JPS61194972A - Method of enlargement/reduction of image - Google Patents

Abstract

PURPOSE:To eliminate moire fringes without changing grid spacings by obtaining in every block the second density matrix pattern of a size depending on the magnification from the first density matrix pattern. CONSTITUTION:Diagram is an example with an enlargement magnification of 5/4. Blocks f11, f12..., f21, f22..., ... consisting of the first density matrix patterns (4X4 in size) on a plane are rearranged into blocks F11, F12..., F21, F22..., ... consisting of the second density matrix patterns (5X5 in size). As the second density matrix patterns corresponding to block Fij, patterns lying in block Fij are cut out from the plane containing all of the virtual first density matrix patterns in blocks f11, f12..., f21, f22..., ... containing fij.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an image enlarging/reducing method for at least one of enlarging or reducing an image.

(Prior Art) As image enlargement/reduction methods for enlarging or reducing an image using a pixel density conversion method, the simple thinning method, the SPC method, the OR method, the 9-division method, the projection method, and the like are conventionally known.

(Problems to be Solved by the Invention) Such a method is used in printers, facsimiles, etc., and is mainly known as a method for enlarging/reducing line drawings and character drawings. When these methods are applied to an image with gradation, the magnification is an integer multiple, and the mesh pitch of the image after scaling is usually different. Also, when multiplying by a rational number, image deterioration (moiré fringes) occurs,
There was a problem in that an image that could not be put to practical use was created.

The present invention has been made in view of the above-mentioned problems, and its purpose is to make it possible to keep the screen pitch unchanged before and after enlargement/reduction, and to be able to perform enlargement/reduction by a rational number of times without causing image deterioration. The object of the present invention is to provide a method for enlarging/reducing images.

(Means for Solving the Problems) The present invention to solve the above problems divides a binarized image into unit areas, forms divided areas with a predetermined number of adjacent medium areas, and blacks within the unit area. For partitioned areas with small variations in the number of pixels, a large-sized density matrix pattern is used to determine the black pixel arrangement, and for partitioned areas with large variations in the number of black pixels within a unit area, a small-sized density matrix pattern is used. First, the black pixel array is divided into a plurality of blocks, and for each block, a mother pattern is assumed in which the pattern is arranged two-dimensionally, and the mother pattern is enlarged/reduced by It is characterized by cutting out a pattern that has the same positional relationship when partitioning the block in a size corresponding to the block size, and using the pattern as a new pattern for each block to obtain a reconstructed image as an enlarged/reduced image. It is something.

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

Here, the binary image to be enlarged/reduced is usually one obtained using a dither method, an 11 degree pattern method, a halftone method, or the like. In the method of the present invention illustrated in FIG. 1, a dot dispersion type (Q ay
The 21i image shown in Figure 2 (c) is obtained by binarizing the original image A (see Figure 2 (b)) by the dithering method using a dither matrix (see Figure 2 (a)) of the er type). Assume that B is given as an object to be enlarged or reduced. In FIG. 2, the numbers in the dither matrix and in the original image A indicate standardized density levels, and the pixels in the shaded area of the binarized image B indicate black pixels.

First, in step (2), the binarized image is divided into unit areas UA of appropriate size. Here, it is divided into the same size as the dither matrix, that is, into a 4×4 size as shown in FIG. 2(c). Then, the number of black pixels in each unit area UA (
Alternatively, the number of white pixels) is counted (step ■).

Next, a partitioned area MA is formed by a plurality of adjacent unit areas UA (in this example, a matrix of KI x 2 x 2 horizontally), and for each partitioned area MA, variations in the number of black pixels within the unit area UA are Investigate (step ■). This variation ε
The value of is, for example, the deviation ( Use the one with the largest absolute value. and,
When this variation ε is less than a preset reference value of 60, the black pixel arrangement of the corresponding section area 1@MA is determined using a large-sized density matrix pattern, and when the variation ε is larger than the reference value ε0, The black pixel array of the corresponding divided area MA is determined using the density matrix pattern of the size (step 2).

