JPH0416060A - Picture processor - Google Patents

Abstract

PURPOSE:To reduce ruggedness on an oblique line and to improve visual picture quality by calculating a mean density of a converted picture element in the case of applying magnification conversion to the picture element density of a binary picture, applying smoothing processing to the result and binarizing the result to output the converted picture. CONSTITUTION:A conversion picture element density arithmetic section 11 by the projection method applies density calculation of conversion picture ele ment to an input picture data 1a and a density data 1b (7-bit) is outputted to a smoothing filtering processing section 12. The smoothing filtering processing section 12 applies smoothing based on the density data 1b (7-bit) and outputs the smooth processing data 1c to a binarizing processing section 13. The binarizing processing section 13 binarizes the data 1c subject to smooth processing and outputs the conversion picture element 1d.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image processing device that performs resolution conversion and enlargement conversion of binary images in facsimile machines, image editing devices, and the like.

[Prior Art] Conventionally, it has been necessary to convert the pixel density of an image when mutual communication is required between image terminal devices having scanners, printers, etc. with different resolutions, or when image data is enlarged or reduced using an image editing device. There is.

In particular, various methods have been proposed as pixel density conversion methods for binary images, such as the spc method, the logical sum method, the 9-division method, the projection method, the linear interpolation method, and the distance inverse proportional method (Information Processing Society of Japan Paper V
OL, 25No. 5). Among these, the projection method is
It is known to be an excellent method with little geometric distortion due to conversion.

[Problems to be Solved by the Invention] However, in the above projection method, when enlarging conversion is performed, for example, when the image is enlarged twice as shown in FIG.
There was a problem that the jagged diagonal lines were noticeable and the images of characters etc. looked unnatural.

The present invention was made to solve the above problems, and
An object of the present invention is to provide an image processing device capable of reducing jaggedness of diagonal lines and improving visual image quality when enlarging and converting the pixel density of a binary image.

[Means for Solving the Problems] In order to achieve the above object, an image processing device of the present invention has the following configuration. That is, the image processing device is capable of converting the pixel density of a binary image at an arbitrary magnification, and includes a calculation means for calculating the average density of converted pixels when enlarging and converting the pixel density of the binary image, and a calculation means for calculating the average density of converted pixels; A smoothing means that performs smoothing processing on the result of the smoothing means, and a smoothing means that performs smoothing processing on the result of the smoothing means.
and a binarization means for converting into values.

[Operation] In the above configuration, when enlarging and converting the pixel density of a binary image, the average density of the converted pixels is calculated, the result is smoothed, and the converted image is compressed by being binarized. It works like this.

[Embodiment] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

Description of Structure (FIGS. 1 and 3)> FIG. 1 is a schematic block diagram showing the structure of a pixel density conversion device in this embodiment.

In the input image (original image 1a), for example, as shown in FIG. 3, after the page synchronization signal 31 rises, one line of image data 33 is synchronized with the line synchronization signal 32, and the image data 33 is synchronized with the image clock 34. is input. For this input image data 1a, a conversion pixel density calculation unit 11 using a projection method performs conversion pixel density calculation, and outputs density data 1b (7 bits) to a smoothing filtering processing unit 12.

In this smooth filtering processing section 12, the density data 1
Smoothing is performed based on data b (7 bits), and the smoothed data 1c is output to the binarization processing section 13. And 2
The digitization processing unit 13 binarizes the smoothed data lc and converts the converted pixels 1d into eight pixels.

Explanation of Projection Method (Fig. 4)> Next, details of each of the above-mentioned parts 11, 12, and 13 will be explained below.

First, the principle of the projection method will be explained with reference to FIG. In this embodiment, a case where the conversion magnification for both main scanning and sub-scanning is 3/2 will be described as an example.

Further, one pixel is defined as a rectangular area, and the converted pixel A, which is the pixel of interest, is projected onto the original pixel, and the original pixels having a pixel surface that overlaps with the pixel surface of A on the projection plane are P, 0, . Let them be R and S.

Here, within the pixel plane of the projected converted pixel A, P, O, R
, S are the areas occupied by the pixel planes Sp, So, respectively.
So, Ss is the average density of the pixel of interest.

is expressed by the following equation.

However, Ip, I. , Ip, Is are P, Q, R
, S is the concentration at each point.

<Description of each processing section (FIGS. 5 to 9)> Next, the configuration of the converted pixel density calculation section 11 will be described below with reference to the block diagram shown in FIG. 5.

In the example shown, it is possible to process a range of approximately conversion magnification>l/2.

In the figure, numeral 51 denotes a pixel number pressure unit, which extracts neighboring original pixels at the position of the converted pixel on the projection plane (<X, Y). Reference numeral 52 denotes a converted pixel position calculation unit, which calculates the position of the converted pixel on the projection plane determined according to the conversion magnification (p, q) in each of the main scanning and sub-scanning directions. Reference numeral 53 denotes an area calculation section, which calculates each area according to the position information and conversion magnification obtained by the converted pixel position calculation section 52. Reference numeral 54 denotes an arithmetic processing section that performs the calculation of equation (1), which multiplies the outputs from the pixel extraction section 51 and the area calculation section 53 to calculate density data 1b of the target converted pixel.

