JP3358133B2 - Image processing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus for converting binary image information in which a character image and a picture image are mixed into multi-value image information.

[0002]

2. Description of the Related Art Generally, in a facsimile apparatus and an image filing system, an original binary image such as a character or a figure (hereinafter referred to as a character image), a halftone image such as a picture or a photograph (hereinafter referred to as a picture image), Both are transmitted and stored as black and white binary image information. In this case, the picture image is read in multi-values and binarized by pseudo halftone processing such as dither processing.

On the other hand, in recent years, a multi-value plotter capable of recording not only black and white but also a grayscale image with a fixed number of gradations has been put to practical use. Such a multi-value plotter may record binary image information in which a character image and a picture image are mixed.

In this case, the character image area and the picture image area of the binary image information are distinguished, and in the character image area, the pixel density of the outline of the character is corrected to an intermediate density, and the outline of the outline is jagged. A correction process was performed to make certain jaggies inconspicuous. For the picture image area, for example,
As disclosed in Japanese Patent Application Laid-Open No. 1-282967, a smoothing process is performed in which each pixel is multi-valued to express an intermediate density.

Conventionally, the distinction between the character image area and the picture image area of the binary image information has been executed by the following method, for example.

One method is to sequentially focus attention on a certain range of image areas in the binary image information and determine the periodicity of the black and white change of the pixels in each area. For example, when white pixels and black pixels are alternately changed by a certain number or more in one area, the one area is determined to be a dither-processed picture image portion. It is determined to be a part.

Another method is to pay attention to each pixel of the binary image information and make a determination based on the correlation between the pixel of interest and eight adjacent pixels. For example, when there are four or more adjacent pixels of the same color as the target pixel, the target pixel is determined to be a character image portion, and otherwise, it is determined to be a picture image portion.

In each of these determination methods, it is necessary to read binary image information one pixel at a time, or to count the number of pixels that meet the conditions, which complicates the hardware and software of the image processing apparatus. Was.

[0009]

As described above, conventionally, when the correction processing of the outline part of a character and the smoothing processing of a picture image part are performed on the binary image information, the binary image information is not used. It is necessary to distinguish between the character image area and the picture image area of
There is a problem that hardware and software of the image processing apparatus become complicated due to the determination process.

An object of the present invention is to provide an image processing apparatus which solves the above-mentioned problem and can execute the correction processing of the outline portion of the character and the smoothing processing of the picture image portion by simple hardware or software. Aim.

[0011]

For this purpose, the present invention is directed to binary image information in which a character image and a picture image are mixed.
In an image processing apparatus that executes density correction processing of a contour part of a character and density smoothing processing of a picture image part and outputs multi-valued image information, binary matrix data of a fixed size is
A storage unit for storing a plurality of binary image information in a case where the binary image information has a high resolution and a case in which the binary image information is a low resolution; and a fixed unit including a pixel of interest focusing on each pixel of the binary image information. Image information extracting means for sequentially extracting binary image information of a range, and a plurality of binary image information stored with the extracted binary image information.
If the resolution of the binary image information is high at this time, the extracted
When the pixel matching range between the value image information and the binary matrix data is set to be wide, and when the resolution is low, the binary matrix data is set according to the resolution of the binary image information in order to set the pixel matching range to be narrow. A pixel region determining means for determining whether or not the target pixel corresponds to a contour portion of a character by selecting and sequentially comparing the target pixel, and a pixel region determining means for determining whether or not the target pixel corresponds to a contour portion of the character. Means for executing the density correction processing, and means for executing the density smoothing processing on the pixel of interest when the pixel of interest does not correspond to a contour portion of a character. Further, image processing for executing density correction processing of a contour portion of a character and density smoothing processing of a picture image portion on binary image information in which a character image and a picture image are mixed and outputting the multivalued image information In the apparatus, storage means for storing a plurality of binary matrix data of a predetermined size in advance, and image information extracting means for sequentially extracting binary image information in a predetermined range including the pixel of interest by focusing on each pixel of the binary image information A pixel area determining means for sequentially checking the extracted binary image information with a plurality of stored binary matrix data to determine whether the pixel of interest corresponds to a contour part of a character; Means for executing the density correction processing on the target pixel when the target pixel corresponds to the outline of the character; and performing the above-described density correction on the target pixel when the target pixel does not correspond to the outline of the character. Dark When the smoothing process is executed and the resolution of the binary image information is high at this time, the specific gravity for reflecting the surrounding pixel density on the target pixel density is set small, and when the resolution is low, the specific gravity is set large. Means for setting and executing the density smoothing process.

