JPS61154270A - Picture processing method - Google Patents

Abstract

PURPOSE:To enlarge and reduce a binarization picture without producing a moire fringe even if the binarization picture has a periodical structure and to make a gradation processing easy by converting the number of picture elements based upon a gradation curve and deciding the density level of each block from the number of converted picture elements. CONSTITUTION:The binarization picture is divided into blocks of appropriate sizes and then the gradation processing is made after counting the number of black picture elements in every block. For example, the number of original black picture elements shown in figure (b) is converted to that of conversion black picture elements shown in figure (c) by using the gradation curve (a). Thus, the density level of every block is decided by the number of conversion black picture elements and the first density matrix pattern is obtained. After the first density matrix pattern is obtained, the second density matrix pattern sizing in proportion to a multiplying facter of an enlargement or reduction is obtained in every block and then the enlarged or reduced scanning is obtained in a block order.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an image processing method that performs at least one of enlarging or reducing an image and gradation processing.

(TY's first support F) Conventionally, methods for enlarging or reducing a binarized image using the pixel density conversion method include the SPC method, the logical sum method, the 9-division method,
Projection methods etc. are known.

(Problems to be Solved by the Invention) Problems with these conventional methods include the fact that the lines are blurred or missing, but the biggest problem is that the systematic dithering method When a halftone image with a fixed phase structure, such as a binarized image, is enlarged or reduced (a), moiré fringes occur.

On the other hand, in the case of this type of binary halftone image, there is no method for easily performing gradation processing (conversion).

The present invention has been made in view of this point, and its purpose is to
It is an object of the present invention to provide an image processing method that can enlarge or reduce even a binarized image with a transparent structure without causing moiré fringes, and can also easily perform gradation processing.

(Means for Solving the Problems) The present invention to solve the above problems (') divides a binarized image into blocks, and for each block, at least one of the Kuroyama series number or the number of white pixels is set to the i'l number. Goru's first step and
The number of pixels is converted based on the gradation curve, the number of pixels of each block is determined from the number of pixels after conversion, and for each block, the first ff1l corresponding to the determined page level is
ll! Using the matrix pattern, a second density matrix pattern of a size corresponding to the enlargement/reduction magnification is
9, and the image reconstructed using the second Fuchimaro matrix pattern is used as the processed image.

(Example) Hereinafter, the image processing method of the present invention will be specifically explained using FIGS. 1 to 7.

First, the 21-ge unification image is the target of image processing.
This binarized gap can be easily obtained by using a dithering I-rix having a size of 4×4 or 8×8, for example 1f1, as a threshold value. The setting width of the threshold value constituting this dither matrix is, for example, 0.1 to
The width is 1.4 culms, and the reflection density is 0.0 for line drawings.
1~0.5Pi! It is preferable to use a fixed threshold value (or use a fixed threshold value).

This is to prevent the image from becoming blank or thick. Also, 11P
Different dither matrices may be used for i-style drawings and line drawings. Note that the binarization method may be a method other than the dither method, such as a density pattern method or a dot method.

In the method of the present invention illustrated in FIG. 1, first, if the image is not a binarized image, the above-mentioned binarization is performed (step 2). Figure 2 1. Dot dispersion type with size 4 x 4 (B
ayer type) dither matrix DM1 (see Figure 2 (a)), the original image A is
(See FIG. 2(B)) is binarized to obtain the binarized image B shown in FIG. 2(C). In this diagram,
The numbers in the dither matrix DM1 and in the original image A are standardized iIJ epilepsy levels, and the pixels in the shaded area of the binarized image B indicate that they are black pixels.

-4=Next, in step (2), the binarized image q; is divided into blocks of appropriate size. In Fig. 2 (c), it is divided into 4×4 sizes. Then, the number of black pixels (or the number of white pixels) in each block is counted (step 2), and the process proceeds to gradation processing. The gradation processing performed here is based on the above black pixel number (hereinafter referred to as the original pixel number) to another black pixel number (one meter lower, this is referred to as the converted black pixel number) based on a predetermined gradation curve.
This is done by converting it into (Step ■). In the example of FIG. 3, t I! is shown in FIG. I! Using the i-tone curve, the original number of black pixels shown in FIG. 3(B) is converted to the converted number of black pixels shown in FIG. 3(C). The type of gradation processing to be performed is determined by the gradation curve used during conversion, but generally, the gradation tune I! with the upwardly convex curve in Figure 4 is used. When ilC is used, the number of black pixels is increased and the number of pixels in high-density areas is increased.When gradation tune MA CB with the downwardly convex curve in Figure 4 is used, the number of black pixels is reduced. This is a conversion that reduces the same number of low m degree parts. Therefore, the R[curve CA is effective for pale binarized images, and the gradation curve CB is effective for darkened images. Of course, it is also possible to use a gradation curve, such as a figure-8 curve, which is a combination of gradation curves CA and CB, and the h gradation curve may be selected to match the desired gradation processing. In an image processing device, three to five types of typical gradation curves are prepared, and one of them can be selected depending on the image.