Note that the converted pixel density calculation section 21 is not limited to the above-mentioned configuration (in general, any configuration may be used as long as the calculation result expressed by the following equation (2) can be obtained.

Here, IN is the average density or average brightness of the converted pixel n of interest, and ■ is the density or brightness of an original pixel having a pixel surface that overlaps the pixel surface of the pixel of interest n on the projection plane. 8 is an area of the pixel surface of the original pixel that overlaps with the pixel surface of the converted pixel n.

In this embodiment, in order to simplify the circuit, the number of referenced original pixels SK is limited to four.

By increasing the number of reference pixels, it is possible to widen the range of conversion magnification that can be processed (minimum magnification during reduction).

Furthermore, as described above, the pixel extraction unit 51 in this embodiment is
It is possible to process not only sequentially input image data 1a but also original image data stored in a storage device such as a memory.

In the conventional projection method, a converted image is obtained by simply binarizing the density data 1b obtained here. FIG. 6 is a diagram showing a specific example of a magnification of 2.5 times using a conventional projection method. In the figure, the converted pixel density (ratio) shown at 62 obtained from the original image shown at 61 by the projection method is converted into the figure shown at 63 by performing simple binarization processing using threshold expansion. . Therefore, if the original image 61 is a part of the diagonal line, it will be enlarged and the jagged edges will become noticeable.

On the other hand, in this embodiment, as shown in FIG. 7, the converted pixel density 73 obtained from the original image 71 by the projection method is smoothed by performing the binarization process after performing the smoothing filtering process. A converted image can be obtained.

Here, in the case of the example shown in FIG. 7, the coefficient average value filter shown in FIG. 8 is used as the smoothing filter. That is, when the density of the pixel of interest is P, the data P' after filtering processing is expressed by the following equation (3).

P' = (2P+A+B+C+D+E+F+
G+)I) / 10... (3)A
-H indicates the density of the neighboring pixel of the pixel P.

Next, the configuration of the smooth filtering processing section 12 in this embodiment will be described below with reference to the block diagram shown in FIG. 9.

In the figure, 91a and 91b are one-line delay processing units, and 91a to 91f are one-pixel delay elements. and,
This l line delay processing section 91a.

The image data string 33 shown in FIG. 3 is serially input to the pixel delay elements 91b and 1-pixel delay elements 91a to 91f, and the pixel of interest P and its surrounding pixels A to H are taken out.

Reference numeral 93 denotes a filtering calculation section, in which, in the case of the filter coefficients shown in FIG. 8, the calculation process expressed by the above-mentioned equation (3) is performed, and the smoothed data P' is compressed.

After the above processing, the ratio data string P' is input to the binarization processing section 13, where it is compared with a predetermined threshold value, binarized, and output as a converted image 1d.

According to this embodiment described above, in a pixel density conversion device for two images using a projection method, smoothing filtering processing is performed on density data of converted pixels during enlargement conversion, and smoothing processing is performed after conversion. This makes it possible to obtain a high-quality image with less jaggedness in the shaded areas.

Furthermore, by setting appropriate filter coefficients according to the conversion magnification, it is possible to perform good smoothing processing for enlargement conversion at any magnification.

In this embodiment, the smoothing process was performed using the filter shown in FIG. 8, but the present invention is not limited to this, and any smoothing filter depending on the conversion magnification may be used.

[Effects of the Invention] As described above, according to the present invention, when the pixel densities of two images are enlarged and converted, jaggedness of diagonal lines can be reduced and a high-quality image can be obtained.

[Brief explanation of drawings]

Figure 1 is a schematic block diagram showing the configuration of the pixel density conversion device in this embodiment, Figure 2 is a diagram explaining conventional enlargement conversion, Figure 3 is a diagram showing the timing of input images, and Figure 4 is projection. Fig. 5 is a block diagram showing the configuration of the converted pixel density calculation section, Fig. 6 is a diagram showing conventional enlargement conversion, and Fig. 7 shows enlargement conversion in this embodiment. FIG. 8 is a diagram showing a smoothing filter in this embodiment, and FIG. 9 is a block diagram showing the configuration of a smoothing filtering processing section in this embodiment. In the figure, 11...conversion pixel density calculation section, 12...smoothing filtering processing section, 13...binarization processing section. Patent a applicant Canon Co., Ltd. No. 6”J Hayabusa, Betsu (2iiiihi) (L gi ＼115l/2
), Mottomo to hire the dead tongue and tiger mountain; Seven guests 311. Cap fruit 7th figure 8th figure dried; Bone filter evil! ,Mu1 fruit (Jin!1)i1i1/2)

Claims (1)

[Scope of Claims] An image processing device capable of converting the pixel density of a binary image at an arbitrary magnification, comprising a calculation means for calculating the average density of converted pixels when enlarging and converting the pixel density of the binary image. An image processing device comprising: a smoothing unit that performs smoothing processing on the result of the arithmetic unit; and a binarization unit that binarizes the result of the smoothing unit.