JPS60130263A - Intermediate tone picture processing method - Google Patents

Abstract

PURPOSE:To improve the resolution of gradation by sectioning a picture prescribed area into small areas, identifying the density of a light, intermediate and dark area in response to the density data of each small area so as to specify a matric pattern group. CONSTITUTION:A gradation data is fed from a picture reader 400 or a host 200 to an intermediate data processing unit 100. A central controller 10 writes a matrix pattern stored in an ROM and when all matrix patterns are stored in the RAM, the density area is identified by the gradation data, the matrix pattern is specified and read from the RAM. The matrix pattern data are three kinds of an original pattern A including 8X8 data (light part), an original part), an original pattern B (intermediate part) using 4X4 data as one block and comprising four blocks and an original pattern C (dark part) using 2X2 data as one block and comprising 16 blocks.

Description

[Detailed Description of the Invention] ■Technical Field The present invention relates to image information processing of halftone images such as photographs and paintings, and in particular to obtaining pitch distribution pattern data that represents a halftone image from tone data. Related to gradation information processing.

This type of image information processing is performed in fields where images containing halftones, such as photographs and paintings, are output as hard copies, such as facsimiles, digital copiers, image file and transmission terminals, and video plotters.

■Conventional technology One of the gradation information processing methods is recording with a predetermined number of bits (
Display) From among multiple halftone matrix patterns in which information bits are distributed in a predetermined manner, one that corresponds to the density indicated by the gradation data is identified (selected) and the bit information is used as the gradation data. in correspondence with the position on the record (display) of
There is a fixed density pattern method that is developed in page memory or buffer memory.

In this case, the density usually corresponds to the number of pixels (bit number) in the matrix, so if the number of gradations for one expression is increased, the matrix itself becomes larger, and one gradation data is used for one matrix. The drawback is that the resolution is reduced because the risks are removed.

When the matrix is made smaller, the resolution becomes higher, but the number of expressed gradations becomes smaller, which has the disadvantage that the smoothness of intermediate tones decreases.

Therefore, in the past, a method has been proposed for obtaining image information by changing the size of a matrix depending on the roughness of the image (for example, Japanese Patent Laid-Open No. 159173/1982).

However, in this case, there is a problem that the amount of fixed memory data becomes enormous due to the accuracy and complexity of determining the roughness of the image and the need to prepare many different types of matrices.

In addition, multiple different types (4 types) of small matrix patterns (
4 pixels = 5 gradations) to form one large matrix pattern (4 types x 4 pixels = 16 pixels: 4 types x 5 gradations = 20 gradations), and a small matrix pattern for each type, within the large matrix pattern. A gradation information processing method has been proposed in which image information is obtained in units of small matrix patterns by fixing the position of , and allocating gradation data to a specific type of small matrix helix pattern from the arrangement order on the image (for example, Japanese Unexamined Patent Publication 1987-
159174).

According to this, the image information of one large matrix pattern is composed of the image information of a plurality of types (four types) of small matrix patterns. In other words, one large matrix pattern is specified using a plurality of (four) pieces of gradation data.

However, this only means that the image information of the large matrix pattern is determined by each of multiple types (4 types) of small matrix patterns, that is, the large matrix pattern is determined by multiple (4) pieces of gradation data; The matrix pattern essentially determines the resolution and gradation smoothness, and the improvement in smoothness by a large matrix pattern is small. In other words, since small matrix patterns of the same type appear at predetermined intervals (every other small matrix pattern), the essential problem of dithering remains that irregular or regular patterns appear in the reproduced image. , a large matrix pattern is similar to the matrix pattern of the conventional dither method in which multiple regions are regarded as one section, and the smoothness of gradation cannot be expected much from this.

Furthermore, since the density characteristics differ for each matrix pattern group, it has been proposed to provide multiple groups of matrix patterns with different density characteristics to record halftone images with different density characteristics (for example, Japanese Patent Application Laid-Open No. 1983-1989-1) 6
6970), but in any case, each group
Since it is not possible to obtain more tones than the number of dots included in the matrix pattern, even if several groups of characteristics are provided, the smoothness of the tones is insufficient and the density characteristics are also rough. There is.

