dot pattern matrix are assigned a dot arrangement order that always minimizes the low frequency components of the dot pattern. , it has the advantage of always being able to realize high-quality recording without stripes, twill, roughness, or pseudo limbus.Also, only the dot number configuration of the ternary dot pattern corresponding to each gradation level is memorized. , conventional dots
This method has the advantage that the amount of memory can be reduced compared to a method that stores patterns as they are. Needless to say, the present invention is effective as a multi-level gradation recording method in a device having high recording resolution and capable of expressing several gradations, such as a thermal recording device. For example, it is extremely effective for data communication terminals or facsimile recording units.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the principle of this type of conventional recording processing, Fig. 2 is an example of storing dot patterns in the conventional processing, and Fig. 3
4 is an explanatory diagram explaining the present invention in detail; FIG. 4 is an example of a dot pattern generated according to the process of the present invention; FIG. Figure 6 shows the implementation of the present invention. In the figure, 6T/'i gradation recording device, 7 is input gradation signal, 8
is a controller, 9 is a dot number storage memory, 10 is a dot arrangement order storage memory, 11 is a buffer memory, 1
2 represents a recording section. 1st [2] 2nd (2) Figure 3 Figure 4 Figure 5

Claims (2)

[Claims] (1) Multiple dots correspond to one pixel of a grayscale image,
In the gradation surface single image recording processing method that expresses gradations by changing the areas of the 3 values of white, gray, and black, the arrangement order of 3 value dots is determined for the dot pattern matrix element corresponding to one pixel. In addition to determining and assigning the dots in advance, the number of independent binary dots among the three-value dots of the dot pattern corresponding to each recording density is stored. A gradation image recording processing method characterized in that the stored content is read out, ternary dots are arranged in matrix elements according to the dot arrangement order, and recording is performed. (2) In the assignment to determine the dot placement order to the matrix elements, a black dot is placed on the matrix element for which the order has already been assigned, and a black dot is placed on one of the candidate elements that has not yet been assigned. Place white on
The spatial frequency components of such a binary black and white dot pattern are determined, the lowest frequencies with energy are sequentially compared, the candidate element with the highest value is found, and the 2. The gradation image recording processing method according to claim 1, wherein the allocation is performed by giving the next number after the maximum number determined in the order.