[0012]

The distinction processing between the character image area and the picture image area of the binary image information, which has been conventionally performed, becomes unnecessary, and whether or not the pixel of interest corresponds to the outline of the character is determined by a simple data collation. It is executed by processing. This makes it possible to execute the correction process of the outline portion of the character and the smoothing process of the picture image portion with simple hardware and software. Further, it is possible to determine whether or not the pixel of interest corresponds to the outline of the character according to the resolution of the binary image information, and the determination accuracy is improved. Furthermore, density smoothing can be performed according to the resolution of the binary image information, and the image quality can be improved.

[0013]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an image processing apparatus according to an embodiment of the present invention. In the figure, a memory 1 temporarily stores inputted binary image information. In this memory 1, binary image information in which a character image and a picture image are mixed in one page is stored. When the image of interest corresponds to a certain position of the outline of the character, the character outline correction unit 2 converts the pixel of interest to a certain intermediate density and outputs it as multi-tone image information. The smoothing unit 3 corrects the density of each pixel other than the outline portion of the character and outputs it as multi-tone image information.
The switching circuit 4 outputs the output of the character outline correction unit 2 or the smoothing unit 3.
Is selected. The multi-valued plotter 5 records and outputs a grayscale image on a recording sheet with a fixed number of gradations.

The area discrimination data table 6 is a memory that stores various pixel patterns of a predetermined range of binary image information as matrix data. The collation unit 7 collates the image information read from the memory 1 with the matrix data read from the area determination data table 6.

With the above arrangement, the binary image information is input to the image processing apparatus of this embodiment in one of two resolutions, high and low. At the time of input, the level of the resolution is indicated by a predetermined signal from outside.

The image processing apparatus temporarily stores the input binary image information in the memory 1. This binary image information is, for example,
As shown in FIG. 2, the character image C and the picture image P are mixed in one page. This binary image information is obtained by binarizing multi-value image information from the beginning. When binarizing, it is assumed that the character image portion has been subjected to a known enhancement process for clarifying the outline of the character. It is also assumed that the picture image portion has been binarized by a known pseudo halftone process such as a dither method.

As shown in FIG. 3, two sets of matrix data groups 61 and 62 are stored in the area discrimination data table 6. Matrix data groups 61 and 62 of each set
Is a group of a plurality of 5 × 5 matrix data. The figure shows an example of matrix data in each set, where "1" or "0" indicates valid data, and "x" indicates invalid data that may be "1" or "0". ing. As described above, each piece of matrix data includes a certain range of valid data and other invalid data.

If the binary image information is input at the higher resolution of the two types, the matrix data group 61
Is selected, and when the input is made at the lower resolution, the matrix data group 62 is selected.

When the binary image information has been stored in the memory 1, the image processing apparatus pays attention to each pixel of the stored image information, and stores a predetermined range of image information of 5 pixels in the vertical and horizontal directions including the pixel of interest. Read sequentially from 1.

The collating unit 7 inputs one of the matrix data groups 61 selected from the read image information of a certain range and the area discrimination data table 6. Then, the input image information is sequentially collated with the valid data of each matrix data.

For example, in the case of the matrix data illustrated in FIG. 3, when the image information in a certain range read from the memory 1 corresponds to the upper edge contour portion of the oblique line rising to the right, the image information And the valid data of the matrix data match. In this embodiment, the matrix data group 6
Such various matrix data are set in 1, 62.

Thus, when the pixel of interest corresponds to the outline of a character, the collating unit 7 matches the image information with the valid data of the matrix data.

The collation unit 7 switches the switching circuit 4 to the character outline correction unit 2 when the collation results match.