In addition to the above, there is also image information processing that performs density modulation, single area modulation, etc. of recording dots according to gradation data (for example, Japanese Patent Application Laid-Open Nos. 51-123510, 1982-1791).
．． No. 9, JP-A-54-115254, and JP-A-55-222781) have a limited number of multilevels (number of gradations), and therefore may not have enough gradations depending on the application.

There are also methods that use density modulation of recording dots, single area modulation, and density pattern (matrix pattern) in combination (for example, Japanese Patent Laid-Open No. 54-36736, Japanese Patent Laid-Open No. 54-7
3650, Japanese Unexamined Patent Publication No. 57-76559),
Since the density pattern is fixed, gradation is given priority within the limited number of gradations, and resolution cannot be emphasized.

■Purpose The purpose of the present invention is to improve gradation and resolution, and more specifically, to automatically adjust gradations from gradation priority to resolution priority within the same target image according to the density of each part of the image. The purpose of this study is to display natural expressions in reproduced images by selecting appropriate characteristics and resolutions.

■Structure In order to achieve the above object, in the present invention, in accordance with a plurality of predetermined density data, each of which indicates the density of a predetermined small area of an image, the image density of the entire area to which these density data are allocated is calculated at least. identify a density region of three or more classifications; specify a matrix pattern group of a predetermined size in the identified density region from at least two or more sizes; specifying one matrix pattern of the identified matrix pattern group with the number of density data corresponding to the size; obtaining information on this specified one matrix pattern as image information associated with the number of density data corresponding to the size; .

Next, a specific example will be shown and explained.

As shown in FIG. 1, a predetermined area of the image is divided into small areas
0) ~ It shall be recorded or displayed by allocating 4 dots.

Then, the density of the recording or display surface area (predetermined area) assigned to X(0) to X(15) is determined based on these density data
(0) to , in the case of the middle part, 4×
4, in the case of the dark area, a 2×2 square helix pattern group is specified.

In the case of bright areas, density data x
Assuming that (o) to (indicates o to 64), one matrix pattern of the 8×8 matrix pattern group (65 types) is specified, and the white 2 black (“0”, rl”) bit distribution of this pattern is calculated using the density data
The area (0) to X (15) (FIG. 1) is extracted as image information to be assigned to image reproduction (FIG. 2a).

In the case of the middle part, a 4 x 4 matrix pattern group is specified, so as shown in Fig. 2b, four 4 x 4 matrix pattern groups A-D are used as density data
(0) to X (15) (as shown in Figure 1), 4XJ
The I matrix pattern group (17 types) is specified, and C is Σ It is assumed that D is specified from among the risk pattern groups (17 types).

In the case of dark areas, 2×2 matrix pattern groups are specified, so as shown in FIG. In order to allocate the area of X (15) (Fig. 1) to the image reproduction, A is
)/4 density data (indicating 0 to 4) is specified from the 2×2 matrix pattern group (5 types), and B is X (])/4 density data (indicating 0 to 4). It is assumed that the 2×2 matrix pattern group (5 types) is specified from among the 2×2 matrix pattern groups (5 types) with the concentration data of Cl:j:X (4)/4 (indicating θ~4). In the same way, P is the density data (indicating 0 to 4) of shall be specified from.

According to this, an image is reproduced in a large matrix pattern with a large number of gradations in bright areas to express natural gradations, and in dark areas, for example, outlines and illustration lines are reproduced.

For parts such as characters, the image is reproduced using a small matrix pattern with high resolution, and parts such as outlines and nine characters with illustration lines are clearly expressed. The intermediate portion contains both gradation and resolution appropriately.

When measuring the histogram for each pattern in an image, it is found that there is a difference in density distribution within a single image between a photographic image containing many intermediate tones and a white/black binary image. The density of white and black binary images is biased toward low and high levels, and resolution is required not only for white and black binary images but also for general photographic images.

It was found that images with high spatial frequencies have a skewed density distribution.

In the present invention, the density distribution is biased in this way, and both high resolution and multiple gradations can be appropriately expressed.

Note that in the above specific example, the concentration data X(0) to X
, (15), 4 dots are assigned to each of them, but 1 dot 1- can also be assigned, or 8 or more dots can be assigned.