To give a specific example, the numbers in FIG. 3(a) are the number of black pixels in each unit area UA, and the left partition area MA (M△1)
When the variation ε in is determined as described above, ε−0,5
Then, when the variation ε in the right partitioned area MA (MA2>) is calculated, it becomes ε-2,5.Here, the reference value ε
For example, if ε0=1.5, the divided area M A s
Then, it becomes ε0, and in the partition area di M A 2, ε〉
ε0. Therefore, in this embodiment, the divided area M A
A large-sized density matrix pattern is used in t, and a small-sized density matrix pattern is used in divided area M A 2 to find a black pixel array. For example, for the divided area M A s, a density matrix pattern with a size (8 x 8) corresponding to the divided area MA is used, and for the divided area M A 2, a density matrix pattern of the size (<4 x 4) corresponding to the unit area IJA is used. A black pixel array is determined using a density matrix pattern. Figure 4 (a) is used 81r! A density matrix pattern is copied onto each partitioned area MA based on the number of black pixels in a partition divided by the size of one matrix pattern (see Fig. 3 (b)), and the density matrix pattern in this example is is determined by comparing the dither matrix in Figure 5 (a) with the number of black pixels (corresponding to the density level) in each section in the case of an 8 x 8 size, and Regarding the size,
This is done by comparing the dither matrix shown in FIG. 5(b) with the number of black pixels in each section.

For example, in the case of a partition, the number of black pixels is 10, so
In the dither matrix shown in FIG. 5(B), the portions having a density level of 10 or less become black pixels, resulting in a density matrix pattern as shown in FIG. 4(B) described above.

Next, the black pixel array obtained in this way is shown, for example, in Figure 4 (
Divide into blocks BK of 4×4 size as shown in step (b)) to obtain a first density matrix pattern. Then, for each block, a new second density matrix pattern with a size corresponding to the enlargement/reduction magnification is obtained (
Step ■), and arrange them in block order to obtain an enlarged/reduced image (Step ■). FIG. 6(a) is an enlarged image obtained in this manner with an enlargement factor of 5/4, and FIG. 6(b) is a reduced image with a reduction factor of 3/4. Here, the first. Second
The size ratio of the 11a matrix pattern is according to the vertical and horizontal expansion/reduction magnification.The vertical and horizontal size of the second S degree matrix pattern is the vertical and horizontal size of the first density matrix pattern. It is multiplied by the reduction magnification. Therefore, in the example of FIG. 6 in which the vertical and horizontal magnifications are equal, the size in FIG. 6(A) is 5×5, and the size in FIG. 6(D) is 3×3.

In this example, for each block, when the mother pattern obtained by two-dimensionally arranging the first density matrix pattern is divided by the size of the second density matrix pattern, the same positional relationship is obtained. A certain pattern is cut out and used as the second density matrix pattern for the corresponding block. The seventh factor is an explanatory diagram showing an example of obtaining a second density matrix pattern from a first density matrix pattern (enlargement magnification 5/4
), the first density matrix pattern (S; I: C4X4> f) 70yr r t I* f t 2 #
r s3,...+'21+'22+...,...
21 Ft
s*..., F21, F221...,... is shown. First, as a second density matrix pattern corresponding to block F''tt, all blocks f11T'121'131...+f21+'2
2+...

. . uses a pattern cut out at the position of block Fst from a mother pattern that is assumed to contain the same first density matrix pattern corresponding to block fl1. Similarly, the second density matrix pattern corresponding to block F12 includes all blocks '11+'12+'13, . . . +f21+f22+.
..., the same first block corresponding to block f12
A pattern located at the position of block F12 is cut out from a mother pattern that is assumed to contain the density matrix pattern. That is, the second density matrix pattern corresponding to block F:j is all blocks rtt・F12・F13・°°°・F21・F22
, . . . use a pattern cut out at the position of block Fij from a mother pattern that is assumed to contain the same first density matrix pattern corresponding to block “1j”.

In addition, in step (2) above, if the number of black pixels obtained in step (2) is not used as is, but the modified black pixels obtained by using a spatial filter that takes into account the number of black pixels in the surrounding unit area, etc., are used. Image enhancement (filtering) can be performed at the same time. Furthermore, if the number of black pixels obtained in step (2) is converted to another number of black pixels based on a predetermined gradation conversion curve, gradation processing becomes possible. What kind of gradation processing is performed can be found in the gradation conversion song li! (The horizontal axis is the original black pixel count and the vertical axis is the converted black pixel count).