The character outline correction unit 2 corrects the density to a constant intermediate density only when the pixel of interest is a white pixel at the hatched edge,
No correction is made in other cases. For example, as shown in FIG. 4A, when the target pixel A corresponds to the oblique edge of the character outline, the correction is made to the intermediate density as shown in FIG. 4B.
As a result, the correction is performed so that the jaggy in the hatched portion of the image is not noticeable. On the other hand, for example, if the contour is in the horizontal direction as shown in FIG. The same applies when the contour is vertical.

The character outline correction section 2 outputs the image information corrected in this way as multi-valued image information. The multi-value image information is input to the multi-value plotter 5 via the switching circuit 4.

On the other hand, when the image information and the valid data of the matrix data do not match, the collating unit 7 switches the switching circuit 4 to the smoothing unit 3 side.

The smoothing unit 3 corrects the density of the target pixel based on surrounding pixels.

Next, the correction process will be described. Smoothing part 3
As shown in FIG. 5, there are two types of matrix data 31 and 32 for smoothing processing. When the resolution of the binary image information is high, the matrix data 31 is selected. When the resolution is low, the matrix data 3 is selected.
2 is selected.

Here, each value of the selected matrix data for smoothing processing is assumed to be A to I as shown in FIG. Further, as shown in FIG. 2B, among the image information in a certain range read from the memory 1, the pixel densities corresponding to the matrix are a to i.

The smoothing unit 3 corrects the pixel of interest e to an average density e 'in the above-mentioned fixed range by the following equation based on the values A to I and the pixel densities a to i. e ′ = (a × A + b × B + c × C + d × D + e × E + f
× F + g × G + h × H + i × I) / T where T is the total value of the above values A to I.

As a result, in the picture image area of the picture information, each pixel is corrected to an intermediate density.

The smoothing section 3 outputs the image information corrected in this way as multi-valued image information. The multi-value image information is input to the multi-value plotter 5 via the switching circuit 4. The multi-value plotter 5 records the input multi-value image information on a recording sheet as a gray image.

As described above, in this embodiment, attention is paid to each pixel of the binary image information, binary image information in a certain range including the pixel of interest is sequentially extracted, and the extracted binary image information is stored in advance. It is determined whether or not the pixel of interest corresponds to the outline of the character by comparing it with the matrix data of the character. If the image of interest corresponds to the outline of the character, the character outline correction unit 2 performs While the correction is made to the intermediate density, in other cases, the smoothing unit 3 executes the smoothing process.

Accordingly, the process of discriminating between the character image area and the picture image area of the binary image information, which has been conventionally performed, becomes unnecessary. Whether the pixel of interest corresponds to the outline of the character is determined by
It is executed by a simple process called data collation. This makes it possible to execute the correction process of the outline portion of the character and the smoothing process of the picture image portion with simple hardware and software.

In the correction process of the outline of the character,
Since the pixels at the shaded edge of the character outline are corrected to the intermediate density,
The jaggedness of the character outline becomes inconspicuous, and in the smoothing process of the picture image portion, each pixel is corrected to an intermediate density, so that the image quality of the recorded image is improved as a whole.

When the resolution of the image information is high, the matrix data group 61 is used, and when the resolution is low, the matrix data group 62 is used.

When the resolution is low, the number of pixels in the white area and the black area of the image information in the outline of the character is reduced. In this case, if matrix data for detecting a wide range of white area and black area, such as the matrix data group 61, is used, the image information and the matrix data will not match even in the outline part of the character, and the pixel of the outline part Density correction cannot be performed. In this case, by using the matrix data for detecting the white area and the black area in a relatively narrow range like the matrix data group 62, the outline of the character is correctly detected, and the density correction of the pixels of the outline is executed. Will be able to

The smoothing unit 3 uses the matrix data 31 when the resolution of the image information is high, and uses the matrix data 32 when the resolution is low.

In the matrix data 31, since the data value of the surrounding pixel is smaller than the data value of the target pixel, the specific gravity for reflecting the surrounding pixel density on the target pixel density becomes smaller. When the resolution of the image information is high, a good gray-scale image can be obtained by such correction.