Next, another example in which the density pattern matrix size is made to correspond from large to small in the direction from the brightest region to the darkest region will be described with reference to FIGS. 3a to 3c. In this example, in the dark area, the area of density data X(0) to X(15) (
Four matrices are used to reproduce the image in Figure 1), and in the middle part, as shown in Figure 3b, a 3x3 matrix is used to reproduce the image of the area of density data X (0) to X (15) (Figure 1). For reproduction, one matrix and one fraction of 7 dots I- are used, and in the bright area, one matrix is used as a 4×4 matrix as shown in FIG. 3a.

Note that the numbers in the matrix in Figures 3a to 3C are pattern data (white "0", black "1" distribution data to pip 1)
This is the comparison value (reference data) used when creating a matrix, and the calculated value whose formula is shown outside the matrix is compared with the comparison value, and the second dot (number position) is marked in black. 1"
is assigned as image information. In this example, image reproduction of the area of density data X(0) to X(15) (FIG. 1) is performed using 4.times.4 dots. Figures 2a to 2C above
In the example shown in the figure, 8×8 dots are used.

In addition, in Fig. 3b, the outside of the matrix (3 dots)
is the concentration data X (5) , X (7) and X (
13) (data for 3 x 3 matrix) divided by 16 to align the gradation digits.
The 3 bits in the leftmost column of the matrix are the 3 bits in the leftmost column of the matrix, and the 3 left squares (3 dots) in the bottommost column of the matrix are density data X (10)
, X (11) and X (14) times 3 (3×3
1-matrix worth of data) to align the gradation digits.
It is defined as the 3 bits in the bottom column of the 3×3 matrix specified by the value divided by 6, and the 1 square in the bottom column in the rightmost column of the matrix (
1 dot) is 9 times (3 x 3
16 to align the gradation digits (matrix data)
The 1 bit in the leftmost column and the lowest column of the 3×3 matrix is specified by the value divided by .

Next, an example in which the density pattern matrix size is made to correspond from large to small in the direction from the intermediate region to the brightest and darkest regions will be described with reference to FIGS. 4a to 4c. In this example, in the dark area, four matrices are used to reproduce the image in the area of density data X(0) to As shown in Figure 4b, 1 matrix is used to reproduce the image of the area (Figure 1) of density data X(0) to Similarly to the dark area, 4 matrices are used as 2×2 matrices.

Note that the numbers in the matrix in FIGS. 3a to 3C are as described above (description with reference to FIGS. 3a to 3C).

Next, the density divisions determined by the density data X(0) to A case will be explained in which binary white and black are expressed without halftone modulation. The darkest part (dark part in this example) is shown in Figures 5a to 5C.
This shows the case where the image is expressed in two values, white and black, without halftone modulation. In this example, in the bright area, four 71-lixes are used to reproduce the image of the area (Fig. 1) with density data X (0) = X (+5) as a 2 × 2 matrix as shown in Fig. 5a, In the middle part, as shown in Fig. 5b, the area of density data X(0) to X(15) is formed as a 4x4 matrix (Fig. 1).
1 matrix is used for image reconstruction 1, and in dark areas, each of the density data X(0) to Obtain conversion data. As a result, image information that emphasizes the resolution of each small area in the dark area can be obtained.

Next, in a mode of use in which image information is provided to a recording or display system in which the dot density and/or area (size) of recording or display can be controlled, modulation of the dot density and/or area can also be combined.

For example, when giving image information to a recording system that can control the dot area, the density data
-X (15) Determine the dot area for image reproduction in the region (8×81 dots 1 in the embodiments of FIGS. 2a to 2b, and 4×4 dots in the embodiments of FIGS. 3a to 5c).

In addition, for each specified size, based on the density data assigned to the size, one matrix is reported from the matrix group of the size, and at the same time, the area of the recording area of the size is calculated. may be determined. For example, in the case of FIG. 2a, the recording dot area of an 8×8 matrix is determined by ΣX (n)/4, and in the case of FIG. 2b, the matrix area is determined by ΣX(n). In the case of Figure 2c, at X (0)/4, B at X (1)/4
Determine the recording drum 1 area of C by X (4)/4.

The same applies below.