Furthermore, in the method of the present invention, in step 0, a part of the binarized 1ll pattern (corresponding to FIG. 2 (c)) obtained in step (2) is directly converted into the first density matrix pattern (small size). It can also be used as

Furthermore, a specific method for obtaining the pattern of each block after the above-mentioned scaling is to actually configure the above-mentioned mother pattern in memory and read data at a predetermined address from it to obtain the pattern. However, this method requires an extremely large memory capacity. Therefore, instead of actually creating a mother pattern, attention may be paid to the periodicity of the pattern, and the density of each pixel may be determined in the following manner to obtain a pattern after scaling.

That is, in the case of enlargement (magnification ■/n), the X-th pattern in the first block in the row direction of the new block (block after enlargement) is the same as the pattern in the first block in the row direction of the block before enlargement. , A[)1=Iod [X +l
Od[(I-1>(1-n>.

n]+1-2. The pattern in the y-th column in the 8th block in the column direction of the new block that is equal to the pattern in the 8th row in the column direction of the block before expansion is AC3-1 lod [y + g + od [ (
J-1) (m −n >.

n]+1-2. n ]+equal to the pattern in the 1st column, while reduced (magnification II/n)
In the case of [(1-1
> (n-In-fa l), n]+1-2. nl
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 +1st row, is AC3-IIIod [y +mod [(J −
1) (n −I n−ml ), n ]+1−
2. n ]+equal to the pattern in the first column.

Here, l1Od[p, Q] is the remainder of p÷q, and is naturally smaller than q.

Therefore, if you store the pixel density of each block before scaling in memory, you can easily update it by reading out the m degrees of pixels in the corresponding block using ADl and AC3 as addresses in the row and two column directions. You can get a pattern of blocks. Naturally, to obtain a same-sized pattern, the pixel density data of each block stored in this memory may be read out and used as is.

(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. In addition, by preparing density matrix patterns of multiple sizes, in divided areas where density changes are gradual,
By using a large-sized density matrix pattern and prioritizing gradation expression over resolution, in divided areas with sharp density changes,
On the contrary, since the resolution is given priority by using a small-sized density matrix pattern, both the illumination property and the resolution are excellent, and the detail in the enlarged image is improved.
) is never lost.

[Brief explanation of the drawing]

18th Flowchart showing an example of the method of the present invention, 2nd
The figure is an explanatory diagram showing an example of binarization, Fig. 3 is an explanatory diagram of divided regions, Fig. 4 is an explanatory diagram of block division, and Fig. 5 is an explanatory diagram of a dither matrix for obtaining the first density matrix pattern. FIG. 6 is an explanatory diagram of the second density matrix pattern (enlarged/reduced image), and FIG. 7 is an explanatory diagram of the method of obtaining the second density matrix pattern from the first density matrix pattern. A...Original image B...Binarized image UA...
-Unit area MA...divided area f11+f12.
...+f21. '22. ...Block F 11 + F I 2 of the first density matrix pattern
+..., F21 + F22,...
Second density matrix pattern block patent applicant Roku Konishi Photo Industry Co., Ltd. Agent Patent attorney Fuji Ijima 1 person M7 diagram

Claims (1)

[Claims] A binarized image is divided into unit areas, a predetermined number of adjacent unit areas form a partitioned area, and a large-sized density matrix pattern is used for the partitioned areas where the variation in the number of black pixels within the unit area is small. A black pixel array is determined, and a black pixel array is determined using a small-sized density matrix pattern for partitioned areas where the number of black pixels within a unit area varies widely, and then the black pixel array is divided into a plurality of blocks. For each block, assume a mother pattern in which the patterns are arranged two-dimensionally, and when the mother pattern is divided into sizes according to the enlargement/reduction magnification, patterns that have the same positional relationship are cut out and An image enlargement/reduction method characterized in that a reconstructed image obtained by using a pattern as a new pattern for each block is used as an enlarged/reduced image.
Reduction method.