On the other hand, in the matrix data 32, since the data value of the target pixel and that of the surrounding pixels are the same, the specific gravity for reflecting the density of the surrounding pixels on the density of the target pixel increases. When the resolution of the image information is low, a good gray-scale image can be obtained by such correction.

In the above embodiment, the character outline correction unit 2 corrects the white pixels in the outline to gray with a constant density, but sets different densities according to the pixel pattern of the surrounding pixels. It may be.

Although an example has been described in which a multi-valued image converted from a binary image is recorded on recording paper by the multi-valued plotter 5, it is natural that the same applies to a case where a screen is displayed on a display device.

[0044]

As described above, according to the present invention, by focusing on each pixel of the binary image information, the binary image information of a predetermined range including the pixel of interest is sequentially extracted, and the extracted binary image information and the extracted binary image information are determined in advance. The stored pixel data is compared with the stored matrix data to determine whether or not the pixel of interest corresponds to the outline of the character. If the pixel of interest corresponds to the outline of the character, a predetermined correction process is performed. When the pixel does not correspond to the outline portion of the character, the smoothing process is executed, so that the correction process of the outline portion of the character and the smoothing process of the picture image portion can be executed by simple hardware and software. Become like Further, it is possible to determine whether or not the pixel of interest corresponds to the outline of the character according to the resolution of the binary image information, and the determination accuracy is improved. Furthermore, density smoothing can be performed according to the resolution of the binary image information, and the image quality can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram of an image processing apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of image information to be processed.

FIG. 3 is an explanatory diagram of matrix data for area determination.

FIG. 4 is an explanatory diagram of an operation of a character outline correction unit.

FIG. 5 is an explanatory diagram of matrix data for smoothing processing.

FIG. 6 is an explanatory diagram showing correspondence between image information and matrix data at the time of smoothing processing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Memory 2 Character outline correction part 3 Smoothing part 4 Switching circuit 5 Multi-valued plotter 6 Area discrimination data table 7 Matching part 31, 32 Matrix data 61, 61, 62 Matrix data group

Claims (2)

(57) [Claims] 1. A binary image information in which a character image and a picture image are mixed is subjected to a density correction process for a contour portion of a character and a density smoothing process for a picture image portion and output as multi-valued image information. Storage means for storing a plurality of pieces of binary matrix data of a fixed size in advance in a case where the binary image information has a high resolution and a case in which the binary image information has a low resolution. Image information extracting means for sequentially extracting binary image information in a certain range including the pixel of interest while paying attention to each pixel of the binary image information; and a plurality of binary matrix data storing the extracted binary image information And if the resolution of the binary image information is high at this time, the pixel matching range between the extracted binary image information and the binary matrix data is set wide, and the resolution is low. The pixel matching range A pixel area discriminating means for discriminating whether or not the pixel of interest corresponds to a contour portion of a character by selecting the binary matrix data in accordance with the resolution of the binary image information and sequentially collating the binary matrix data so as to set the frame to be narrow; Means for executing the density correction processing on the pixel of interest when the pixel of interest corresponds to a contour portion of a character; Means for performing the density smoothing process on the other hand. 2. A binary image information in which a character image and a picture image are mixed is subjected to a density correction process for a contour portion of a character and a density smoothing process for a picture image portion and output as multi-valued image information. Storage means for storing a plurality of binary matrix data of a predetermined size in advance; and an image for sequentially extracting a predetermined range of binary image information including the pixel of interest by focusing on each pixel of the binary image information. Information extracting means; and pixel area determining means for determining whether the pixel of interest corresponds to a contour portion of a character by sequentially comparing the extracted binary image information with a plurality of stored binary matrix data. Means for executing the density correction processing on the pixel of interest when the pixel of interest corresponds to a contour portion of a character; versus Te Perform the density smoothing, and,
At this time, if the resolution of the binary image information is high, the specific gravity for reflecting the surrounding pixel density on the target pixel density is set small,
Means for setting the specific gravity to be large when the resolution is low, and executing the density smoothing process.