In any of the examples explained above, the density data
When the sum of 0) to X, (15) is the highest value (16X 16), that is, when the density of the area X(0) to
The image information is reproduced with the entire reproduction area of (15) as black "]", and when the sum of density data X (0) to X (15) is the lowest value (16X O), that is, area X (0) ~
When the density of X (15) is the lowest, it is preferable to reproduce the image information by setting the entire reproduction area of density data X (0) to X (15) as white "0" without drawing the matrix, because the processing speed is fast. .

According to the present invention described above, a halftone pattern that can produce a large amount of gradation is automatically selected in areas where smooth gradation is required, and a high tone pattern is automatically selected in areas where high resolution is required. Patterns and cross-binary data that provide resolution are automatically selected, and smooth midtones and high resolution are appropriately expressed, resulting in a near-natural expression. Furthermore, since the pattern is not unnecessarily reduced in size, the processing speed is correspondingly high.

Next, the present invention will be explained in detail.

FIG. 6 conceptually shows an apparatus configuration for implementing one embodiment of the present invention.

This device configuration includes an image reading device 400 or a host 20 such as a computer or a facsimile device (halftone reception).
0, to gradation data [density data X (0) to X (15
)] is shown as a halftone data processing device 100 that develops image information on the page memory 2O in a pip 1-(pip 1) distribution.

The halftone data processing device 100 is actually connected to the computer unit 1, and does not have a block configuration as shown in the figure, but for ease of understanding, the internal elements of the computer unit 1 are shown as a central control unit that is the main body of the computer. 10
It is more separated and shown in the form of a single piece of hardware.

Gradation data is sent from the image reading device 400 or the host I-200 to the halftone data processing device 10O.

Halftone data processing device 1. The central control unit 10 of the OO stores the matrix pattern (in this example, matrix data in which comparison values are stored) stored in the ROM in the RAM.
(original pattern memories 30Δ to 30C) and memorize all matrix patterns in RAM, after that,
The density area is identified using the gradation data given from the reading device or the host, and the matrix pattern is specified and read out from the RAM.

Here, the matrix pattern stored in the RAM will be explained. In this embodiment, a predetermined area (Fig. 1) specified by density data X (0) to In the manner shown, image information of 8×8 dots (1 dot 1 bit) is allocated and obtained. The matrix pattern data includes 8 x 8 matrix groups (gradations 1 to 6) assigned to bright areas.
Original pattern A containing 8x8 data (comparison value data is distributed as shown in Figure 7a) for creating 64 patterns of 4), 4x4 matrix group assigned to the middle part (
4× to create 16 patterns of gradations 1 to 16)
Original pattern B (which contains 8x8 data in which 4 pieces of data are 1 block and 4 blocks of the same data are lined up)
The comparison value data is shown in Figure 7b), and the same 2x2 data is used as one block to create a 2x2 matrix group (4 patterns of gradations 1 to 4) assigned to the dark area. There are three types of original patterns C including 16 pieces of 8x8 data arranged in original pattern memory 30A, 30B and 30C (all RAM).
write to. Note that the reason why both original pattern memories have the same number of data is because of the image information generation described later.
- This is to obtain information on the 8x8 dot configuration.

Next, the operation of the halftone data processing apparatus 100 will be explained based on the block configuration shown in FIG. Figures 8a to 8f show data processing operations of the central controller 10.

Referring first to FIG. 8a. Proceeding to the gradation data processing, the central control unit 10 stores a horizontal direction (main scanning direction) input data address counter S I-1, a same direction output data address counter PH, and a vertical direction (sub scanning direction) input data address counter S and same-direction output data address counter PV are set to 1, respectively, and the data is read.

If the read data indicates the end (end of page), the process returns to the main routine. If the read data indicates LF (line feed), the input data address counter Sv is counted up by 4 (predetermined area bones), and the output data address counter P is counted up by 8 (predetermined area bones). As shown in Figure 1, the input data is 4
×4 pieces (16 small areas) are considered as the prescribed bone area, so
The input data line feed corresponds to a predetermined bone area, that is, four small areas. Also, as shown in Figures 2a to 2c,
Since the output data is 8.times.8 dots (64 dots 1 to 1) as the predetermined region bone, the line feed of the output data is the predetermined region bone, that is, 8 dots.