From the number of converted black pixels obtained in this way, the density level of each block is determined and the first) opening matrix pattern is obtained (step ■). Select a size that is equal to the size (4 x 4 or 8 x 8) of the dither matrix (immediately before the division) used when converting the valued image into 1q, and preferably smaller than +noise of the dither matrix.

If J: is used, high resolution can be maintained while increasing the number of gradations. Figure 5 (B) shows the number of converted black pixels in each block as the normalized average density level of each block, and Figure 5 (C) shows the number of converted black pixels in each block. Based on this, the first density 71 to helix pattern are copied onto each block, and the determination of the first density pattern in this example is based on the ditherer 1 helix DM2 (the same as the ditherer [-lix DM1) described above. 5 (a)) and the density level of each block.

For example, in the case of block 1-1 block SK1, its density level is 11, so the dither matrix r in FIG.
) Of M2, the portion with a density level of 11 or less becomes a black pixel, forming a density matrix pattern such as B1<1 in FIG. 5(C).

After obtaining this first 'a' matrix pattern, a second density matrix pattern of a size corresponding to the enlargement/reduction magnification is obtained for each block (step plane), and these are arranged in block order as enlarged/reduced images. Determine (step ■).

Figure 6 (a) is thus 1! 'I magnification factor 5
, / /l, and FIG. 6(b) is a reduced image with a reduction magnification of 3/7I.

Here, the first. The size ratio of the second matrix pattern is according to the vertical and horizontal expansion/reduction magnification.
The vertical and horizontal size of the 'aI'ct' matrix pattern is the vertical and horizontal size of the first density matrix pattern multiplied by the vertical and horizontal expansion/reduction magnification. Therefore, in the example of FIG. 6, the size is 5×5 in FIG. 6(a), and 3×3 in FIG. 6(b).

In this example, when the R1 pattern obtained by two-dimensionally arranging the corresponding patterns in the first density matrix pattern is divided by the size of the second density matrix pattern, The second t
ttlrcf, a pattern having the same positional relationship as the matrix pattern is extracted and used as the corresponding second density matrix pattern. FIG. 7 is an explanatory diagram showing an example of obtaining the second mlα matrix pattern from the first density matrix pattern (magnification: 5/
4), the first density matrix pattern (size is 4)
×4) block f11. f12. f13+・1. , f
21+'22+...,..., the second Kanmaro matrix pattern is a block F++・F121 Ft3+-, F;) I, F=8- 22,・. . . indicates a partitioned state. First, block [second i11 degree matrix corresponding to violet 1] [all blocks 1 as a matrix pattern] check rllllrl?
.

f13. ..., f21+f22+...,...,
A pattern at the position of block F++ is cut out from a mother pattern that is assumed to contain the same first density matrix pattern corresponding to block f I '1. Similarly, the block “Zuro 2nd equivalent to 12”
The am matrix pattern for all blocks f1
1+'+2+ f13+"'+f21, f22...
, . . . , a pattern at the position of block F12 is cut out from a mother pattern that is assumed to contain the same first density matrix pattern corresponding to block f12. That is, the second art matrix pattern corresponding to block Fi,i is all blocks f11, f12, r+3, °°°, "21, '22
+'...

... is assumed to contain the same first density matrix pattern corresponding to block fij. A pattern at the position of block "ij" is cut out from the mother pattern. ) is the second density matrix pattern obtained in this way arranged on a plane. The same applies to FIG. 6(b).

Incidentally, the matrices DM1 and DM2 do not need to be made of the same material; for example, the matrix DM2 may be of a dot concentrated type (spiral type).