If the read data indicates CR (carriage return: return to the beginning in the main scanning direction), both the input address counter SH and the output address counter PR are reset to 1.

Now, the read data is density data, and when this is taken in for a predetermined area bone [X (0) to X (15)), the density a of this predetermined area is calculated.

a=ΣX(n). Note that X(O) to X (15) are respectively 0 to
It shows 16 gradations, and at the highest density of all black, a =
16X16=256, at the lowest density of all white, a=
16XO=O.

Next, refer to a, and if it is O (margin), proceed to full white writing (FIG. 8b). When a is 16X]6 or more (all black), proceed to all black writing (FIG. 8c).

When it is neither completely white nor completely black, a is the dark area discrimination value V r
1, if a is greater than this, it is assumed that the entire density of the predetermined area is dark, and the process proceeds to dark area writing (Fig. 8d).
Compare a with the bright area discrimination value Vr2, and if a is less than this value, the entire density of the predetermined area is determined to be bright, and bright area writing (Fig. 8e) is performed. When a is less than Vr1 and exceeds Vrl, It is assumed that the entire density of the predetermined area is intermediate, and the process proceeds to intermediate area writing.

When these stores are completed, that is, the concentration data
) to X(15) worth of image information (8×8 dots 1-) is obtained and written into the page memory 20, the process returns to data reading and the process described above is followed.

Next, all white writing will be explained with reference to FIG. 8b.

When proceeding to all-white writing, the central control unit 10 sets all the pins 1 to 1 of the pattern memory (RAM) 121 having an 8x8 dot configuration to "0", and transfers the data of this pattern memory 121 to the output address counter P4 of the page memory 2O. (
, PV is written in the area specified by the value of PV, the contents of the output address counters SH and PH are incremented by 4 and 8, respectively, and the process returns to data reading in FIG. 8a. As a result, all white rOJ is written in the 8×8 dot 1 to area of the page memory 20.

Next, all black writing will be explained with reference to FIG. 8c.

When proceeding to all-black writing, the central control unit 10 sets all bits of the pattern memory 121 to [1] and transfers the data of this pattern memory 121 to the area of the page memory 20 specified by the values of the output address counters PH and PV. write to,
Then, the contents of the output address counters SH and PI are incremented by 4 and 8, respectively, and the process returns to the data reading of FIG. 8a.

As a result, all black "1" is written in the 8.times.8 dot area of the page memory 20.

Next, dark area writing will be explained with reference to FIG. 8d.

When proceeding to dark area writing, the central controller 10 first writes the 77X
Counters H (vertical direction) and L (horizontal direction) that define the data read address of pattern 3 (30G) and the write address of pattern memory 121 are each set to 1. After that, first, the comparison value data 5DHL (H is the content of counter H, L is the content of counter L) of the original pattern 30C (Fig. 7c) is read out, and the density data ( X in A block
(0), X (1) in B block, X (4) in C block...see Figure 2c) and 5D8L, and if the density data is greater than or equal to S D HL, the pattern memory 121, which is determined by the contents of the counters H and L, is memorized as "1": black, and when the density data is less than 5DHL, rOJ is memorized. When this is completed for one piece of comparison data 5DHL, the counter L is incremented by 1, and the next comparison data SDI-1L is read out and data is written to the same pin 1.

When this is done eight times, the counter H is incremented by one and the same process is executed. Harano (turn 30G 8×8
If this is done for each piece of data (FIG. 7C), image information of an 8×8 dot distribution will be written in the pattern memory 121. The data of this pattern memory 121 is transferred to the output address counter PH of the page memory 20.
, PV, and increments the contents of the input and output address counters SL (, PH by 4 and 8, respectively), and returns to the data reading in FIG. 8a.

As a result, in the 8×8 dot area of the page memory 20,
This means that image information for 16 2×2 matrixes has been written. The resolution is determined by this 2×2 matrix.

Next, bright area writing will be explained with reference to FIG. 8e.

When proceeding to the bright area writing, the central controller 10 first sets the counter H which determines the data read address of the original pattern 1 (3OA) and the write address of the pattern memory 121.
(vertical direction) and L (horizontal direction) are each set to 1. After that, first read out the comparison value data 5DI-1L (H is the content of counter H, L is the content of counter L) of the original pattern 30A (Fig. 7a), and compare it with the overall density a=ΣX (n)/4. However, if the overall density a is SD, 11 or more, "1" is stored in the pin determined by the contents of the counters H and L in the pattern memory 121, and "1: black" is stored when a is less than SD HL. 0" is stored in memory. When this is completed for one comparison data S D HL, the counter L is incremented by one, and the next comparison data S D HL is read out and similar bit data writing is performed. This is 8
When the process is repeated, the counter H is incremented by 1 and the same process is executed.

If this is done for 8×8 data of the original pattern 3OΔ (FIG. 7a), image information of an 8×8 dot distribution will be written in the pattern memory 121. The data of this pattern memory 121 is written and input into the area of the page memory 20 specified by the values of the output address counters PH and PV.

The contents of the output address counters SH and PH are incremented by 4 and 8, respectively, and the process returns to data reading in FIG. 8a. As a result, the 8×8 dot 1 of the page memory 20
This means that image information for one 8×8 matrix has been written in the - area. The gradation is smooth and determined by the number of 65 gradations expressed in this 8×8 matrix.

Next, intermediate section writing will be explained with reference to FIG. 8f. When proceeding to the intermediate part writing, the central control unit 10 first sets the counter H (which determines the data read address of the original pattern 2 (30B) and the write address of the pattern memory 121).
Set 1 to each of L (vertical direction) and L (horizontal direction). After that, first, the comparison value data SDHL (H is the content of counter II, L is the content of counter L) of the original pattern 30B (Fig. 7b) is read out, and the density data of blocks A-D to which this data is associated is read out. Japanese (A Bron 20
(see figure) and S D HL, and if the sum ΣX(n) of the density data is 5 DHL or more, the pattern memory 12. "1" to the pin 1 determined by the contents of the counters H and L: Black is memorized and the density data is S D HL
If it is less than 0, "0" is stored. When this is completed for one comparison data 5DHL, the counter L is set to 1.
It increments, reads out the primary comparison data 5DHL, and writes similar data. When this is done eight times, the counter 1 is incremented by one and the same process is executed.

If this is done for the 8.times.8 data of the original pattern 30B (FIG. 7b), image information of an 8.times.8 dot 1-distribution will be written in the pattern memory 21. The data in the pattern memory 21 is written to the area of the page memory 20 specified by the values of the output address counters PH and PV.

The contents of output address counters SH and PI-1 are incremented by 4 and 8, respectively, and the process returns to data reading in FIG. 8a. As a result, image information for four 4x4 printers is written in the 8x8 dot area of the page memory 20. The gradation is 17 gradations determined by this 4×4 matrix, and the resolution is also determined by the 4×4 matrix. It will be in the middle.

In the configuration of FIG. 6 referred to in the above explanation, the buffer memories 121 to 123 actually correspond to the internal RAM or external RAM of the computer, and the page memory 2
0 is an external RAM, and memories 30A to 30C in which original patterns 1 to 3 are temporarily stored are internal RAMs of the computer.
Or external RAM. In this example, Figures 7a to 7c
The original data 1 to the risk pattern comparison data shown in the figure are stored in the internal ROM or external R, OM of the computer. Other goo 1 to G1 to G3 + adder ADD.

Comparators CMPI, etc. correspond to functions performed inside the computer.

Note that in the above description, original pattern 1 having threshold data
3 (Figures 7a to 7c) to form a matrix pattern, the matrix pattern in which the image information Pino I- is distributed is stored in advance in ROM or RAM, and the density data ( One matrix pattern may be selected using data compared with SDI-1L. In this case, the amount of memory for holding the matrix pattern increases.

FIG. 9 shows an outline of the actual configuration of the data processing apparatus 100 shown in FIG. 6. The processing program is CPU board 10
The data tables 71 to 71 to reference in creating the pattern (FIGS. 7a to 7c) are stored in the ROM of the pattern board 30. Commands and density data from the host 200 are input from the input interface 41 of the interface board 40, and when the CPU 10 completes the halftone bit image development as a result of determination and processing, the bit image is developed in the page memory 20. The bit image data on the page memory 20 is transferred to the D on the interface board 40.
By the operation of the MA controller 1 roller 43, the bit 1 image is outputted to the plotter 300 via the output interface 42, and the bit 1 image is recorded on the printer 1 to paper.