Also, the specific method for obtaining the pattern of each block after scaling of the previous item is to actually configure the mother pattern of the previous item in memory, read data at a predetermined address from it, and obtain the pattern. However, this would require an extremely large memory capacity. In this case, instead of actually creating a mother pattern, you can pay attention to the periodicity of the pattern and calculate the density of each pixel in the following manner to obtain the pattern after scaling.

That is, in the case of expansion (i) rate m7n>, the x-th pattern in the first block in the row direction of the new block (block after expansion) is the same as the pattern in the first block in the row direction of the block before expansion. , ΔD1=mod [x 4−
mod [(T-1) (m-n>.

nko 1-2. The pattern in the y-th column in the JIS-th block in the column direction of the new block, which is equal to the pattern in the JIS-th row of the new block, is AD2=morl [y + mod [LJ-1)
(m-n).

n]+1-2. equal to the pattern in the n 1+1th column, while reduced (magnification IIl/r
In case l), a new block (block after reduction)
The x-th pattern in the Tffi-th block in the row direction is AD1=mod [X + morl [(T-1)] in the TI-th block in the row direction before reduction.
(n −', n−ml > , n
]+1-2. The pattern in the y-th column in the 8th block in the column direction of the new block, which is equal to the pattern in the n + 1st row, is in the 8th block in the column direction of the block before reduction.

AD2=mod [y +mod [(J-1>
(n −1n-Inl), n co + 1-2.
n ] + equal to the pattern in the first column.

Here, mod[l'1. Q] is the remainder of p÷q,
Of course it is smaller than q.

Therefore, the pixels of each block before scaling? Once stored in memory, a new block pattern can be easily obtained by using ADI and AD2 as addresses in the row and column direction and reading out the pixel density in the corresponding block before scaling. I can do it.

(Effects of the Invention) As explained above, in the present invention, a second density matrix pattern of a size corresponding to the magnification is obtained for each block from the first density matrix pattern.
The halftone dot pitch remains unchanged, and unlike the conventional method of obtaining enlarged/reduced images by changing the sampling interval, moiré fringes are less likely to occur. Furthermore, since gradation processing is achieved by converting the average density level (number of black pixels) of a block, gradation processing can be easily performed.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing an example of the method of the present invention;
The figure is an explanatory diagram showing an example of the binarization in Fig. 1, Fig. 3 is an explanatory diagram of the gradation processing in Fig. 1, Fig. 4 is an explanatory diagram of the gradation curve, and Fig. 5 is an explanatory diagram of the gradation process in Fig. 1. FIG. 6 is an explanatory diagram of the second density matrix pattern (enlarged/reduced image i>) in FIG. 1, and FIG. 7 is an explanatory diagram of the first density matrix pattern to the second density matrix pattern. It is an explanatory diagram of a method of obtaining a matrix pattern.DMl, DM2...Dither matrix A...Original image B...Binarized image f11.f12."'
, f2+・f 22 , ”'...Block F11.F12...1F of the first ma matrix pattern
21. F22. ...Second density matrix pattern blocks CA, CB...Tone curve Patent applicant Roku Konishi Photo Industry Co., Ltd. Agent Patent attorney Fuji Ijima 1 person 1N Kai 11U61-154270 ( 6) Kite diagram 4 A: Hoisting diagram

Claims (4)

[Claims] (1) A first step of dividing the binarized image into blocks and counting at least one of the number of black pixels or the number of white pixels for each block, converting the number of pixels based on the gradation curve, and after the conversion The density level of each block is determined from the number of pixels, and for each block, a second density matrix of a size corresponding to the enlargement/reduction magnification is created using the first density matrix pattern corresponding to the determined density level. and a second step of obtaining a pattern, and an image reconstructed using the second density matrix pattern is used as a processed image. (2) The first density matrix pattern is characterized in that a pattern determined by a comparison between a threshold group used to obtain a binarized image to be subjected to image processing and the determined density level is used as the first density matrix pattern. An image processing method according to claim 1. (3) Image processing according to claim 1 or 2, characterized in that the size of the block is selected to be less than or equal to the size of the threshold group used when obtaining the binarized image that is the object of image processing. Method. (4) When the mother pattern obtained by two-dimensionally arranging the corresponding patterns in the first density matrix pattern is divided by the size of the second density matrix pattern, Claim 1, 2, or 3 is characterized in that a pattern having the same positional relationship as the second density matrix pattern is cut out and used as the corresponding second density matrix pattern. image processing method.