[Brief explanation of drawings]

FIG. 1 is a plan view showing the image-corresponding distribution of density data obtained by reading an image. FIGS. 2a to 2C show a matrix (turn section) corresponding to reproduced image information in one embodiment of the present invention;
Figure a shows the image reproduction driver 1 distribution (ma 1
Fig. 2B is a plan view showing the Mad IJ pattern when the entire density is medium, and Fig. 2C is a plan view showing the Mad IJ pattern when the entire density is medium.
FIGS. 3a to 3C are plan views showing matrix nos. (turns) corresponding to reproduced image information in another embodiment of the present invention; FIG. Diagram: Indicated concentration data X(0) to X
(15) A plan view showing the comparison value for image reproduction (ratio for matrix pattern formation! bite data) when the whole is in bright density, and Figure 2b is when the whole force is at till density in 1,
FIG. 20 is a plan view showing comparative data when the whole is dark density. 4a to 4c show matrix pattern divisions corresponding to reproduced image information in another embodiment of the present invention,
FIG. 4a shows the concentration data X(0) to X(1
5) A plan view showing comparative values for image reproduction (comparative data for matrix pattern formation) when the whole has a bright density, and Figure 4b shows a plan view showing comparative data when the whole has an intermediate density. Figure 2c is a plan view showing comparative data when the entire area is dark density. 5a and 5C show matrix pattern divisions corresponding to reproduced image information in another embodiment of the present invention, and FIG. 5a shows density data X(0) to X (15
) Comparison value for image reproduction when the entire image is bright density (ma1
Fig. 5b is a plan view showing comparison data when the entire density is medium, and Fig. 5c is a plan view showing the comparison data when the entire density is dark.
- It is a plan view showing risk pattern divisions. FIG. 6 is a block diagram conceptually showing the configuration of an apparatus for carrying out one aspect of the present invention, and FIGS. 7a, 7b, and 7C show comparison data stored in original pattern memories 3OA, 30B, and 30C. FIG. 3 is a plan view showing the distribution. Chapter 8a
8B, FIG. 8C, FIG. 8D, FIG. 8E, and FIG. 8F are flowcharts showing the gradation data processing operation of the central controller 10. FIG. 9 is a block diagram showing an outline of the actual device configuration.

Claims (8)

[Claims] (1) In accordance with a predetermined plurality of density data, each of which indicates the density of a predetermined small area of the image, the image density of the entire area to which these density data are assigned is identified into at least three or more density areas; specifying a matrix pattern group of a predetermined size in the identified density region from two or more sizes; A halftone image processing method: specifying one matrix pattern of a pattern group; obtaining information on the specified one matrix pattern as image information associated with a number of density data corresponding to the size; (2) The halftone image processing method according to claim (1), wherein there are three or more sizes, one of which corresponds to each density area. (3) The size is graded from large to small according to those allocated to low concentration areas to those allocated to high concentration areas,
A halftone image processing method according to claim (2). (4) The size according to claim 1 or 2, wherein the size is gradually large to small according to the size assigned to the intermediate concentration to the high concentration and the low concentration.
The halftone image processing method described in . (5) Image information of an area assigned to the predetermined plurality of density data, where the density determined by the predetermined plurality of density data is at least one of the highest and the lowest. Claim (1), obtained as binary image information of at least one of the whole heat and the whole mill, respectively;
The halftone image processing method according to item (2) or item (3). (6) Claim (1) wherein at least one of the highest and lowest image densities of the entire area to which the predetermined plurality of density data are allocated obtains image information obtained by binarizing the density data. , the halftone image processing method according to item (2) or item (3). (7) According to the predetermined plurality of density data, at least one of the image reproduction dot density and the dot area of the area to which these density data are allocated is determined. The halftone image processing method according to item (2) or item (3). (8) According to the number of density data corresponding to the size, at least one of the image reproduction dot density and the dot area of the area to which these density data are allocated is determined, The halftone image processing method according to item (2) or item (3).